Nanomedicine in pulmonary delivery

Abstract

The lung is an attractive target for drug delivery due to noninvasive administration via inhalation aerosols, avoidance of first-pass metabolism, direct delivery to the site of action for the treatment of respiratory diseases, and the availability of a huge surface area for local drug action and systemic absorption of drug. Colloidal carriers (ie, nanocarrier systems) in pulmonary drug delivery offer many advantages such as the potential to achieve relatively uniform distribution of drug dose among the alveoli, achievement of improved solubility of the drug from its own aqueous solubility, a sustained drug release which consequently reduces dosing frequency, improves patient compliance, decreases incidence of side effects, and the potential of drug internalization by cells. This review focuses on the current status and explores the potential of colloidal carriers (ie, nanocarrier systems) in pulmonary drug delivery with special attention to their pharmaceutical aspects. Manufacturing processes, in vitro/in vivo evaluation methods, and regulatory/toxicity issues of nanomedicines in pulmonary delivery are also discussed.

Full text

© 2009 Mansour et al, publisher and licensee Dove Medical Press Ltd. This is an Open Access article
which permits unrestricted noncommercial use, provided the original work is properly cited.
International Journal of Nanomedicine 2009:4 299–319
International Journal of Nanomedicine
299
REVIEW
Dovepress
open access to scientific and medical research
Open Access Full Text Article
submit your manuscript | www.dovepress.com
Dovepress
Nanomedicine in pulmonary delivery
Heidi M Mansour
Yun-Seok Rhee
Xiao Wu
University of Kentucky,
College of Pharmacy, Division
of Pharmaceutical Sciences-Drug
Development Division, Lexington,
KY, USA
Correspondence: Heidi M Mansour
Assistant Professor of Pharmaceutical
Sciences and Pharmaceutical Technology,
University of Kentucky, College of
Pharmacy, Division of Pharmaceutical
Sciences-Drug Development Division, 725
Rose Street, Lexington, KY 40536, USA
Tel +1 859 257 1571
Email heidi.mansour@uky.edu
Abstract: The lung is an attractive target for drug delivery due to noninvasive administration
via inhalation aerosols, avoidance of first-pass metabolism, direct delivery to the site of action
for the treatment of respiratory diseases, and the availability of a huge surface area for local
drug action and systemic absorption of drug. Colloidal carriers (ie, nanocarrier systems) in pul-
monary drug delivery offer many advantages such as the potential to achieve relatively uniform
distribution of drug dose among the alveoli, achievement of improved solubility of the drug
from its own aqueous solubility, a sustained drug release which consequently reduces dosing
frequency, improves patient compliance, decreases incidence of side effects, and the potential of
drug internalization by cells. This review focuses on the current status and explores the potential
of colloidal carriers (ie, nanocarrier systems) in pulmonary drug delivery with special attention
to their pharmaceutical aspects. Manufacturing processes, in vitro/in vivo evaluation methods,
and regulatory/toxicity issues of nanomedicines in pulmonary delivery are also discussed.
Keywords: pulmonary delivery, colloidal carriers, nanocarrier systems, liposome, polymeric
nanoparticle, solid lipid nanoparticle, submicron emulsion, dendrimer
Introduction
Burgeoning interest in colloidal carriers (nanocarrier systems) has led to increasing
attention for pulmonary drug delivery. The lung is an attractive target for drug delivery
due to noninvasive means to provide not only local lung effects but possibly high
systemic bioavailability, avoidance of first-pass metabolism, more rapid onset of
therapeutic action, and the availability of a huge surface area.1,2 Nanocarrier systems
in pulmonary drug delivery offer many advantages. These advantages include the
following: 1) the potential to achieve relatively uniform distribution of drug dose
among the alveoli; 2) an achievement of enhanced solubility of the drug than its
own aqueous solubility; 3) the sustained-release of drug which consequently reduces
the dosing frequency; 4) suitability for delivery of macromolecules; 5) decreased
incidence of side effects; 6) improved patient compliance; and 7) the potential of drug
internalization by cells.3,4
Nanotechnology has been described as the manipulation, precision placement,
measurement, modeling or manufacture of matter in the sub-100 nm range,5 although,
depending on the context, the term sometimes identifies particles in the 1 to 200 nm
range.3,6 However, the 100 nm limit is constraining, as in effect it would disregard
many recent achievements and a plethora of basic science (interfacial and colloidal
chemistry) literature and pharmaceutical research literature reports. In addition, there
are a number of literature reports in both the basic science and pharmaceutical literature
Number of times this article has been viewed
This article was published in the following Dove Press journal:
International Journal of Nanomedicine
4 December 2009

International Journal of Nanomedicine 2009:4
300
Mansour et al Dovepress
submit your manuscript | www.dovepress.com
Dovepress
which scientifically define dimensions of nanoparticles
ranging in size from 1 to 1000 nm.3,7–9 In drug delivery
systems, submicron size is significant because biodistribu-
tion of submicron particles are critical and some safety issues
may be occurred when we use microparticles. For instance,
after intravenous injection of parenteral formulation, large
particles (5 µm) can cause pulmonary embolism, which
can induce fatal results,10,11 therefore submicron particle size
is required for parenteral formulations. Although the upper
limit of particle size for ophthalmic application is about 5 µm,
the optimum particle size is less than 1,000 nm because a
scratching feeling can occur when microparticles are applied
to the eyes.12 Phagocytosis is sensitive to particle size, and it
is generally thought that particles of 0.5–3 µm in diameter
are taken up by macrophages,13 and particles of less than
0.26 µm can escape from phagocytosis by macrophages.1
Phagocytosis is also the main mechanism responsible for
the rapid clearance of particulate drug delivery systems from
the body. Furthermore, cytosolic delivery of drugs can be
achieved by endocytosis of submicron drug carriers. There-
fore, in this review, the authors consider all particulates for
which at least one dimension is 1–1000 nm.
There are numerous applications for nanotechnology,
however, especially the treatment, diagnosis, monitoring and
control of biological systems have recently been referred to as
‘‘nanomedicine’’ by the National Institutes of Health (Bethesda,
MD, USA).14 In short, nanomedicine is the application of nano-
technology to medicine, and two main types of nanomedicine
products are currently in clinical trials: diagnostic tests and
drug delivery devices.15 Over the past decades, efforts have
been focused on the development of nanomedicines such as
nanoparticles, liposomes, nanoemulsions, or dendrimers for the
specific delivery of drugs to the target tissues.
The modern inhalation devices can be divided into
three different categories, nebulizers, pressurized metered
dose inhalers (pMDI), and dry powder inhalers (DPI).1
In most cases, nanocarriers can be delivered to the lungs by
nebulization of colloidal dispersions or using pMDIs and
DPIs in solid form.1,3 Due to small size and strong particle-
particle interactions of nanocarriers, particle agglomeration
and settlement can occur in colloidal dispersions. Moreover,
chemical instability of colloidal dispersions is another issue
owing to carrier hydrolysis and drug degradation. To improve
physical and chemical instability of nanocarrier dispersions,
freeze-drying of nanocarriers has been explored as a means
to provide a storage form. However, redispersibility and the
use of stabilizers for lyophilization are still problematic in
nebulization. The use of a nanocarrier itself for delivery to
lungs is severely limited because individual nanocarriers do
not deposit efficiently in the lungs by diffusion, sedimentation
or impaction, which results in the exhalation of a majority
of the inhaled dose.3 Therefore, micron-sized powder carri-
ers containing nanoparticles or agglomerated nanoparticles
were designed to improve the inhalation aerosol delivery
of nanoparticles for deep lung delivery by using MDIs and
DPIs.1 A thorough discussion of incorporating nanopar-
ticles into micron-scale structures or processing methods
for agglomerated nanoparticles are beyond the scope of
this review, but the topic has been recently reviewed else-
where.3,4,16
This review focuses on the current status and explores
the potential of colloidal carriers (nanocarrier systems) in
pulmonary drug delivery with special attention to and in
depth presentation of their pharmaceutical aspects. Manu-
facturing processes, in vitro/in vivo evaluation methods, and
regulatory/toxicity issues of nanomedicines in pulmonary
delivery are also presented and discussed.
Drugs for inhalation
Various drugs are investigated for local or systemic
pulmonary delivery.2 These include small molecules, protein/
peptide drug and genes (Table 1). In case of small molecule
drugs, many studies were focused on local application for the
treatment of chronic respiratory diseases such as asthma and
chronic obstructive pulmonary disease (COPD). However,
pulmonary protein/peptide delivery offers great potential for
both local targeting for the treatment of respiratory diseases
and systemic targeting for the treatment of diabetes mellitus
or thrombosis. Gene delivery to the lungs are mainly focused
on the localized delivery of drugs to the site of disease, the
lungs and airways, including lung cancer, genetic disorders
affecting the airways (cystic fibrosis, alpha-1-antitrypsin defi-
ciency), obstructive lung diseases (asthma), and vaccination.
Since original aerosol technology was developed for small
molecule drugs, it is necessary to evolve the reengineering
of nanocarrier self-assembly systems for macromolecular
pulmonary delivery.17 Examples of drugs for pulmonary
nanocarrier systems are shown in Figure 1.18–28,29–76
Nanocarrier systems for pulmonary
drug delivery
Polymeric nanoparticulate pulmonary
delivery
Polymeric nanoparticles are widely studied in drug
delivery system for parenteral administration;77,78 however

International Journal of Nanomedicine 2009:4 301
Nanomedicine in pulmonary delivery
Dovepress
submit your manuscript | www.dovepress.com
Dovepress
Table 1 Examples of drugs for pulmonary delivery using colloidal carrier self-assembly systems
Therapeutic areas and drugs Drug typesaColloidal carrier self-assembly
systems and referencesb
Asthma (anti-inammatory)
Budesonide S LP,2,3 DN4,5
Syk antisense oligodeoxynucleotides G LP6
Ketotifen S LP7
Ibuprofen S DN8
Interleukin-4 antisense oligodeoxynucleotides G PN9
Indomethacin, ketoprofen S SLN10
Vasoactive intestinal peptide P LP,11–13 PN14
Dexamethasone palmitate S LP15
Fluticasone S DN5
Pulmonary hypertension
Vasoactive intestinal peptidecP LP,11–13 PN14
Vascular endothelial growth factor (VEGF) gene G LP16
Nuclear factor kB decoy oligodeoxynucleotides G NP17
Nifedipine S DN18
Cystic brosis
Amiloride hydrochloride S LP19
Secretory leukocyte protease inhibitor P LP20
Infections
Tobramycin S LP,21,22 DN23
Rifampicin S LP,24–27 PN,28–31 SLN32
Isoniazid, pyrazinamide S PN,28,29 LP,27 SLN32
Ciprooxacin S LP33,34
Amphotericin B S LP35,36
Itraconazole S DN37–40
Lung cancers
Interleukin-2 P LP41
p53 gene G PN42–45
9-nitrocamptothecin S LP46
Leuprolide P LP47
Doxorubicin S PN48
Programmed cell death protein 4 (PDCD4) P PN49,50
Antisense oligonucleotide 2’-O-methyl-RNA G PN51
Akt1 (protein kinase B) siRNA G PN52,53
6-{[2-(dimethylamino)ethyl]amino}-3-hydroxyl-7H-indeno[2,1-c]
quinolin-7-one dihydrochloride
S PN54
Mutative defects in lung
Chimeric oligonucleotide G PN55
Immune modulators
Cyclosporine A P LP,56 DN57,58
Tacrolimus S LP59
Vaccination
HLA-A*0201-restricted T-cell epitopes from Mycobacterium tuberculosis G PN60
V1Jns plasmid encoding antigen 85B from M. tuberculosis G SE61
Reactive oxygen species mediated diseases
Superoxide dismutase P LP62–64
(Continued)

International Journal of Nanomedicine 2009:4
302
Mansour et al Dovepress
submit your manuscript | www.dovepress.com
Dovepress
their application to the pulmonary routes are also widely
recognized.4 The main roles of polymeric nanoparticles
in drug delivery system are to carry the drug molecules,
to protect drugs from degradation, and to control drug
release.78 Therapeutically used polymeric nanoparticles are
composed of biodegradable or biocompatible materials,
such as poly(ε-caprolactone) (PCL), poly(lactic acid)
(PLA), poly(lactic-co-glycolic acid) (PLGA), alginic acid,
gelatin and chitosan. Various polymers for pulmonary
drug delivery using nanocarrier systems are shown in
Table 2. The chemical structures of polymers for polymeric
nanoparticles used in pulmonary delivery systems are shown
Figure 2.26,29,38,39,54–57,59,61,69,70,74,75,79–93
Due to their biocompatibility, surface modification
capability, and sustained-release properties, polymeric
nanoparticles are intensively studied using various impor-
tant pulmonary drugs. These pulmonary drug include anti-
asthmatic drugs,22,26 antituberculosis drugs,38,39 pulmonary
hypertension drugs,29 and anticancer drugs.54 However, to
avoid accumulation of polymer carriers following repeated
dosing, the biodegradability and toxicity of polymers over
the long term should be closely examined in the formula-
tion of polymeric nanoparticles for pulmonary delivery.
Additionally, in vitro lung surfactant models and in vivo
studies are required to establish the pulmonary acceptability
of polymeric nanocarrier systems, as polymers and their
degradation products can affect the vital surfactant properties
in the alveoli which in turn will affect pulmonary immunity
control and adversely affect the work of breathing.
Although cationic lipid-based gene carriers are currently
being clinically evaluated further than polymer-based gene
carriers,94 cationic polymers are one of the popular carriers
for gene delivery to the lungs.95,96 Although polyethylenei-
mine (PEI) and polyamino acids, such as poly-l-lysine, have
been shown to be effective agents for DNA delivery both
in vitro and in vivo,97,98 cytotoxicity99 and low transfection
efficacy problems when delivered via inhalation have to be
overcome.100 To solve these problems, various modifica-
tions of PEI with liposomes/PEGs or conjugations of PEI
with ligands such as transferrin have been investigated
extensively.101–107 Noninvasive pulmonary gene delivery using
cationic polymers has been reviewed in detail elsewhere.95
Liposomal pulmonary delivery
Liposomes are one of the most extensively investigated
systems for controlled delivery of drug to the lung.108
Liposomes seem particularly appropriate for therapeutic
agent delivery to lung, since these vesicles can be prepared
from compounds endogenous to the lungs, such as the
components of lung surfactant, and these properties make
liposomes attractive candidates as drug delivery vehicles.37
The first pharmaceutical liposomal products in market
include the synthetic lung surfactant Alveofact® (Dr Karl
Thomae GmbH, Biberach, Germany) for pulmonary instil-
lation for the treatment of respiratory distress syndrome
(RDS).109 Typically, liposomal formulations have been
delivered to the lung in the liquid state, and nebulizers have
been used extensively for the aerosol delivery of liposomes
in the liquid state.110 However, concerns arise from drug
stability in the liquid state and leakage when nebuliz-
ers are used to deliver a liposomal encapsulated agent.111
Recently, liposomal dry powder formulations have been
intensively examined in order to successfully circumvent
these issues.72,112–114 Liposomal dry powder formulations have
been shown to be very promising in the delivery of various
types of pulmonary drugs and some of these formulations
are currently in clinical trials.
Much interest has focused on cationic liposomes for
pulmonary gene delivery because cationic liposomes offer
the advantage of self-assembly with DNA material through
favorable cationic–anionic electrostatic interactions.
Additional advantages include evasion from complement
Table 1 (Continued)
Therapeutic areas and drugs Drug typesaColloidal carrier self-assembly
systems and referencesb
Parathyroid disease
Elcatonin P PN65
Diabetes
Insulin P PN,66 LP,67,68 SLN69
Thrombosis
Low molecular weight heparin P DD70,71
Urokinase P PN72
Notes: aS, small molecules; P, protein/peptide; G, gene; bDN, drug nanoparticle; PN, polymeric nanoparticle; LP, liposome; SLP, solid lipid nanoparticle; DD, dendrimer;
SE, submicron emulsion; cCan be used for treatment of pulmonary hypertension as well as asthma.

International Journal of Nanomedicine 2009:4 303
Nanomedicine in pulmonary delivery
Dovepress
submit your manuscript | www.dovepress.com
Dovepress
inactivation after in vivo administration, the low cost and
relative ease in producing nucleic acid–liposome com-
plexes in large scale.95 After first report of inhalation gene
delivery success,115 many reports have been published
on gene delivery using cationic liposomes by pulmonary
administration.104,116–123 Many recent reviews95,124,125 present
gene delivery system using cationic liposomes. Moreover,
liposomes conjugated with cell-penetrating peptides are
recognized as potential nanocarrier systems for intracel-
lular delivery of macromolecules to the lung. Liposomes
modified with cell-penetrating peptides, antennapedia,
the HIV-1 transcriptional activator, and octaarginine have
been reported to enhance the cellular uptake of liposomes
to airway cells.126
Solid lipid nanoparticles in pulmonary
delivery
Solid lipid nanoparticles (SLNs) are made from solid
lipids (ie, lipids solid at room temperature), surfactant(s)
and water.127 Since the beginning of 1990s, the SLNs have
been focused on an alternative to polymeric nanopar-
ticles.109 The advantages of drug release from SLNs in the
OH
OH
OH
OH
HO
HO
H
NH
NN
N
N
N
NN N
Itraconazole
Budesonide
N
H
OO
O
N
N
N
Cl
Cl
NN
N
N
N
N
N
N
N
N
H
HH
H
H
H
H
H
H
H
H
H
H
H
Cyclosporine A
O
O
O
H3C
CH3
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
NaOOC
O
H
Low molecular weight heparin (Enoxaparin) Vasoactive intestinal peptide
Insulin
O
O
O
O
O
O
O
O
n
His
Gly
lle
Val
Glu Gln Cys
Cys
Cys Thr Ser
Ser
lle Cys Ser Leu
Leu Leu Leu Val Cys Gly
Tyr
Tyr
Gln
Glu
Glu
Glu
Arg
Gly
Phe
Phe
Tyr
Pro
Thr Thr
Asn Tyr Cys Asn
Asn
Phe
Val
Gln His Gly His Leu
Lys
Val Ala
Leu
Ser Asp Val Phe Asp Asn
Asn
Ala
Asn
Tyr Thr
Thr
Ser
lle Tyr
Arg Leu
LeuLeu
Arg
Gln
Met
Ala
Val
Lys
Lys
Lys
n
3or 10
or
or or
O
S
S
S
S
S
S
CH3
C
O
OR
RR2
CH2OR
NHR2
SO3Na SO3Na
NHR2
OH
OSO3Na
OH OH OH
OH
OH
COOH
COONa CH2OR
O
H
HH
H
O
HO
HO
Rifampicin
O
Figure 1 Examples of drugs for pulmonary colloidal carriers (nanocarrier systems).

International Journal of Nanomedicine 2009:4
304
Mansour et al Dovepress
submit your manuscript | www.dovepress.com
Dovepress
lung are control of the release profile, achievement of a
prolonged release and having a faster in vivo degradation
compared to particles made from PLA or PLGA. In addi-
tion, SLNs proved to possess a higher tolerability in the
lungs compared to particles made from some polymeric
materials.109 ,128 ,12 9 Although SLNs for the pulmonary
delivery is not fully appreciated, toxicological profile of
SLNs, when using physiological lipids, is expected to be
better than that of polymer-based systems, because physi-
ological lipids have little or no cytotoxicicity.130,131 It is
feasible that aqueous suspensions and perhaps dry powder
formulations of SLN can be used for pulmonary inhalation
Table 2 Various polymers for colloidal pulmonary drug delivery systems
Polymers Drugs and references Size
Alginate
Sodium alginate Rifampicin, isoniazid, pyrazinamide29 235.5 nm
Chitosan
Chitosan Plasmid DNA77 91–164 nm
Small interfering RNA78 40–600 nm
Chitosan/tripolyphosphate Insulin79 300–388 nm
Trisaccharide-substituted chitosan Plasmid DNA80 77–90 nm
Urocanic acid–modied chitosan Programmed cell death protein 450 NA
Gelatin
Gelatin type A Fuoresceinamine81 277.8 nm
Gelatin type B Sulforhodamine 101 acid chloride82 242 ± 14 nm
PEGylated gelatin Plasmid DNA83 100–500 nm
Polyalkylcyanoacrylate
Polybutylcyanoacrylate Insulin66 254.7 nm
Doxorubicin84 173 ± 43 nm
Ciprooxacin85 156–259 nm
PLGA
PLGA Rifampicin, isoniazid, pyrazinamide28 570–680 nm
PEG-PLGA Nuclear factor κB decoy oligodeoxynucleotide17 44 nm
Chitosan-modied PLGA Elcatonin65 650 nm
Chitosan/PLGA Antisense oligonucleotide 2-O-methyl-RNA51 135–175 nm
Poly[vinyl 3-(diethylamino)propylcarbamate-co-vinyl
acetate-covinyl alcohol]-graft-PLGA
5(6)-carboxyuorescein86 195.3 ± 7.1 nm
Proticle
Protamine-oligonucleotide Vasoactive intestinal peptide14 177–318 nm
PEI
PEI Chimeric oligonucleotide55 30–100 nm
Plasmid DNA87 50–100 nm
PEI-alt-PEG Small interfering RNA53 NA
Glucosylated PEI Programmed cell death protein 449 NA
Galactose-PEG-PEI Plasmid DNA88 105–210 nm
Cell-penetrating peptides-PEG-PEI Plasmid DNA89 113–296 nm
Poly-L-lysine
PEGylated poly-l-lysine Plasmid DNA90,91 211 ± 29 nm
Dendrimer
G9 PAMAM Plasmid DNA92 NA
G2/G3 PAMAM Low molecular weight heparin70 NA
Pegylated G3 PAMAM Low molecular weight heparin71 17.1 ± 3.3 nm
Abbreviations: PEG, poly(ethylene glycol); PLGA, poly(lactic-co-glycolic acid); PEI, poly(ethylenimine); PAMAM, polyamidoamine; NA, not available.

International Journal of Nanomedicine 2009:4 305
Nanomedicine in pulmonary delivery
Dovepress
submit your manuscript | www.dovepress.com
Dovepress
aerosol administration of drugs using nebulizers and dry
powder inhalers.109
Several studies have been published on the pulmonary
applications of SLNs as local delivery carriers for
small molecules42 or as systemic delivery carriers for
macromolecules.73,132 Pandey and Khuller42 studied the
chemotherapeutic potential of SLNs incorporating rifam-
picin, isoniazid and pyrazinamide against experimental
tuberculosis, and observed the slow and sustained-release
of drugs from the SLNs in vitro and in vivo. Gene delivery
Figure 2 Chemical structures of polymers for polymeric nanoparticles in pulmonary delivery systems.
Poly(lactide-co-glycolide) Chitosan Polybutylcyanoacrylate
Linear polyethyleneimine Branched polyethyleneimine
Poly-L-lysine
-[Ala-Gly-Pro-Arg-Gly-Glu-4Hyp-Gly-Pro]n−
Gelatin G3 Dendrimer
HO
O
O
O
O
O
O
O
O
O
OO
O
O
O
O
O
O
O
O
O
O
O
O
O
0.5
1
1.5
2
2.5
3
O
O
OO
O
O
O
O
O
O
O
O
O
O
O
O
OH
O
O
O
OO
O
O
O
O
O
H
HH
H
H
OH
CN
CH2OH
CH3
NH2
NH2NH2
H2N
H2N
HN
HN HN
HN
NH
NH
NH
NH
NH NH
N
N
N
N
N
NH
NH
HN
NH
NH
NH
NH
NH
NH
NH
NH
NH
NH
NH
NH
NH
NH
NH
NH
NH
NH
NH
NH
NH
NH
NH
NH
HN
HN
HN
HN
N
N
NN
N
N
N
N
N
N
N
NN
N
NH
NH
NH
N
N
N
NH
NN
N
NH2
H2N
H2N
H2N
H2N
H2N
H2N
H2N
NH2
NH2
NH2
NH2
NH2
NH2
NH2
NH2
H2N
H2N
+
-
NH2
NH2
NH2
NH2
N
H3C
n
n
n
n
n
y
x

International Journal of Nanomedicine 2009:4
306
Mansour et al Dovepress
submit your manuscript | www.dovepress.com
Dovepress
of SLN-based gene vectors was introduced by Rudolph and
colleagues.132 They reported that SLN gene vectors mediate
gene expression in the mouse lungs upon aerosol application,
which was increased by the TAT peptide, and aerosol
application of fragile gene delivery systems can be achieved
by a mild nebulization technology based on a novel perforated
membrane technology. Liu and colleagues73 studied novel
nebulizer-compatible SLNs containing insulin for pulmonary
delivery. They concluded that SLNs could be successfully
applied as a pulmonary carrier system for insulin, which
might provide novel solutions to the currently unmet medical
needs for systemic delivery of proteins.
Deposition and clearance of SLNs were assessed by
Videira and colleagues133,134 after inhalation of aerosolized
insoluble particles using gamma-scintigraphy imaging
analysis. It was observed that a few minutes after deposi-
tion, inhaled material began to translocate to regional lymph
nodes indicating that inhalation can be an effective route
to deliver drug-containing lipid partices to the lymphatic
systems and lipid particles can be used as potential drug
carriers for lung cancer therapy, as well as for vaccine
delivery.133,134
Submicron emulsions in pulmonary
delivery
Until now, the submicron emulsion system has not yet
been fully exploited for pulmonary drug delivery and very
little has been published in this area.65 Cationic submicron
emulsion loaded with Mycobacterium tuberculosis Ag85B
DNA vaccine was explored vaccine for the purpose of
pulmonary mucosal vaccination.65 Emulsion systems
have been introduced as alternative gene transfer vectors
to liposomes.135 Other emulsion studies for gene delivery
(nonpulmonary route) have shown that binding of the
emulsion/DNA complex was stronger than liposomal
carriers.136 This stable emulsion system delivered genes to
endothelial cells in the mouse nasal cavity more efficiently
than commercially available liposomes.137 Bivas-Benita
and colleagues65 have reported that cationic submicron
emulsions are promising carriers for DNA vaccines
to the lung since they are able to transfect pulmonary
epithelial cells, which possibly induce cross priming of
antigen-presenting cells and directly activate dendritic
cells, resulting in stimulation of antigen-specific T-cells.
Therefore the nebulization of submicron emulsions will
be a new and upcoming research area. However, exten-
sive studies are required for the successful formulation of
inhalable submicron emulsions due to possible adverse
effects of surfactants and oils on lung alveoli function
(adverse interactions with lung surfactant).
Dendrimer-based nanoparticles for lung
delivery
Dendrimers are polymers, which have hyperbranched
structures, with layered architectures.138 The research in
dendrimer-mediated drug delivery has mainly been focused
on the delivery of DNA drugs into the cell nucleus for gene
or antisense therapy, and many studies have been reported
on the possible use of dendrimers as nonviral gene transfer
agents.138 Several studies have been published regarding
pulmonary applications of dendrimers as systemic delivery
carriers for macromolecules.74,75,93,139
Kukowska-Latallo and colleagues93 investigated the
ability of polyamido amine (PAMAM) dendritic polymers
(dendrimers) to augment plasmid DNA gene transfer in vivo
and evaluates the targeting of the lung by alternative routes
of administration. They suggested that vascular administra-
tion seemed to achieve expression in the lung parenchyma,
mainly within the alveoli, while endobronchial administration
primarily targeted bronchial epithelium, indicating that each
delivery route requires different vectors to achieve optimal
transgene expression, that each approach appears to target
different cells within the lung.
Rudolph and colleagues139 compared the properties of
branched polyethylenimine (PEI) 25 kDa and fractured
PAMAM dendrimers for topical gene transfer to the air-
ways in vivo. Their results demonstrated that gene transfer
mediated by PEI under optimal conditions was two orders
of magnitude higher compared to fractured dendrimers.
Therefore, branched PEI 25 kDa was superior to fractured
dendrimers for gene delivery to the airways.
Bai and colleagues74 produced low molecular weight
heparin (LMWH)–dendrimer complex through electrostatic
interactions using various PAMAM dendrimers, then evalu-
ated both the safety and the efficacy of the drug–dendrimer
formulations in preventing deep vein thrombosis in vivo
and in situ. They concluded that cationic dendrimers can
be used as pulmonary delivery carriers for a relatively large
molecular weight anionic drug. These carriers bind anionic
drug molecules most likely via electrostatic interactions and
increase drug absorption through charge neutralization. In
addition, preliminary safety studies using the frog palate
model and bronchoalveolar lavage analysis suggest that
dendrimers could be viable carriers for pulmonary delivery
of LMWH. In another study the same group75 also inves-
tigated pegylated dendrimers (mPEG–dendrimer) in order

International Journal of Nanomedicine 2009:4 307
Nanomedicine in pulmonary delivery
Dovepress
submit your manuscript | www.dovepress.com
Dovepress
to increase pulmonary absorption and circulation time
of the drug. Briefly, half-life and absorption of LMWH
administered via the pulmonary route can be increased by
encapsulating the drug in dendrimeric micelles, and their
study suggests that LMWH loaded in the mPEG–dendrimer
could potentially be used as noninvasive delivery system
for the treatment of thromboembolic disorder. However, the
potential of dendrimers in the pulmonary drug administration
route still remains as a challenge that needs further research
to achieve lower cytotoxicity and higher biocompatibility.
Manufacture of nanoparticulate
inhalation aerosols
In formulation preparation, several processing technologies
have been used to obtain nanoparticles for use as pulmonary
inhalation aerosols with desirable attributes, such as narrow
particle size distribution, enhanced stability, controlled and
targeted release, and improved bioavailability. Jet-milling of
the drug under nitrogen gas is the traditional way of creating
respirable aerosol particles in the solid-state.140,141 The basic
procedure of jet-milling is to grind a bulk crystallized par-
ticles into small particles by one of the following mechanical
forces: pressure, friction, attrition, impact, or shear. However,
up until very recently, this technology had a limitation to
generate particles in the nanosized range, although a few
cases have been reported to produce nanoparticles, such as
insulin nanoparticles142 and budesonide nanoparticles,143 by
wet milling process. The recent availability of new nanojet
milling instruments which produce nanoparticles by jet
milling may increase the routine use of creating nanoparticles
by this method.
More sophisticated and advanced manufacturing
technologies are utilized to produce respirable aerosol
nanoparticles. These respirable particles may be encapsu-
lated in microparticles in the respirable aerodynamice size
range of 1–5 microns or the nanoparticles may be designed
to aggregate to a favorable aerodynamic size range. These
manufacturing nanotechnologies include spray drying (some-
times referred to as advanced spray drying or nanospray
drying), spray-freeze drying, supercritical fluid technology,
double emulsion/solvent evaporation technology, antisolvent
precipitation, particle replication in nonwetting templates
(PRINT), and thermal condensation using capillary aerosol
generator.
Spray-drying
Spray-drying is an advanced pharmaceutical manufacturing
process used to efficiently produce respirable colloidal
particles in the solid-state.144,145 In the process, the feed
solution is supplied at room temperature and pumped to the
nozzle where it is atomized by the nozzle gas. The atomized
solution is then dried by preheated drying gas in a special
chamber to remove water moisture from the system, thus
forming dry particles. These prepared particles are collected
with a cyclone separation device. A schematic representation
of a spray drying process is shown in Figure 3.
The spray-drying process is suitable for thermolabile
materials such as proteins and peptides, because mechanical
high energy input is avoided in this process.146–148 Moreover,
the spray-drying system can be modified to meet specific
needs. For example, Maa and colleagues149 replaced the
bag-filter unit of a spray-drying system with a vacuum to
reduce the drying airflow resistance. It allows the protein
(recombinant humanized anti-lgE antibody) to be dried at a
much lower temperature than usual and the production scale
to be increased.146 In another study, poly(lactic-co-glycolic
acid) particles containing proteins were successfully dried by
ultrasonic atomization of feed solution into an atmosphere
under reduced pressure.147 Solution spray-drying ensures
compositional homogeneity of the drug powder, since the
drug and the excipients are dissolved prior to the process.
More importantly, spray-drying can result in uniform particle
morphology.114,149,150 In industry, spray-drying is a continu-
ous production method, scalable for commercial production
volumes.
Lactose monohydrate is the only US Food and Drug
Administration (FDA)-approved sugar carrier for dry pow-
der aerosol formulations and one of a few FDA approved
excipients.151 For example, lactose with either gelatin or
poly(butylcyanoacrylate) nanoparticles were spray dried to
produce particles for pulmonary delivery.84 Lactose in solid
form can be either crystalline as lactose monohydrate or
amorphous as lactose. Crystalline lactose can exist in one of
two distinct forms: α-lactose monohydrate (Figure 4a) and
anhydrous β-lactose (Figure 4b). Amorphous lactose may
contain both α- and β-lactose molecules that are arranged
in a more or less random state. α-lactose monohydrate and
anhydrous β-lactose are superior in offering better physical
stability than amorphous lactose as the later has a tendency
to recrystallize spontaneously.152,153 A disadvantage of lactose
monohydrate, a reducing sugar, as a sugar carrier and/or
excipient in the solid-state is that it participates in Maillard
decomposition reactions with certain small molecular weight
pulmonary drugs (eg, budesonide, formoterol), proteins
and peptides.154 Recently, D-mannitol, a nonreducing sugar
alcohol, whose molecular structure is shown in Figure 4c, has

International Journal of Nanomedicine 2009:4
308
Mansour et al Dovepress
submit your manuscript | www.dovepress.com
Dovepress
been used as an alternative sugar carrier of pulmonary drugs
in dry powder inhalation aerosols, since it does not participate
in the solid-state decomposition Maillard reaction.155
Spray-freeze-drying (SFD)
Spray-freeze-drying (SFD) is an advanced particle
engineering method which combines spray-drying and
freeze-drying processing steps. This technique involves
the atomization of an aqueous drug solution into a spray
chamber filled with a cryogenic liquid (liquid nitrogen)
or halocarbon refrigerant such as chlorofluorocarbon or
fluorocarbon.156 The water is removed by sublimation after
the liquid droplets solidify.157 SFD is capable of producing
porous particles with high fine particle fraction (FPF) at
subambient temperatures.157 They are usually low-density
composite amorphous particles with high specific surface
area.158 Thermolabile protein and peptide substances, such
as insulin159 and plasmid DNA,160 can also be formulated into
dry powder inhalation products by SFD.
Supercritical uid technology (SCF)
The basic feature of the supercritical fluid process is the
controlled crystallization of drugs from dispersion in super-
critical fluids, carbon dioxide. This method has demon-
strated a wide range of application in producing pulmonary
inhalable formulations.23,161,162 Supercritical fluid technology
can be divided into several classes. The most important two
are supercritical antisolvent precipitation (SAS)163,164 and
supercritical fluid extraction of emulsions (SFEE).165,166
The fundamental mechanism of SAS is based on rapid
precipitation when a drug solution is brought into contact
with a supercritical CO2. SFEE is based on extraction of
the organic phase in oil-in-water or multiple emulsions
using supercritical CO2.165,166 The schematic representation
of SAS and SFEE processes is shown in Figure 5. Because
most of the drugs (eg, asthma drugs) are not soluble in
CO2, SAS processes provide an easy and excellent way
to produce dry powder inhalation formulations.163,164
SFEE can provide uniform crystalline drug nanoparticles,
composite nanoparticles containing polymeric materials
and the drugs, and nanosuspensions.165,166 For instance,
Chattopadhyay and colleagues23 used a continuous SFEE
method to produce nanoparticle suspensions containing one
of three lipids (tripalmitin, tristearin, or gelucire 50/13),
and one of two model drugs (indomethacin or ketoprofen).
The first step of this process was to produce nanoemulsions
by mixing organic phase containing lipids, a selected drug
and chloroform with aqueous phase containing sodium gly-
cocholate, under high pressure homogenization. Then the
nanoemulsions were introduced to an extraction chamber
countercurrently to a stream of supercritical CO2. The CO2
extracted the organic solvent from the dispersed droplets,
Figure 3 A schematic representation of the spray-drying process.
feed solution
drying
champer
cyclone
separation
particle
collection
pump
nozzle gas
nozzle
drying gas
exhaust gas

International Journal of Nanomedicine 2009:4 309
Nanomedicine in pulmonary delivery
Dovepress
submit your manuscript | www.dovepress.com
Dovepress
forming nanoparticles with a volume mean diameter
between 10–30 nm with a high drug loading efficiency for
the gelucire particles (∼80%–90%). In another example,
nanoparticles containing cholesterol acetate (CA), griseo-
fulvin (GF), and megestrol acetate (MA) were produced by
extraction of the internal phase of oil-in-water emulsions
using supercritical carbon dioxide.165 This method offered
advantages such as the control of particle size, crystallinity,
and surface properties. Meanwhile, it shortened the pro-
cessing time, improved the product purity, and reduced the
large waste streams.
Double emulsion/solvent evaporation
technique
Respiratory nanoparticle formation from double emulsion/
solvent evaporation system involves preparation of oil/water
(o/w) emulsions with subsequent removal of the oil phase
(ie, typically a volatile organic solvent) through evapora-
tion. The emulsions are usually prepared by emulsifying
the organic phase containing the drug, polymer and organic
solvent in an aqueous solution containing emulsifier. The
organic solvent diffuses out of the polymer phase and into the
aqueous phase, and is then evaporated, forming drug-loaded
polymeric nanoparticles. By this method, biodegradable
polymers, including poly(l-lactic acid) (PLA), poly(glycolic)
acid (PGA), and poly(lactide-co-glycolide) acid (PLGA),
have been intensively investigated as carriers for solid drug
nanoparticles.167
Antisolvent precipitation
Crystalline drug particles with narrow size distribution
could be prepared by direct controlled crystallization.168 This
process involves antisolvent precipitation of drug solution in
a water-miscible organic solvent, followed by addition of a
bridging solvent, which is immiscible or partially miscible
with water. Growth-retarding stabilizing additives, such as
hydroxylpropylmethylcellulose (HPMC), is usually added in
the medium to yield particles with small size. The precipi-
tated drug crystals exhibit a high FPF and low amorphous
content.169
Particle replication in nonwetting
templates (PRINT)
PRINT is a top-down particle fabrication technique devel-
oped by Dr. Joseph DeSimone and his group. This tech-
nique is able to generate uniform populations of organic
micro- and nanoparticles with complete control of size,
shape and surface functionality, and permits the loading
of delicate cargos such as small organic therapeutics, pep-
tides, proteins, oligonucleotides, siRNA, contrast agents,
radiotracers, and fluorophores.170–172 All these features are
essential for controlling in vivo transport, biodistribution,
Figure 4 Molecular structures of sugar carriers: A) α-lactose monohydrate, B) anhydrous β-lactose and C) D-mannitol.
O
OH
OH
OH
HO
O
O
OH
OH
OH
HO
.H2O
A) B)
C)
O
OH
OH
OH
HO
O
O
OH
OH
HO
OH
HO
OH
OH
OH
OH
OH

International Journal of Nanomedicine 2009:4
310
Mansour et al Dovepress
submit your manuscript | www.dovepress.com
Dovepress
and drug-release mechanisms of nanoparticles. The principle
of PRINT is to utilize a low surface energy fluoropolymeric
mold that enables high-resolution imprint lithography, an
emerging technique from the microelectronics industry, to
fabricate a variety of organic particles. PRINT is therefore
an adaptation of lithographic techniques found in the micro-
electronics industry to fabricate carriers of precise size for
use in nanomedicine. Through the use of an appropriately
designed master template, PRINT can precisely manipulate
particle size ranging from 20 nm to more than 100 µm. The
shape of particles can be sphere, cylinder, discs, and toroid
with defined aspect ratios. PRINT is a promising and novel
technology in nanoparticulate design and manufacture for
use in pulmonary delivery.
Thermal condensation aerosols
Thermal condensation is a cutting edge technology which
uses capillary aerosol generator (CAG) to produce high
concentration condensation submicron to micron sized
aerosols from drug solutions. The drug solution is pumped
through a heated capillary tube. Precisely controlled heating
of the capillary causes the solution to evaporate. Formula-
tion vapor exiting the tip of the capillary tube mixes with the
cooler surrounding air, and then becomes supersaturated and
initiates nucleation. The condensation of surrounding vapor
onto the generated nuclei results in an aerosol. Various drugs,
such as perphenazine,173 prochlorperazine,174 rizatriptan175
and benzyl,176 have been aerosolized using this technique.
Propylene glycol (PG) is a popular solvent chosen to dissolve
the drugs.177 However, in some cases, rapid heating of thin
films of pharmaceutical compounds can also vaporize the
molecules, leading to formation of aerosol particles of
optimal size for pulmonary drug delivery.178 By controlling
the film thickness, the purity of aerosols can be enhanced by
reducing the amount of aerosol decomposition.179
In vitro evaluation methods
for pulmonary drug delivery systems
In vitro characterization of
nanoparticulate aerosol systems
Nanoparticles for pulmonary drug delivery can be evaluated
by comprehensive characterization methods. Table 3 lists
several important techniques as well as their functions in the
in vitro characterization study of the behavior of nanopar-
ticulate pulmonary inhalation aerosols.180
Inertial impaction is the standard method to measure the
particle or droplet aerodynamic size from pharmaceutical
aerosol delivery systems.181,182 It describes the phenomenon
of the deposition of aerosol particles on the walls of an airway
conduct. The impaction (obstruction) tends to occur where
the airway direction changes. The big particles have high
momentum (inertia) and are more likely to travel in the initial
direction of airflow, while those with low momentum adjust
to the new direction of flow and pass around the obstruction.
Inertial impaction employs Stokes’ law to determine the
aerodynamic diameter of particles being evaluated. This has
the advantage of incorporating shape and density effects into
a single term.141
In addition to the conventional commercially avail-
able cascade impactors, MSP Corporation (Minneapolis,
MN, USA) has recently developed a new commercially
available nanomicroorifice uniform deposition impactor
(Nano-MOUDI™) device with high accuracy in sampling
and collecting size-fractionated airborne particle samples
and pharmaceutical aerosol particle samples for gravimetric
and/or chemical analysis. The Nano-MOUDI™ differs from
conventional cascade impactors by using microorifice nozzles
to reduce the jet velocity, pressure drop, particle bounce, and
evaporative loss. These impactors also have a uniform deposit
feature by rotating the impaction plates with respect to the
Table 3 Methods to characterize the physicochemical and aerodynamic properties of particles (microparticles and nanoparticles) for
pulmonary inhalation delivery
Technology Function
Inertial impaction Measurement of the aerodynamic size of particles
XRPD Measurement of molecular long-range vs short-range order
DSC Measurement the phase transitions and phase behavior
SEM Visualization of the surface morphology of particles
AFM Surface nanotopographical imaging, surface free energy measurements, and measure of interparticulate forces
IGC Determination of the surface free energy of bulk powders
Karl Fisher titration Analytical quantication of water content in pharmaceutical powders, liquids, and semi-solids
Abbreviations: AFM, atomic force microscopy; DSC, differential scanning calorimetry; IGC, indocyanine green; SEM, scanning electron microscopy; XRPD, X-ray particle
diffraction.

International Journal of Nanomedicine 2009:4 311
Nanomedicine in pulmonary delivery
Dovepress
submit your manuscript | www.dovepress.com
Dovepress
nozzles to spread out the particle deposit uniformly on the
collection substrates. The uniform deposit prevents heavy
particles build-up under each nozzle to reduce particle bounce
and blow-off that may otherwise occur. Nano-MOUDI™ is
also superior to conventional cascade impactors in its aero-
dynamic design features. It is designed to prevent cross-flow
interference between adjacent nozzles, which results in sharp
cut-size characteristics not available with other cascade
impactors. Because of its superior aerodynamic design and
outstanding performance characteristics, Nano-MOUDI™
has an increasing application in environmental air quality
and air pollution studies.183–190 We believe its application in
pharmaceutical nanoaerosol drug delivery characterization
and modeling is very promising, as well.
X-ray powder diffraction (XRPD) is one of the most
important characterization tools used in solid state chem-
istry and materials science, since it directly measures
the degree of molecular long-range vs short-range order.
Molecular long-range order is indicative of crystallinity,
while short-range order is indicative of noncrystallinity such
as liquid crystallinity and amorphicity. It gives information
about the extent and nature of crystallinity and molecular
order for solid-state materials, ie, how the atoms pack
together in the crystalline state and what the interatomic
distance and angle are.191–194
Differential scanning calorimetry (DSC) is a powerful
and routinely used pharmaceutical thermal analytical method
for phase behavior study on polymorphs, hydrates, binding
interactions, amorphocity, thermotropic and lyotropic phase
transitions of pharmaceutical materials, including nanopar-
ticles. DSC directly measures the gain and loss of enthalpy,
that is, order-to-disorder (eg, melting) and disorder-to-order
(eg, crystallization) phase transitions.195
Scanning electron microscopy (SEM) is used to visualize
the surface morphology of particles with a high magnifica-
tion. The resolution allows identification of specific surface
features and asperities that lead to mechanical interlocking
(ie, structural cohesion) and that contain high-energy “active”
Figure 5 Schematic representations of A) SAS and B) SFEE processes.
CO2 supply
cylinder
precipitation
chamber
nozzle
pump
drug solution
back pressure regulator
A)
B)
CO2 supply
cylinder
extraction
chamber
nozzle
pump
oil-in-water or
multiple emulsions
back pressure regulator

International Journal of Nanomedicine 2009:4
312
Mansour et al Dovepress
submit your manuscript | www.dovepress.com
Dovepress
sites on the surface which influence surface energetic
properties and interparticulate interactions and ultimately
influence aerosol dispersion performance.180 Surface and
interfacial/interparticulate forces are of great importance
in the properties of nanoparticles and in the properties of
aerosols. Atomic force microscopy (AFM) is used in surface
nanotopographical imaging, measurement of surface energy,
and measurement of interparticulate forces. This microscopy
works in mesoscopic scale resolution (10-6–10-9 m).196
Inverse gas chromatography (IGC) measures the surface
free energy of bulk powders such as polymers, fibers, and
composite materials.197
Karl Fischer titration is used to analytically quantify
small amounts of water present in the inhalation powder
which has important consequences on capillary condensa-
tion (ie, capillary force is an important interparticulate force
in inhalation aerosol particles), solid-state phase behavior,
solid-state properties, and solid-state stability of pharmaceuti-
cal particles in the solid-state.198
In vitro pulmonary cell culture models
The lung can be anatomically divided into several parts:
the trachea, the main bronchi, the conducting bronchioles,
the terminal bronchioles and the alveoli.199,200 Drug delivery
via inhalation may be absorbed throughout the conducting
airway from the trachea down to the terminal bronchioles
and ultimately the distal alveoli.201 The airway and alveolar
epithelium of the lung, which have different cell types,
provide barrier capability to drug absorption.
In order to better understand the drug absorption process
in different regions (eg, tracheal, bronchial and alveolar) of
the respirable barriers, in vitro pulmonary cell culture models
have been developed.201–205 The cell lines used include A427,
A549, HBE14o, and the Calu line (-1, -2, and -3).205–210 These
are immortal (continuous) cell lines and hence have different
membrane structural features compared with mortal cell lines
which influence drug absorption and efflux. For example,
A549 cell line represents the alveolar type II pulmonary
epithelial cell, and has been reported to be an ideal model
to study the metabolic and macromolecule mechanisms of
drug delivery at the alveolar pulmonary epithelium because
the endocytic ability of the pulmonary epithelium and local-
ization of cytochrome P450 systems is largely a function
of type II pneumocytes.209 Calu-3 and HBE14o model the
upper airways (bronchi) and many studies have been con-
ducted on them. For example, the permeability data of small
lipophilic molecule (eg, testosterone) and high molecular
weight substance (eg, fluorescein isothiocyanate-transferrin)
across Calu-3 cell line has been examined by Foster and
colleagues.208 The authors demonstrated this cell line is
useful for studying the contributions of bronchial epithelial
cells to the mechanisms of drug delivery at the respiratory
epithelium. Similar conclusions were drawn when the appar-
ent permeability of the glucocorticosteroid budesonide was
investigated.206
Primary cultured cells have also been used in pulmonary
absorption and transport studies. These cell cultures have
advantages over continuous cells by exhibiting tight junc-
tions. It is important for cell cultures to form a sufficient and
appropriately tight polarized monolayer, so that the transport
kinetics of test molecules can be properly assessed.211
In vivo evaluation methods
for pulmonary drug delivery systems
Pharmacokinetic study after nebulization
of colloidal dispersion of drugs
Colloidal drug dispersions have been delivered to male ICR
mice via nebulization using a restraint-free small animal
inhalation dosing chamber. Then, the mice were sacrificed at
pre-determined time points post-dosing. Blood samples were
taken by cardiac puncture, and the lungs were harvested for
analysis by analytical instrument. From these experiments,
lung and serum (blood) pharmacokinetics of colloidal drug
dispersions can be determined as reported previously.212–214
Biodistribution study using radiolabeled
SLNs
To assess the inhaled radiolabelled SLNs biodistribution,
nanoparticles (200 nm) were radiolabeled with 99mTc and
biodistribution studies were carried out following aerosolisa-
tion and administration of a 99mTc-HMPAO-SLNs suspension
to a group of adult male Wistar rats. After administration
of radiolabeled SLNs, dynamic image acquisition was
performed in a gamma-camera, followed by static image
collection. Then radiation counting was performed in organ
samples, collected after the animals were sacrificed. From
these experiments, biodistribution of SLNs can be traced
and evaluated.133,134
Fluorescence/bioluminescence imaging
systems for pulmonary gene delivery
Visualization and evaluation of both the pulmonary delivery
and the gene expression properties after dry powder
inhalation in mice were recently reported by Mizuno and
colleagues.215 It was shown that the pulmonary delivery and

International Journal of Nanomedicine 2009:4 313
Nanomedicine in pulmonary delivery
Dovepress
submit your manuscript | www.dovepress.com
Dovepress
the gene expression can be evaluated using fluorescence
of indocyanine green (ICG) as a fluorescent label and the
detection of luciferase activity, respectively, by using a non-
destructive real-time in vivo imaging system. They concluded
that the dry powder containing both ICG and pCMV-Luc
was useful as a dual imaging system to visualize pulmonary
delivery and gene expression in mice.
Regulatory and toxicity issues
Inhaled microparticles and nanoparticles of different sizes
can target into different regions of respiratory tract, including
nasopharyngeal, tracheal, bronchial, and alveolar regions,
with several mechanisms. Meanwhile, the surface chemistry,
charge, shape and aggregation status of nanoparticles
also have influences on their disposition efficacy.216 For
example, inhaled large particles and nanoparticles deposit
in the respiratory tract by distinctive mechanisms. Large
particles deposit via inertial impaction, gravitation settling
and interception mechanisms, while nanoparticles deposits
via diffusion due to displacement when they collide with air
molecules. The presence of albumin217 and phospholipids
(eg, lecithin)218 in alveolar epithelial lining fluid is important
to facilitate epithelial cell uptake of nanoparticles after
deposition in the alveolar space. Nanoparticles coated
with them may translocate across the alveolo–capilliary
barrier, whereas uncoated particles do not. Therefore,
when evaluating the efficacy and fate of nanoparticles by
inhalation delivery, all the variables should be taken into
consideration.1
After delivery into the lung, some nanoparticles may be
translocated to extrapulmonary sites and reach other target
organs by cellular endocytosis, transcytosis, neuronal,219
epithelial220 and circulatory221 translocation and distribu-
tion, which makes them desirable for medical therapeutic
or diagnostic application. However, these features can also
pose potential toxicity. Transcytosis absorbs nanoparticles
and translocate them into the interstitial sites, where they
gain access to the blood circulation via lymphatics, resulting
in distribution throughout the body. Neuronal translocation
involves uptake of nanoparticles by sensory nerve endings
embedded in airway epithelia, followed by axonal transloca-
tion to ganglionic and central nerve systems (CNS) structures.
For example, nanoparticles facilitating drug delivery to the
CNS in the brain raises the question of fate of nanopar-
ticles after their translocation to the specific cell types or
to subcellular structures. This kind of questions includes
whether mitochondrial localization induces oxidative stress
and how persistent the coating or the core of nanoparticles
is, which is essential in nanoparticle toxicology and safety
evaluation.222
The clearance of nanoparticles in the alveolar region is
predominantly mediated by alveolar macrophages, through
phagocytosis of deposited nanoparticles. After macrophages
recognize the deposited nanoparticles and phagocytize them,
macrophages with internalized nanoparticles gradually move
toward the mucociliary escalator, and then the clearance
process is started. The retention half-time of solid particles
in the alveolar region based on this mechanism is very
slow, up to 700 days in humans. Moreover, unlike larger
particles, results from several studies show the apparent inef-
ficiency of alveolar macrophage phagocytosis of nanosized
particles.223–225 The ultrafine nanoparticles are not easily
phagocytized by macrophages and, consequently, are not
readily cleared in the alveolar region.226 These nanoparticles
are either in epithelium cells or are further translocated to
the interstitium, which may cause a long-term accumulation
in the lung and subsequent toxicity issues.
According to the FDA guidance for dry powder inhaler
(DPI) drug products, α-lactose monohydrate is the only
approved sugar that can be used as a large carrier particle
in dry powder inhalation aerosol products to fluidize and
disperse the respiratory drug while itself not being delivered
to the lung. Other novel materials, including phospholipids,
specifically lecithin and amino acids (lysine, polylysine) have
also been developed for use in pulmonary formulations as
excipients that are delivered to the lung. A thorough assess-
ment of these alternatives associated with any inhalable
substance is required, from a variety of sources: human,
animal, and/or in vitro test models.227
Conclusions
Inhalable colloidal carriers (nanocarrier systems) offer
numerous advantages. The decrease in particle size leads
to an increase in surface area leading to enhanced dis-
solution rate, as well as relatively uniform distribution of
drug dose among the alveoli. In addition, by suspending
the drugs in nanoparticles, one can achieve a dose that is
higher than that offered by a pure aqueous solution, which
is thermodynamically limited by the aqueous solubility of
the drug. Nanocarrier systems can provide the advantage
of sustained-release in the lung tissue, resulting in reduced
dosing frequency and improved patient compliance. Local
delivery of inhalable nanocarriers may be a promising alter-
native to oral or intravenous administration, thus decreasing
the incidence of side effects associated with a high drug
serum concentration. As with all formulations designed for

International Journal of Nanomedicine 2009:4
314
Mansour et al Dovepress
submit your manuscript | www.dovepress.com
Dovepress
pulmonary drug delivery, the potential long-term risk of
excipient toxicity and nanoscale carrier itself are issues that
need to be considered in the successful product development
of pulmonary drug delivery systems. Nevertheless, their
inherently small size and surface modification properties
enable further opportunities for innovative controlled drug
release and pulmonary cell targeting therapeutic platforms.
The integration of nanotechnology and pulmonary delivery
has the potential to improve the targeting, release, and thera-
peutic effects of drugs and needle-free inhalation vaccines
with significant potential capability of overcoming the
physicochemical and biological hurdles.
Disclosure
The authors report no conflicts of interest in this work.
References
1. Yang W, Peters JI, Williams RO 3rd. Inhaled nanoparticles–a current
review. Int J Pharm. 2008;356:239–247.
2. Patton JS, Byron PR. Inhaling medicines: delivering drugs to the body
through the lungs. Nat Rev Drug Discov. 2007;6:67–74.
3. Sung JC, Pulliam BL, Edwards DA. Nanoparticles for drug delivery to
the lungs. Trends Biotechnol. 2007;25:563–570.
4. Bailey MM, Berkland CJ. Nanoparticle formulations in pulmonary drug
delivery. Med Res Rev. 2009;29:196–212.
5. Shekunov B. Nanoparticle techno logy for drug deliver y – From
nanoparticles to cutting-edge delivery strategies – Part I – 21–22 March
2005, Philadelphia, PA, USA. Idrugs. 2005;8:399–401.
6. Kreuter J. Nanoparticle-based drug delivery systems. J Control Release.
1991;16:169–176.
7. Brigger I, Dubernet C, Couvreur P. Nanoparticles in cancer therapy
and diagnosis. Adv Drug Deliv Rev. 2002;54:631–651.
8. Tiwari SB, Amiji MM. A review of nanocarrier-based CNS delivery
systems. Curr Drug Deliv. 2006;3:219–232.
9. Kaur IP, Bhandari R, Bhandari S, Kakkar V. Potential of solid
lipid nanoparticles in brain targeting. J Control Release. 2008;
127:97–109.
10. Driscoll D, Bhargava H, Li L, Zaim R, Babayan V, Bistrian B.
Physicochemical stability of total nutrient admixtures. Am J Health
Syst Pharm. 1995;52:623–634.
11. Koster VS, Kuks PFM, Lange R, Talsma H. Particle size in parenteral
fat emulsions, what are the true limitations? Int J Pharm. 1996;134:
235–238.
12. Zimmer A, Kreuter J. Microspheres and nanoparticles used in ocular
delivery systems. Adv Drug Deliv Rev. 1995;16:61–73.
13. Chono S, Tanino T, Seki T, Morimoto K. Influence of particle size
on drug delivery to rat alveolar macrophages following pulmonary
administration of ciprofloxacin incorporated into liposomes. J Drug
Target. 2006;14:557–566.
14. Park JH, Lee S, Kim JH, Park K, Kim K, Kwon IC. Polymeric
nanomedicine for cancer therapy. Prog Polym Sci. 2008;33:113–137.
15. Resnik DB, Tinkle SS. Ethical issues in clinical trials involving
nanomedicine. Contemp Clin Trials. 2007;28:433–441.
16. Azarmi S, Roa WH, Lobenberg R. Targeted delivery of nanopar-
ticles for the treatment of lung diseases. Adv Drug Deliv Rev.
2008;60:863–875.
17. Cryan SA. Carrier-based strategies for targeting protein and peptide
drugs to the lungs. AAPS J. 2005;7:E20–E41.
18. Joshi MR, Misra A. Liposomal budesonide for dry powder inhaler:
preparation and stabilization. AAPS Pharm Sci Tech. 2001;2:25.
19. Konduri KS, Nandedkar S, Duzgunes N, et al. Efficacy of liposomal
budesonide in experimental asthma. J Allergy Clin Immunol.
2003;111:321–327.
20. Stenton GR, Ulanova M, Dery RE, et al. Inhibition of allergic inflam-
mation in the airways using aerosolized antisense to Syk kinase.
J Immunol. 2002;169:1028–1036.
21. Joshi M, Misra A. Disposition kinetics of ketotifen from liposomal
dry powder for inhalation in rat lung. Clin Exp Pharmacol Physiol.
2003;30:153–156.
22. Seong JH, Lee KM, Kim ST, Jin SE, Kim CK. Polyethylenimine-
based antisense oligodeoxynucleotides of IL-4 suppress the produc-
tion of IL-4 in a murine model of airway inflammation. J Gene Med.
2006;8:314–323.
23. Chattopadhyay P, Shekunov BY, Yim D, Cipolla D, Boyd B, Farr S.
Production of solid lipid nanoparticle suspensions using supercritical
fluid extraction of emulsions (SFEE) for pulmonary delivery using the
AERx system. Adv Drug Deliv Rev. 2007;59:444–453.
24. Hajos F, Stark B, Hensler S, Prassl R, Mosgoeller W. Inhalable
liposomal formulation for vasoactive intestinal peptide. Int J Pharm.
2008;357:286–294.
25. Stark B, Debbage P, Andreae F, Mosgoeller W, Prassl R. Associa-
tion of vasoactive intestinal peptide with polymer-grafted liposomes:
structural aspects for pulmonary delivery. Biochim Biophys Acta.
2007;1768:705–714.
26. Wernig K, Griesbacher M, Andreae F, et al. Depot formulation of
vasoactive intestinal peptide by protamine-based biodegradable
nanoparticles. J Control Release. 2008;130:192–198.
27. Wijagkanalan W, Kawakami S, Takenaga M, Igarashi R, Yamashita F,
Hashida M. Efficient targeting to alveolar macrophages by intratracheal
administration of mannosylated liposomes in rats. J Control Release.
2008;125:121–130.
28. Gong F, Tang H, Lin Y, Gu W, Wang W, Kang M. Gene transfer
of vascular endothelial growth factor reduces bleomycin-induced
pulmonary hypertension in immature rabbits. Pediatr Int. 2005;47:
242–247.
29. Kimura S, Egashira K, Chen L, et al. Nanoparticle-mediated
delivery of nuclear factor {kappa}B decoy into lungs ameliorates
monocrotaline-induced pulmonary arterial hypertension. Hypertension.
2009.
30. Chougule MB, Padhi BK, Misra A. Nano-liposomal dry powder
inhaler of Amiloride Hydrochloride. J Nanosci Nanotechnol.
2006;6:3001–3009.
31. Gibbons AM, McElvaney NG, Taggart CC, Cryan SA. Delivery of
rSLPI in a liposomal carrier for inhalation provides protection against
cathepsin L degradation. J Microencapsul. 2008;1–10.
32. Beaulac C, Sachetelli S, Lagace J. Aerosolization of low phase transition
temperature liposomal tobramycin as a dry powder in an animal model
of chronic pulmonary infection caused by Pseudomonas aeruginosa.
J Drug Target. 1999;7:33–41.
33. Marier JF, Brazier JL, Lavigne J, Ducharme MP. Liposomal tobra-
mycin against pulmonary infections of Pseudomonas aeruginosa:
a pharmacokinetic and efficacy study following single and multiple
intratracheal administrations in rats. J Antimicrob Chemother. 2003;52:
247–252.
34. Labana S, Pandey R, Sharma S, Khuller GK. Chemotherapeutic
activity against murine tuberculosis of once weekly administered drugs
(isoniazid and rifampicin) encapsulated in liposomes. Int J Antimicrob
Agents. 2002;20:301–304.
35. Vyas SP, Kannan ME, Jain S, Mishra V, Singh P. Design of liposomal
aerosols for improved delivery of rifampicin to alveolar macrophages.
Int J Pharm. 2004;269:37–49.
36. Changsan N, Chan HK, Separovic F, Srichana T. Physicochemical
characterization and stability of rifampicin liposome dry powder for-
mulations for inhalation. J Pharm Sci. 2009;98:628–639.
37. Justo OR, Moraes AM. Incorporation of antibiotics in liposomes
designed for tuberculosis therapy by inhalation. Drug Deliv.
2003;10:201–207.

International Journal of Nanomedicine 2009:4 315
Nanomedicine in pulmonary delivery
Dovepress
submit your manuscript | www.dovepress.com
Dovepress
38. Pandey R, Sharma A, Zahoor A, Sharma S, Khuller GK, Prasad B.
Poly(DL-lactide-co-glycolide) nanoparticle-based inhalable sustained
drug delivery system for experimental tuberculosis. J Antimicrob
Chemother. 2003;52:981–986.
39. Zahoor A, Sharma S, Khuller GK. Inhalable alginate nanoparticles as
antitubercular drug carriers against experimental tuberculosis. Int J
Antimicrob Agents. 2005;26:298–303.
40. Esmaeili F, Hosseini-Nasr M, Rad-Malekshahi M, Samadi N,
Atyabi F, Dinarvand R. Preparation and antibacterial activity evalu-
ation of rifampicin-loaded poly lactide-co-glycolide nanoparticles.
Nanomedicine. 2007;3:161–167.
41. Ohashi K, Kabasawa T, Ozeki T, Okada H. One-step preparation
of rifampicin/poly(lactic-co-glycolic acid) nanoparticle-containing
mannitol microspheres using a four-fluid nozzle spray drier for
inhalation therapy of tuberculosis. J Control Release. 2009;135:
19–24.
42. Pandey R, Khuller GK. Solid lipid particle-based inhalable sustained
drug delivery system against experimental tuberculosis. Tuberculosis
(Edinb). 2005;85:227–234.
43. Wong JP, Yang H, Blasetti KL, Schnell G, Conley J, Schofield LN.
Liposome delivery of ciprofloxacin against intracellular Francisella
tularensis infection. J Control Release. 2003;92:265–273.
44. Sweeney LG, Wang Z, Loebenberg R, Wong JP, Lange CF, Finlay WH.
Spray-freeze-dried liposomal ciprofloxacin powder for inhaled aerosol
drug delivery. Int J Pharm. 2005;305:180–185.
45. Shah SP, Misra A. Development of liposomal amphotericin B dry
powder inhaler formulation. Drug Deliv. 2004;11:247–253.
46. Vyas SP, Quraishi S, Gupta S, Jaganathan KS. Aerosolized liposome-
based delivery of amphotericin B to alveolar macrophages. Int J Pharm.
2005; 296:12–25.
47. Khanna C, An de rs on PM, Hasz DE, Katsan is E, Nev il le M,
Klausner JS. Interleukin-2 liposome inhalation therapy is safe and
effective for dogs with spontaneous pulmonary metastases. Cancer.
1997;79:1409–1421.
48. Densmore CL, Kleinerman ES, Gautam A, et al. Growth suppres-
sion of established human osteosarcoma lung metastases in mice by
aerosol gene therapy with PEI-p53 complexes. Cancer Gene Ther.
2001;8:619–627.
49. Gautam A, Densmore CL, Waldrep JC. Inhibition of experimental
lung metastasis by aerosol delivery of PEI-p53 complexes. Mol Ther.
2000;2:318–323.
50. Koshkina NV, Agoulnik IY, Melton SL, Densmore CL, Knight V.
Biodistribution and pharmacokinetics of aerosol and intravenously
administered DNA-polyethyleneimine complexes: optimization of
pulmonary delivery and retention. Mol Ther. 2003;8:249–254.
51. Gautam A, Densmore CL, Melton S, Golunski E, Waldrep JC.
Aerosol delivery of PEI-p53 complexes inhibits B16-F10 lung
metastases through regulation of angiogenesis. Cancer Gene Ther.
2002;9:28–36.
52. Verschraegen CF, Gilbert BE, Loyer E, et al. Clinical evaluation of the
delivery and safety of aerosolized liposomal 9-nitro-20(s)-camptothecin
in patients with advanced pulmonary malignancies. Clin Cancer Res.
2004;10:2319–2326.
53. Shahiwala A, Misra A. A preliminary pharmacokinetic study of lipo-
somal leuprolide dry powder inhaler: a technical note. AAPS Pharm
Sci Tech. 2005;6:E482–E486.
54. Azarmi S, Tao X, Chen H, et al. Formulation and cytotoxicity of
doxorubicin nanoparticles carried by dry powder aerosol particles. Int
J Pharm. 2006;319:155–161.
55. Hwang SK, Jin H, Kwon JT, et al. Aerosol-delivered programmed
cell death 4 enhanced apoptosis, controlled cell cycle and suppressed
AP-1 activity in the lungs of AP-1 luciferase reporter mice. Gene Ther.
2007;14:1353–1361.
56. Jin H, Kim TH, Hwang SK, et al. Aerosol delivery of urocanic acid-
modified chitosan/programmed cell death 4 complex regulated apop-
tosis, cell cycle, and angiogenesis in lungs of K-ras null mice. Mol
Cancer Ther. 2006;5:1041–1049.
57. Taetz S, Nafee N, Beisner J, et al. The influence of chitosan content
in cationic chitosan/PLGA nanoparticles on the delivery efficiency of
antisense 2’-O-methyl-RNA directed against telomerase in lung cancer
cells. Eur J Pharm Biopharm. 2009;72:358–369.
58. Jere D, Xu CX, Arote R, Yun CH, Cho MH, Cho CS. Poly(beta-
amino ester) as a carrier for si/shRNA delivery in lung cancer cells.
Biomaterials. 2008;29:2535–2547.
59. Xu CX, Jere D, Jin H, et al. Poly(ester amine)-mediated, aerosol-
delivered Akt1 small interfering RNA suppresses lung tumorigenesis.
Am J Respir Crit Care Med. 2008;178:60–73.
60. Tomoda K, Ohkoshi T, Hirota K, et al. Preparation and properties of
inhalable nanocomposite particles for treatment of lung cancer. Colloids
Surf B Biointerfaces. 2009;71:177–182.
61. de Semir D, Petriz J, Avinyo A, et al. Non-viral vector-mediated uptake,
distribution, and stability of chimeraplasts in human airway epithelial
cells. J Gene Med. 2002;4:308–322.
62. Gilbert BE, Knight C, Alvarez FG, et al. Tolerance of volunteers to
cyclosporine A-dilauroylphosphatidylcholine liposome aerosol. Am J
Respir Crit Care Med. 1997;156:1789–1793.
63. Chougule M, Padhi B, Misra A. Nano-liposomal dry powder inhaler of
tacrolimus: preparation, characterization, and pulmonary pharmacoki-
netics. Int J Nanomedicine. 2007;2:675–688.
64. Bivas-Benita M, van Meijgaarden KE, Franken KL, et al. Pulmonary
delivery of chitosan-DNA nanoparticles enhances the immunogenicity
of a DNA vaccine encoding HLA-A*0201-restricted T-cell epitopes of
Mycobacterium tuberculosis. Vaccine. 2004;22:1609–1615.
65. Bivas-Benita M, Oudshoorn M, Romeijn S, et al. Cationic submicron
emulsions for pulmonary DNA immunization. J Control Release.
2004;100:145–155.
66. Kaipel M, Wagner A, Wassermann E, et al. Increased biological half-life
of aerosolized liposomal recombinant human Cu/Zn superoxide dis-
mutase in pigs. J Aerosol Med Pulm Drug Deliv. 2008;21:281–290.
67. Carpenter M, Epperly MW, Agarwal A, et al. Inhalation delivery
of manganese superoxide dismutase-plasmid/liposomes protects the
murine lung from irradiation damage. Gene Ther. 2005;12:685–693.
68. Epperly MW, Guo HL, Jefferson M, et al. Cell phenotype specific
kinetics of expression of intratracheally injected manganese superoxide
dismutase-plasmid/liposomes (MnSOD-PL) during lung radioprotective
gene therapy. Gene Ther. 2003;10:163–171.
69. Yamamoto H, Kuno Y, Sugimoto S, Takeuchi H, Kawashima Y. Surface-
modified PLGA nanosphere with chitosan improved pulmonary delivery
of calcitonin by mucoadhesion and opening of the intercellular tight
junctions. J Control Release. 2005;102:373–381.
70. Zhang Q, Shen Z, Nagai T. Prolonged hypoglycemic effect of insulin-
loaded polybutylcyanoacrylate nanoparticles after pulmonary admin-
istration to normal rats. Int J Pharm. 2001;218:75–80.
71. Huang YY, Wang CH. Pulmonary delivery of insulin by liposomal
carriers. J Control Release. 2006;113:9–14.
72. Bi R, Shao W, Wang Q, Zhang N. Spray-freeze-dried dry powder inha-
lation of insulin-loaded liposomes for enhanced pulmonary delivery.
J Drug Target. 2008;16:639–648.
73. Liu J, Gong T, Fu H, et al. Solid lipid nanoparticles for pulmonary
delivery of insulin. Int J Pharm. 2008;356:333–344.
74. Bai S, Thomas C, Ahsan F. Dendrimers as a carrier for pulmonary
delivery of enoxaparin, a low-molecular weight heparin. J Pharm Sci.
2007;96:2090–2106.
75. Bai S, Ahsan F. Synthesis and evaluation of pegylated dendrimeric
nanocarrier for pulmonary delivery of low molecular weight heparin.
Pharm Res. 2009;26:539–548.
76. Piras AM, Chiellini F, Fiumi C, et al. A new biocompatible nanopar-
ticle delivery system for the release of fibrinolytic drugs. Int J Pharm.
2008;357:260–271.
77. Plumley C, Gorman EM, El-Gendy N, Bybee CR, Munson EJ,
Berkland C. Nifedipine nanoparticle agglomeration as a dry powder
aerosol formulation strategy. Int J Pharm. 2009;369:136–143.
78. Almeida AJ, Souto E. Solid lipid nanoparticles as a drug delivery system
for peptides and proteins. Adv Drug Deliv Rev. 2007;59:478–490.

International Journal of Nanomedicine 2009:4
316
Mansour et al Dovepress
submit your manuscript | www.dovepress.com
Dovepress
79. Koping-Hoggard M, Varum KM, Issa M, et al. Improved chitosan-
mediated gene delivery based on easily dissociated chitosan
polyplexes of highly defined chitosan oligomers. Gene Ther. 2004;11:
1441–1452.
80. Howard KA, Rahbek UL, Liu X, et al. RNA interference in vitro and
in vivo using a novel chitosan/siRNA nanoparticle system. Mol Ther.
2006;14:476–484.
81. Grenha A, Seijo B, Remunan-Lopez C. Microencapsulated chitosan
nanoparticles for lung protein delivery. Eur J Pharm Sci. 2005;25:
427–437.
82. Issa MM, Koping-Hoggard M, Tommeraas K, et al. Targeted gene
delivery with trisaccharide-substituted chitosan oligomers in vitro
and after lung administration in vivo. J Control Release. 2006;115:
103–112.
83. Brzoska M, Langer K, Coester C, Loitsch S, Wagner TO,
Mallinckrodt C. Incorporation of biodegradable nanoparticles into
human airway epithelium cells-in vitro study of the suitability as a
vehicle for drug or gene delivery in pulmonary diseases. Biochem
Biophys Res Commun. 2004;318:562–570.
84. Sham JO, Zhang Y, Finlay WH, Roa WH, Lobenberg R. Formulation
and characterization of spray-dried powders containing nanoparticles
for aerosol delivery to the lung. Int J Pharm. 2004;269:457–467.
85. Kaul G, Amiji M. Tumor-targeted gene delivery using poly(ethylene
glycol)-modified gelatin nanoparticles: in vitro and in vivo studies.
Pharm Res. 2005;22:951–961.
86. Ely L, Roa W, Finlay WH, Lobenberg R. Effervescent dry powder for
respiratory drug delivery. Eur J Pharm Biopharm. 2007;65:346–353.
87. Beck-Broichsitter M, Gauss J, Packhaeuser CB, et al. Pulmonary drug
delivery with aerosolizable nanoparticles in an ex vivo lung model.
Int J Pharm. 2009;367:169–178.
88. Lynch J, Behan N, Birkinshaw C. Factors controlling particle size
during nebulization of DNA-polycation complexes. J Aerosol Med.
2007;20:257–268.
89. Chen J, Gao X, Hu K, et al. Galactose-poly(ethylene glycol)-poly-
ethylenimine for improved lung gene transfer. Biochem Biophys Res
Commun. 2008;375:378–383.
90. Nguyen J, Xie X, Neu M, et al. Effects of cell-penetrating peptides
and pegylation on transfection efficiency of polyethylenimine in
mouse lungs. J Gene Med. 2008;10:1236–1246.
91. Ziady AG, Gedeon CR, Muhammad O, et al. Minimal toxicity of
stabilized compacted DNA nanoparticles in the murine lung. Mol
Ther. 2003;8:948–956.
92. Ziady AG, Gedeon CR, Miller T, et al. Transfection of airway epithe-
lium by stable PEGylated poly-L-lysine DNA nanoparticles in vivo.
Mol Ther. 2003;8:936–947.
93. Kukowska-Latallo JF, Raczka E, Quintana A, Chen C, Rymaszewski M,
Baker JR Jr. Intravascular and endobronchial DNA delivery to murine
lung tissue using a novel, nonviral vector. Hum Gene Ther.
2000;11:1385–1395.
94. de Fougerolles AR. Delivery vehicles for small interfering RNA
in vivo. Hum Gene Ther. 2008;19:125–132.
95. Densmore CL. Advances in noninvasive pulmonary gene therapy.
Curr Drug Deliv. 2006;3:55–63.
96. De Smedt SC, Demeester J, Hennink WE. Cationic polymer based
gene delivery systems. Pharm Res. 2000;17:113–126.
97. Wightman L, Kircheis R, Rossler V, et al. Different behavior of
branched and linear polyethylenimine for gene delivery in vitro and
in vivo. J Gene Med. 2001;3:362–372.
98. Kichler A, Leborgne C, Coeytaux E, Danos O. Polyethylenimine-
mediated gene delivery: a mechanistic study. J Gene Med. 2001;3:
135–144.
99. Chollet P, Favrot MC, Hurbin A, Coll JL. Side-effects of a systemic
injection of linear polyethylenimine-DNA complexes. J Gene Med.
2002;4:84–91.
100. Tang MX, Szoka FC. The influence of polymer structure on the
interactions of cationic polymers with DNA and morphology of the
resulting complexes. Gene Ther. 1997;4:823–832.
101. Ogris M, Wagner E. Tumor-targeted gene transfer with DNA
polyplexes. Somat Cell Mol Genet. 2002;27:85–95.
102. Rudolph C, Schillinger U, Plank C, et al. Nonviral gene delivery
to the lung with copolymer-protected and transferrin-modified
polyethylenimine. Biochim Biophys Acta. 2002;1573:75–83.
103. Li SD, Huang L. Surface-modified LPD nanoparticles for tumor
targeting. Ann N Y Acad Sci. 2006;1082:1–8.
104. Eliyahu H, Joseph A, Schillemans JP, Azzam T, Domb AJ,
Barenholz Y. Characterization and in vivo performance of dextran-
spermine polyplexes and DOTAP/cholesterol lipoplexes administered
locally and systemically. Biomaterials. 2007;28:2339–2349.
105. Chono S, Li SD, Conwell CC, Huang L. An efficient and low immu-
nostimulatory nanoparticle formulation for systemic siRNA delivery
to the tumor. J Control Release. 2008;131:64–69.
106. Park MR, Kim HW, Hwang CS, et al. Highly efficient gene transfer
with degradable poly(ester amine) based on poly(ethylene glycol)
diacrylate and polyethylenimine in vitro and in vivo. J Gene Med.
2008;10:198–207.
107. Ko YT, Kale A, Hartner WC, Papahadjopoulos-Sternberg B,
Torchilin VP. Self-assembling micelle-like nanoparticles based
on phospholipid-polyethyleneimine conjugates for systemic gene
delivery. J Control Release. 2009;133:132–138.
108. Zeng XM, Martin GP, Marriott C. The controlled delivery of drugs
to the lung. Int J Pharm. 1995;124:149–164.
109. Muller RH, Mader K, Gohla S. Solid lipid nanoparticles (SLN) for
controlled drug delivery – a review of the state of the art. Eur J Pharm
Biopharm. 2000;50:161–177.
110. Schreier H, Gonzalez-Rothi RJ, Stecenko AA. Pulmonary delivery of
liposomes. J Control Release. 1993;24:209–223.
111. Taylor KMG, Taylor G, Kellaway IW, Stevens J. The stability of
liposomes to nebulisation. Int J Pharm. 1990;58:57–61.
112. Joshi M, Misra AN. Pulmonary disposition of budesonide from
liposomal dry powder inhaler. Methods Find Exp Clin Pharmacol.
2001;23:531–536.
113. Shah SP, Misra A. Liposomal amphotericin B dry powder inhaler:
effect of fines on in vitro performance. Pharmazie. 2004;59:
812–813.
114. White S, Bennett DB, Cheu S, et al. EXUBERA: pharmaceutical
development of a novel product for pulmonary delivery of insulin.
Diabetes Technol Ther. 2005;7:896–906.
115. Stribling R, Brunette E, Liggitt D, Gaensler K, Debs R. Aerosol
gene delivery in vivo. Proc Natl Acad Sci U S A. 1992;89:
11277–11281.
116. Alton EW, Middleton PG, Caplen NJ, et al. Non-invasive liposome-
mediated gene delivery can correct the ion transport defect in cystic
fibrosis mutant mice. Nat Genet. 1993;5:135–142.
117. Chadwick SL, Kingston HD, Stern M, et al. Safety of a single aerosol
administration of escalating doses of the cationic lipid GL-67/DOPE/
DMPE-PEG5000 formulation to the lungs of normal volunteers. Gene
Ther. 1997;4:937–942.
118. Oudrhiri N, Vigneron JP, Peuchmaur M, Leclerc T, Lehn JM,
Lehn P. Gene transfer by guanidinium-cholesterol cationic lipids
into airway epithelial cells in vitro and in vivo. Proc Natl Acad Sci
U S A. 1997;94:1651–1656.
119. Pillai R, Petrak K, Blezinger P, et al. Ultrasonic nebulization of cationic
lipid-based gene delivery systems for airway administration. Pharm
Res. 1998;15:1743–1747.
120. Densmore CL, Giddings TH, Waldrep JC, Kinsey BM, Knight V.
Gene transfer by guanidinium-cholesterol: dioleoylphosphatidyl-
ethanolamine liposome-DNA complexes in aerosol. J Gene Med.
1999;1:251–264.
121. Gautam A, Densmore CL, Waldrep JC. Pulmonary cytokine
responses associated with PEI-DNA aerosol gene therapy. Gene Ther.
2001;8:254–257.
122. Pitard B, Oudrhiri N, Lambert O, et al. Sterically stabilized BGTC-
based lipoplexes: structural features and gene transfection into the
mouse airways in vivo. J Gene Med. 2001;3:478–487.

International Journal of Nanomedicine 2009:4 317
Nanomedicine in pulmonary delivery
Dovepress
submit your manuscript | www.dovepress.com
Dovepress
123. Deshpande DS, Blanchard JD, Schuster J, et al. Gamma scintigraphic
evaluation of a miniaturized AERx pulmonary delivery system for
aerosol delivery to anesthetized animals using a positive pressure
ventilation system. J Aerosol Med. 2005;18:34–44.
124. Templeton NS. Nonviral delivery for genomic therapy of cancer. World
J Surg. 2009;33:685–697.
125. Morille M, Passirani C, Vonarbourg A, Clavreul A, Benoit JP. Progress
in developing cationic vectors for non-viral systemic gene therapy
against cancer. Biomaterials. 2008;29:3477–3496.
126. Cryan SA, Devocelle M, Moran PJ, Hickey AJ, Kelly JG. Increased
intracellular targeting to airway cells using octaarginine-coated
liposomes: In vitro assessment of their suitability for inhalation. Mol
Pharm. 2006;3:104–112.
127. Mehnert W, Mader K. Solid lipid nanoparticles: production,
characterization and applications. Adv Drug Deliv Rev. 2001;47:
165–196.
128. Schwarz C, Mehnert W, Lucks JS, M?ler RH. Solid lipid nanoparticles
(SLN) for controlled drug delivery. I. Production, characterization and
sterilization. J Control Release. 1994;30:83–96.
129. Westesen K. Novel lipid-based colloidal dispersions as potential drug
administration systems – expectations and reality. Colloid Polym Sci.
2000;278:608–618.
130. Muller RH, Ruhl D, Runge S, Schulze-Forster K, Mehnert W. Cyto-
toxicity of solid lipid nanoparticles as a function of the lipid matrix
and the surfactant. Pharm Res. 1997;14:458–462.
131. Heydenreich AV, Westmeier R, Pedersen N, Poulsen HS, Kristensen HG.
Preparation and purification of cationic solid lipid nanospheres–effects
on particle size, physical stability and cell toxicity. Int J Pharm.
2003;254:83–87.
132. Rudolph C, Schillinger U, Ortiz A, et al. Application of novel solid
lipid nanoparticle (SLN)-gene vector formulations based on a dimeric
HIV-1 TAT-peptide in vitro and in vivo. Pharm Res. 2004;21:
1662–1669.
133. Videira MA, Gano L, Santos C, Neves M, Almeida AJ. Lymphatic
uptake of lipid nanoparticles following endotracheal administration.
J Microencapsul. 2006;23:855–862.
134. Videira MA, Botelho MF, Santos AC, Gouveia LF, de Lima JJ,
Almeida AJ. Lymphatic uptake of pulmonary delivered radiolabelled
solid lipid nanoparticles. J Drug Target. 2002;10:607–613.
135. Liu F, Yang J, Huang L, Liu D. Effect of non-ionic surfactants on the
formation of DNA/emulsion complexes and emulsion-mediated gene
transfer. Pharm Res. 1996;13:1642–1646.
136. Yi SW, Yune TY, Kim TW, et al. A cationic lipid emulsion/DNA
complex as a physically stable and serum-resistant gene delivery
system. Pharm Res. 2000;17:314–320.
137. Kim TW, Chung H, Kwon IC, Sung HC, Jeong SY. In vivo gene
transfer to the mouse nasal cavity mucosa using a stable cationic lipid
emulsion. Mol Cells. 2000;10:142–147.
138. Boas U, Heegaard PM. Dendrimers in drug research. Chem Soc Rev.
2004;33:43–63.
139. Rudolph C, Lausier J, Naundorf S, Muller RH, Rosenecker J.
In vivo gene delivery to the lung using polyethylenimine and fractured
polyamidoamine dendrimers. J Gene Med. 2000;2:269–278.
140. Hickey AJ. Lung deposition and clearance of pharmaceutical aerosols:
what can be learned from inhalation toxicology and industrial hygiene?
Aerosol Sci Technol. 1993;18:290–304.
141. Hickey AJ, Mansour HM. Delivery of drugs by the pulmonary
route. In: Florence AT, Siepmann J, editors. Modern Pharmaceutics.
New York, NY: Taylor and Francis, Inc.; 2008. p. 191–219.
142. Merisko-Liversidge E, McGurk SL, Liversidge GG. Insulin nanopar-
ticles: a novel formulation approach for poorly water soluble Zn-
insulin. Pharm Res. 2004;21:1545–1553.
143. Rabinow BE. Nanosuspensions in drug delivery. Nat Rev Drug Discov.
2004;3:785–796.
144. Mosén K, Báckstrom K, Thalberg K. Particle formation and capture
during spray drying of inhalable particles. Pharm Dev Technol.
2004;9:409–418.
145. Duddu SP, Sisk SA, Walter YH, et al. Improved lung delivery from a
passive dry powder inhaler using an Engineered PulmoSphere powder.
Pharm Res. 2002;19:689–695.
146. Maa YF, Nguyen PA, Sit K, Hsu CC. Spray-drying performance
of a bench-top spray dryer for protein aerosol powder preparation.
Biotechnol Bioeng. 1998;60:301–309.
147. Freitas S, Merkle HP, Gander B. Ultrasonic atomisation into
reduced pressure atmosphere – envisaging aseptic spray-drying for
microencapsulation. J Control Release. 2004;95:185–195.
148. Stahl K, Claesson M, Lilliehorn P, Linden H, Backstrom K. The
effect of process variables on the degradation and physical prop-
erties of spray dried insulin intended for inhalation. Int J Pharm.
2002;233:227–237.
149. Gilani K, Najafabadi AR, Barghi M, Rafiee-Tehrani M. The effect of
water to ethanol feed ratio on physical properties and aerosolization
behavior of spray dried cromolyn sodium particles. J Pharm Sci.
2005;94:1048–1059.
150. Vidgren MT, Vidgren PA, Paronen TP. Comparison of physical and
inhalation properties of spray-dried and mechanically micronized
disodium cromoglycate. Int J Pharm. 1987;35:139–144.
151. US Food and Drug Administration. Guidance for industry: metered
dose inhaler (MDI) and dry powder inhaler (DPI) drug products –
chemistry, manufacturing, and controls documentation. Rockville,
IN: US Department of Health and Human Services; 1998.
152. Kawashima Y, Serigano T, Hino T, Yamamoto H, Takeuchi H. Effect
of surface mor phology of carrier lactose on dry powder inhalation
property of pranlukast hydrate. Int J Pharm. 1998;172:179–188.
153. Vanderbist F, Wery B, Pavon IM, Moes AJ. Optimization of a dry
powder inhaler formulation of nacystelyn, a new mucoactive agent.
J Pharm Pharmacol. 1999;51:1229–1234.
154. Steckel H, Bolzen N. Alternative sugars as potential carriers for dry
powder inhalations. Int J Pharm. 2004;270:297–306.
155. Harjunen P, Lankinen T, Salonen H, Lehto VP, Jarvinen K. Effects
of carriers and storage of formulation on the lung deposition of
a hydrophobic and hydrophilic drug from a DPI. Int J Pharm.
2003;263:151–163.
156. Rogers T, Johnston K, Williams R. Solution-based particle formation
of pharmaceutical powders by supercritical or compressed Fluid CO2
and cryogenic spray-freezing technologies. Drug Dev Ind Pharm.
2001;27:1003–1016.
157. Maa YF, Prestrelski SJ. Biopharmaceutical powders: particle for-
mation and formulation considerations. Curr Pharm Biotechnol.
2000;1:283–302.
158. Maa YF, Nguyen PA, Sweeney T, Shire SJ, Hsu CC. Protein inha-
lation powders: spray drying vs spray freeze drying. Pharm Res.
1999;16:249–254.
159. Yu Z, Garcia AS, Johnston KP, Williams RO, 3rd. Spray freezing into
liquid nitrogen for highly stable protein nanostructured microparticles.
Eur J Pharm Biopharm. 2004;58:529–537.
160. Kuo JH, Hwang R. Preparation of DNA dry powder for non-viral gene
delivery by spray-freeze drying: effect of protective agents (polyeth-
yleneimine and sugars) on the stability of DNA. J Pharm Pharmacol.
2004;56:27–33.
161. Tom JW, Debenedetti PG. Particle formation with supercritical fluids-a
review. J Aerosol Sci. 1991;22:555–584.
162. Rehman M, Shekunov BY, York P, et al. Optimisation of powders for
pulmonary delivery using supercritical fluid technology. Eur J Pharm
Sci. 2004;22:1–17.
163. Steckel H, Thies J, Muller BW. Micronizing of steroids for pul-
monary delivery by supercritical carbon dioxide. Int J Pharm.
1997;152:99–110.
164. Steckel H, Muller BW. Metered-dose inhaler formulation of flutica-
sone-17-propionate micronized with supercritical carbon dioxide using
the alternative propellant HFA-227. Int J Pharm. 1998;173:25–33.
165. Shekunov BY, Chattopadhyay P, Seitzinger J, Huff R. Nanoparticles
of poorly water-soluble drugs prepared by supercritical fluid extraction
of emulsions. Pharm Res. 2006;23:196–204.

International Journal of Nanomedicine 2009:4
318
Mansour et al Dovepress
submit your manuscript | www.dovepress.com
Dovepress
166. Chattopadhyay P, Huff R, Shekunov BY. Drug encapsulation
using supercritical fluid extraction of emulsions. J Pharm Sci.
2006;95:667–679.
167. El-Baseir MM, Phipps MA, Kellaway IW. Preparation and
subsequent degradation of poly(l-lactic acid) microspheres suitable
for aerosolisation: a physico-chemical study. Int J Pharm. 1997;151:
145–153.
168. Rasenack N, Steckel H, Muller BW. Micronization of anti-
inflammatory drugs for pulmonary delivery by a controlled crystal-
lization process. J Pharm Sci. 2003;92:35–44.
169. Chow AHL, Tong HHY, Chattopadhyay P, Shekunov BY.
Particle engineering for pulmonary drug delivery. Pharm Res.
2007;24:411–437.
170. Gratton SEA, Pohlhaus PD, Lee J, Guo J, Cho MJ, DeSimone JM.
Nanofabricated particles for engineered drug therapies: A preliminary
biodistribution study of PRINT™ nanoparticles. J Control Release.
2007;121:10–18.
171. Gratton SE, Ropp PA, Pohlhaus PD, et al. The effect of particle
design on cellular internalization pathways. Proc Natl Acad Sci U S A.
2008;105:11613–11618.
172. Gratton SE, Napier ME, Ropp PA, Tian S, DeSimone JM. Microfab-
ricated particles for engineered drug therapies: elucidation into the
mechanisms of cellular internalization of PRINT particles. Pharm
Res. 2008;25:2845–2852.
173. Li X, Blondino FE, Hindle M, Soine WH, Byron PR. Stability and
characterization of perphenazine aerosols generated using the capillary
aerosol generator. Int J Pharm. 2005;303:113–124.
174. Avram MJ, Henthorn TK, Spyker DA, et al. Recirculatory pharma-
cokinetic model of the uptake, distribution, and bioavailability of
prochlorperazine administered as a thermally generated aerosol in a
single breath to dogs. Drug Metab Dispos. 2007;35:262–267.
175. Rabinowitz JD, Wensley M, Lloyd P, et al. Fast onset medications
through thermally generated aerosols. J Pharmacol Exp Ther.
2004;309:769–775.
176. Hong JN, Hindle M, Byron PR. Control of particle size by coagulation
of novel condensation aerosols in reservoir chambers. J Aerosol Med.
2002;15:359–368.
177. Gupta R, Hindle M, Byron PR, Cox KA, McRae DD. Investigation
of a novel condensation aerosol generator: solute and solvent effects.
Aerosol Sci Technol. 2003;37:672–681.
178. Rabinowitz JD, Lloyd PM, Munzar P, et al. Ultra-fast absorption of
amorphous pure drug aerosols via deep lung inhalation. J Pharm Sci.
2006;95:2438–2451.
179. Myers DJ, Timmons RD, Lu AT, et al. The effect of film thickness
on thermal aerosol generation. Pharm Res. 2007;24:336–342.
180. Hickey AJ, Mansour HM, Telko MJ, et al. Physical characterization
of component particles included in dry powder inhalers. I. Strategy
review and static characteristics. J Pharm Sci. 2007;96:1282–1301.
181. Williams RO, 3rd, Brown J, Liu J. Influence of micronization
method on the performance of a suspension triamcinolone acetonide
pressurized metered-dose inhaler formulation. Pharm Dev Technol.
1999;4:167–179.
182. Barry PW, O’Callaghan C. An in vitro analysis of the output of
budesonide from different nebulizers. J Allergy Clin Immunol.
1999;104:1168–1173.
183. Schauer JJ, Christensen CG, Kittelson DB, Johnson JP, Watts WF.
Impact of ambient temperatures and driving conditions on the
chemical composition of particulate matter emissions from non-
smoking gasoline-powered motor vehicles. Aerosol Sci Technol.
2008;42:210–223.
184. Miguel A, Eiguren-Fernandez A, Sioutas C, Fine P, Geller M,
Mayo P. Observations of twelve USEPA priority polycyclic aromatic
hydrocarbons in the aitken size range (10–32 nm Dp). Aerosol Sci
Technol. 2005;39:415–418.
185. Park K, Cao F, Kittelson DB, McMurry PH. Relationship between
particle mass and mobility for diesel exhaust particles. Environ Sci
Technol. 2003;37:577–583.
186. Sardar SB, Fine PM, Mayo PR, Sioutas C. Size-fractionated
measurements of ambient ultrafine particle chemical composition
in Los Angeles using the NanoMOUDI. Environ Sci Technol.
2005;39:932–944
187. Lin CC, Chen SJ, Huang KL. Characteristics of metals in nano/ultra-
fine/fine/coarse particles collected beside a heavily trafficked road.
Environ Sci Technol. 2005;39:8113–8122.
188. Geller MD, Kim S, Misra C, Sioutas C, Olson BA, Marple VA.
A methodology for measuring size-dependent chemical composition
of ultrafine particles. Aerosol Sci Technol. 2002;36:748–762.
189. Venkatachari P, Hopke PK, Brune WH, et al. Characterization of
wintertime reactive oxygen species concentrations in Flushing,
New York. Aerosol Sci Technol. 2007;41:97–111.
190. Fujitani Y, Hasegawa S, Fushimi A, et al. Collection characteristics
of low-pressure impactors with various impaction substrate materials.
Atmos Environ. 2006;40:3221–3229.
191. Bates S, Zografi G, Engers D, Mor ris K, Crowley K, Newman A.
Analysis of amorphous and nanocrystalline solids from their X-ray
diffraction patterns. Pharm Res. 2006;23:2333–2349.
192. Larhrib H, Zeng XM, Martin GP, Marriott C, Pritchard J. The use
of different grades of lactose as a carrier for aerosolised salbutamol
sulphate. Int J Pharm. 1999;191:1–14.
193. Traini D, Young PM, Thielmann F, Acharya M. The influence of lactose
pseudopolymorphic form on salbutamol sulfate-lactose interactions
in DPI formulations. Drug Dev Ind Pharm. 2008;34:992–1001.
194. Newman AW, Byrn SR. Solid-state analysis of the active
pharmaceutical ingredient in drug products. Drug Discov Today.
2003;8:898–905.
195. Saleki-Gerhardt A, Ahlneck C, Zografi G. Assessment of disorder in
crystalline solids. Int J Pharm. 1994;101:237–247.
196. Bunker M, Davies M, Roberts C. Towards screening of inhalation
formulations: measuring interactions with atomic force microscopy.
Expert Opin Drug Deliv. 2005;2:613–624.
197. Sethuraman VV, Hickey AJ. Powder properties and their influence on
dry powder inhaler delivery of an antitubercular drug. AAPS Pharm
Sci Tech. 2002;3:E28.
198. Mansour HM, Zografi G. The relationship between water vapor absorp-
tion and desorption by phospholipids and bilayer phase transitions.
J Pharm Sci. 2007;96:377–396.
199. Agu RU, Ugwoke MI, Armand M, Kinget R, Verbeke N. The lung
as a route for systemic delivery of therapeutic proteins and peptides.
Respir Res. 2001;2:198–209.
200. Groneberg DA, Witt C, Wagner U, Chung KF, Fischer A. Fundamen-
tals of pulmonary drug delivery. Respir Med. 2003;97:382–387.
201. Mathias NR, Yamashita F, Lee VHL. Respiratory epithelial cell culture
models for evaluation of ion and drug transport. Adv Drug Deliv Rev.
1996;22:215–249.
202. Forbes B, Ehrhardt C. Human respiratory epithelial cell culture for drug
delivery applications. Eur J Pharm Biopharm. 2005;60:193–205.
203. Sakagami M. In vivo, in vitro and ex vivo models to assess pulmo-
nary absorption and disposition of inhaled therapeutics for systemic
delivery. Adv Drug Deliv Rev. 2006;58:1030–1060.
204. Mobley C, Hochhaus G. Methods used to assess pulmonary deposition
and absorption of drugs. Drug Discov Today. 2001;6:367–375.
205. Steimer A, Haltner E, Lehr CM. Cell culture models of the respi-
ratory tract relevant to pulmonary drug delivery. J Aerosol Med.
2005;18:137–182.
206. Borchard G, Cassará ML, Roemelé PEH, Florea BI, Junginger HE.
Transport and local metabolism of budesonide and fluticasone pro-
pionate in a human bronchial epithelial cell line (Calu-3). J Pharm
Sci. 2002;91:1561–1567.
207. Ehrhardt C, Fiegel J, Fuchs S, et al. Drug absorption by the respiratory
mucosa: cell culture models and particulate drug carriers. J Aerosol
Med. 2002;15:131–139.
208. Foster KA, Avery ML, Yazdanian M, Audus KL. Characterization of
the Calu-3 cell line as a tool to screen pulmonary drug delivery. Int J
Pharm. 2000;208:1–11.

International Journal of Nanomedicine 2009:4
International Journal of Nanomedicine
Publish your work in this journal
Submit your manuscript here: http://www.dovepress.com/international-journal-of-nanomedicine-journal
The International Journal of Nanomedicine is an international, peer-
reviewed journal focusing on the application of nanotechnology
in diagnostics, therapeutics, and drug delivery systems throughout
the biomedical field. This journal is indexed on PubMed Central,
MedLine, CAS, SciSearch®, Current Contents®/Clinical Medicine,
Journal Citation Reports/Science Edition, EMBase, Scopus and the
Elsevier Bibliographic databases. The manuscript management system
is completely online and includes a very quick and fair peer-review
system, which is all easy to use. Visit http://www.dovepress.com/
testimonials.php to read real quotes from published authors.
319
Nanomedicine in pulmonary delivery
Dovepress
submit your manuscript | www.dovepress.com
Dovepress
Dovepress
209. Foster KA, Oster CG, Mayer MM, Avery ML, Audus KL.
Characterization of the A549 cell line as a type ii pulmonary epithelial
cell model for drug metabolism. Exp Cell Res. 1998;243:359–366.
210. Manford F, Tronde A, Jeppsson AB, Patel N, Johansson F, Forbes B.
Drug permeability in 16HBE14o-airway cell layers correlates with
absorption from the isolated perfused rat lung. Eur J Pharm Sci.
2005;26:414–420.
211. Lin H, Li H, Cho HJ, et al. Air-liquid interface (ALI) culture of human
bronchial epithelial cell monolayers as an in vitro model for airway
drug transport studies. J Pharm Sci. 2007;96:341–350.
212. Vaughn JM, McConville JT, Burgess D, et al. Single dose and multiple
dose studies of itraconazole nanoparticles. Eur J Pharm Biopharm.
2006;63:95–102.
213. Yang W, Tam J, Miller DA, et al. High bioavailability from nebulized
itraconazole nanoparticle dispersions with biocompatible stabilizers.
Int J Pharm. 2008;361:177–188.
214. McConville JT, Overhoff KA, Sinswat P, et al. Targeted high lung
concentrations of itraconazole using nebulized dispersions in a murine
model. Pharm Res. 2006;23:901–911.
215. Mizuno T, Mohri K, Nasu S, Danjo K, Okamoto H. Dual imag-
ing of pulmonary delivery and gene expression of dry powder
inhalant by fluorescence and bioluminescence. J Control Release.
2009;134:149–154.
216. Oberdorster G, Sharp Z, Atudorei V, et al. Extrapulmonary translo-
cation of ultrafine carbon particles following whole-body inhalation
exposure of rats. J Toxicol Environ Health A. 2002;65:1531–1543.
217. Heckel K, Kiefmann R, Dorger M, Stoeckelhuber M, Goetz AE.
Colloidal gold particles as a new in vivo marker of early acute lung
injury. Am J Physiol Lung Cell Mol Physiol. 2004;287:L867–L878.
218. Kato T, Yashiro T, Murata Y, et al. Evidence that exogenous substances
can be phagocytized by alveolar epithelial cells and transported into
blood capillaries. Cell Tissue Res. 2003;311:47–51.
219. Oberdorster G, Sharp Z, Atudorei V, et al. Translocation of inhaled
ultrafine particles to the brain. Inhal Toxicol. 2004;16:437–445.
220. Oberdorster G. Toxicology of ultrafine particles: in vivo studies. Philos
Trans R Soc Lond A. 2000;358:2719–2740.
221. Ballou B, Lagerholm BC, Ernst LA, Bruchez MP, Waggoner AS.
Noninvasive imaging of quantum dots in mice. Bioconjug Chem.
2004;15:79–86.
222. Oberdorster G, Oberdorster E, Oberdorster J. Nanotoxicology: an
emerging discipline evolving from studies of ultrafine particles.
Environ Health Perspect. 2005;113:823–839.
223. Kreyling WG, Semmler M, Erbe F, et al. Translocation of ultrafine
insoluble iridium particles from lung epithelium to extrapulmonary
organs is size dependent but very low. J Toxicol Environ Health A.
2002;65:1513–1530.
224. Oberdorster G, Ferin J, Morrow PE. Volumetric loading of alveolar
macrophages (AM): a possible basis for diminished AM-mediated
particle clearance. Exp Lung Res. 1992;18:87–104.
225. Oberdorster G, Finkelstein JN, Johnston C, et al. Acute pulmonary
effects of ultrafine particles in rats and mice. Res Rep Health Eff Inst.
2000;5–74; disc 75–86.
226. Ferin J, Oberdorster G, Soderholm SC, Gelein R. Pulmonary tissue
access of ultrafine particles. J Aerosol Med. 1991;4:57–68.
227. Hickey AJ, Mansour HM. Formulation challenges of powders for
the delivery of small molecular weight molecules as aerosols. In:
Rathbone MJ, Hadgraft J, Roberts MS, Lane ME, editors. Modified-
release Drug Delivery Technology. New York, NY: Informa Health-
care; 2008. p. 573–601.