Nanomaterials for Wound Healing: Scope and Advancement

Abstract

Innovative methods for treating impaired and hard-to-heal wounds are needed. Novel strategies are needed for faster healing by reducing infection, moisturizing the wound, stimulating the healing mechanisms, speeding up the wound closure and reducing scar formation. In the past few years, nanotechnology has been constantly revolutionizing the treatment and management of wound care, by offering novel solutions which include but are not limited to: state-of-the-art materials, so called 'smart' biomaterials and theranostic nanoparticles. Nanotechnology-based therapy has recently announced itself as a possible next-generation therapy that is able to advance wound healing to cure chronic wounds. In this communication, the recent progress in advanced therapy for cutaneous wound healing during last 5 years using a nanotechnology-based approach is summarized.

Full text

2593Nanomedicine (Lond.) (2015) 10(16), 2593–2612 ISSN 1743-5889
part of
Review
10.2217/NNM.15.82 © 2015 Future Medicine Ltd
Nanomedicine (Lond.)
Review 2015/07/30
10
16
2015
Innovative methods for treating impaired and hard-to-heal wounds are needed.
Novel strategies are needed for faster healing by reducing infection, moisturizing
the wound, stimulating the healing mechanisms, speeding up the wound closure and
reducing scar formation. In the past few years, nanotechnology has been constantly
revolutionizing the treatment and management of wound care, by offering novel
solutions which include but are not limited to: state-of-the-art materials, so called
‘smart’ biomaterials and theranostic nanoparticles. Nanotechnology-based therapy
has recently announced itself as a possible next-generation therapy that is able to
advance wound healing to cure chronic wounds. In this communication, the recent
progress in advanced therapy for cutaneous wound healing during last 5 years using
a nanotechnology-based approach is summarized.
Keywords: nanomaterials (polymer, carbon-based, lipid-contained, ceramic, metallic, metal
oxides) • scaffolds with embedded nanomaterials • wound-healing therapy
Wound healing is a process of repairing dam-
aged tissue, and restoring its integrity. This
process involves a series of biochemical and
physiological events which distinguishes
four distinct, sometimes overlapping phases.
The phases are driven by a list of bioactive
molecules and mediators (specific for every
phase) [1,2] : hemostasis, inflammation, pro-
liferation (proliferation, granulation and
contraction) and remodeling. Hemostasis
includes vasoconstriction (to limit bleeding,
activation of coagulation), and complement
cascades (platelet activation, adhesion and
aggregation, and clot formation). Inflam-
mation is a defense mechanism in which
the wound is cleaned and rebuilding begins
through vasodilation and macrophage activa-
tion. Slowing in this stage makes inflamma-
tion persistent and results in impaired wound
healing. Epithelialization, angiogenesis,
granulation tissue formation and provisional
matrix deposition are the principal steps in
the proliferative phase of wound healing.
Neovascularization of the wound is a cru-
cial part of the normal healing process so
new blood vessels can supply injured tissues
with oxygen, nutrients and essential growth
factors. Angiogenesis and vasculogenesis
are processes of new blood vessel formation
either from pre-existing vessesls or by de novo
generation of endothelial cells. The main
feature of remodeling is the deposition of
extracellular matrix (ECM) in an organized
and well-mannered network, myofibrolasts
formation and then contraction of wound [3] .
Any alteration and complications during the
wound-healing process may lead to a chronic
ulcer that fails to heal. In recent years,
approximately 84% (number one cause) of
diabetic patients were hospitalized due to
lower extremity foot ulcers [4] . Many factors
can impair wound healing. First, lifestyle
(alcoholism and smoking, among others) and
age of the subjects have a huge influence on
the rate of wound closing (10–14 days). Fur-
thermore, health conditions of patient, such
as high cholesterol level, diabetes, peripheral
arterial disease, Ehlers–Danlos syndrome,
Cutis Laxa, hypothyroidism, homocystin-
uria and advanced stage of the diseases are
Nanomaterials for wound healing: scope
and advancement
Irina Kalashnikova1, Soumen
Das*,1 & Sudipta Seal**,1,2
1Nanoscience Technology Center,
Advanced Materials Processing
& Analysis Center, University of Central
Florida, 12424 Research Parkway, Suite
400, Orlando, FL 32826, USA
2Materials Science & Engineering, College
of Medicine, Universit y of Central Florida,
Orlando, FL 32816, USA
*Author for correspondence:
Tel.: +1 407 882 1174
Fax: +1 407 882 1175
Soumen.Das@ucf.edu
**Author for correspondence:
Tel.: +1 407 823 5277
Fax: +1 407 882 1156
Sudipta.Seal@ucf.edu
For reprint orders, please contact: reprints@futuremedicine.com

2594 Nanomedicine (Lond.) (2015) 10(16 ) future science group
Review Kalashnikova, Das & Seal
other group of factors that can delay wound healing [5 ] .
Recent advancement in medicine, pharmaceutical sci-
ences, bioengineering chemistry, nanotechnology sci-
ences has brought several new strategies that minimize
any complications associated with wound healing and
improve the wound management.
Nowadays, a wide choice of therapy is provided by
conventional and modern approaches to wound treat-
ments. Conventional therapy implies debridement and
dressing change. Various types of dressing are used for
wound healing. The types of dressings can be catego-
rized in three types: traditional dressings, biomaterial-
based dressings and artificial dressings [6 ]. A gauze and
gauze/cotton composites with a nonadhesive or an
adhesive inner surface, can be considered an example
of traditional dressing. Biomaterial-based dressing can
mainly be classified as allografts, tissue derivatives
and xenografts. Fresh or freeze-dried skin fragments,
like scalp tissues or amniotic membrane taken from
the patient’s relatives or cadavers, represents the most
common allograft dressing. These simple examples of
tissue derivates and xenografts are dressings derived
from different forms of collagen and from pig skin,
respectively. Artificial dressings can be in the form of
film, membrane, foam, gel, composite and spray. Many
are from natural sources but are used in the prepara-
tion of artificial dressing (collagen, cellulose, alginate
substitutes, fibrin, chitosan, hyaluronic acid, carboxy-
methylcellulose, collagen, gelatin, polyurethanes and
new-age biopolymers) [6 –10] . Some biocompatible and
biodegradable synthetic polymers (polyglycolic acid,
polylactic acid, polyacrylic acid, polycaprolactone,
polyvinylpyrrolidone, polyvinyl alcohol, polyethylene
glycol) with excellent mechanical properties are also
reported to enhance the wound closure, by enhanc-
ing re-epithelialization, inducing cell proliferation,
migration and differentiation using in vitro and in vivo
wound-healing model [8] .
There are commercially created skin substitutes
reported for the treatment of skin wounds and inju-
ries [10] . Some of the commercially available wound-
healing dressings have been mentioned in a review
written by Boateng et al. [11] . Wound dressings with
capabilities to manage bacterial infection with sys-
temic antibiotic loads are commercially available [8,12] .
Advanced therapy includes: tissue-engineered wound
beds (decellularized tissue scaffolds, hydrogels, bi-
layered skin substitutes and fibroblast-seeded or fibro-
blasts/keratinocyte-seeded scaffold) [10, 13, 14] , proteases,
drugs, stem cells (endothelial progenitor and mesen-
chymal stem cells) [1 2 ,14 –17] , genes [15 ,18,19] and growth
factors therapy (EGF, KGF, TGF1α/β transform-
ing growth factors [TGFs], VEGF, PDGF) [10 ,13,18]
or combination of stem cells/growth factor or gene
therapy [15, 16] . Other type of advanced wound care
strategies are [1, 13] : hyperbaric oxygen therapy, vac-
uum-compression therapy, negative pressure wound
therapy, ultrasound noncontact wound-healing device
(MIST), electrostimulation, electromagnetic therapy,
hydrotherapy, lasers and light-emitting diodes [1, 20] .
Wound-healing therapy based on utilization of
nanomaterials (NMs) has demonstrated new promises
and benefits in this field. A variety of nanotechnol-
ogy platforms have been developed such as fullerenes,
nanotubes, quantum dots, nanopores, dendrimers,
liposomes, metallic, ceramic and magnetic, nanoemul-
sions and polymer nanoparticles [ 21] . Nanomedicine
has extensively proven to have excellent potential by
utilizing nanoscale objects for drug and gene delivery,
biosensors, advanced imaging, tissue regeneration,
diagnostics, cancer and other disease treatments [2 ,22–
23] . Unique properties of NMs and their biomimetic
advantages and engineering applications for bone,
cartilage, vascular, neural and bladder tissue are
overviewed in this literature [2 ,24 –26] .
NM-based wound-healing therapy
Currently, it is possible to distinguish two types of
NMs for wound-healing therapy. NMs which are able
to heal due to the features of nano-scaled material or
NMs as a cargo for delivering therapeutic agents [2] .
Figure 1 represents an analysis of different NM-based
treatments in literature for cutaneous wound healing
during the last 5 years. In this review, nanotechnology-
based products used in wound healing were divided
into five groups according to NM composition: poly-
mer, carbon-based, lipids-contained, ceramic, metal
and metal oxide nanoparticles and different types
of scaffolds with embedded NMs. All types of NMs
used for wound care are shown in Figure 2. This fig-
ure also outlines the beneficial effects of different NMs
on the phase/s of wound healing. Tab l e 1 summarizes
the different NMs which have been investigated for
management of wound care. It is interesting to men-
tion that there are differently established in vitro and
in vivo would healing models which have been prac-
ticed in various studies. These model systems are vital
when comparing the healing efficacy of the NM as the
size and number of wounds in an animal can influ-
ence the outcome. Figure 3 presents whole spectra of
in vitro and in vivo wound model systems exposed to
NM treatments, incision types and methods of NM
administration.
The effects of different NMs and potency to wound
healing are dissimilar, and largely depend on NM
physicochemical properties. Some key properties of
NMs which can influence the outcome for wound
healing are: biomaterial property, size, colloidal sta-

www.futuremedicine.com 2595
Figure 1. Number of publications regarding wound-
healing therapy using different nanomaterials. This
figure reveals that highest number of publications
explored with metal/metal oxide NMs and the least
number of publications tested carbon NMs for their
efficacy in wound care. Lipid vehicles and polymer NPs
have also been studied for different applications in
wound repair.
NM: Nanomaterial; NP: Nanoparticle.
Me/Me oxide NPs
Lipid vehicles
Carbon NMs
Ceramic NPs
Polymer NPs
39%
7%
14%
19%
21%
future science group
Nanomaterials for wound healing: scope & advancement Review
bility, surface functionalization and surface charge.
Ability to biodegrade and biocompatibility of NMs
has additional advantages over particles which can-
not be digested and deposited in body. Other than the
physiochemical property, presence of a payload (active
ingredient) with NMs having wound-healing activity
is definitely beneficial.
Commonly, size of NM defines a mechanism of
internalization of NM in the cell. Small size (3–15 nm)
provides a passive diffusion pathway for NMs uptake
by cells. Transferring cargo directly to the cytoplasm
can guarantee safe delivery of its payload to cell. Stabil-
ity of NMs in the vehicle (pure water, PBs or others)
plays an important role for administration of the NMs
(injection, IV and topical, among others). Although,
NMs with size range 100–200 nm have been used
more often than NMs with other dimensions for
wound care applications (Tab l e 1 ) . The stability of
NMs in the extracellular fluid will prevent aggrega-
tion that may help avoid NM cytotoxicity. Impurities
(solvent used during the synthesis, stabilizer and/or
impurities in the precursor) in NMs also can affect the
cell–NMs interaction and affect the outcome. Next,
the amount and type of functional group/s on the NM
surface can provide bonuses for loading active ingre-
dients and also contribute/s to the surface charge of
the material. Last, morphology and shape of the NMs
are known to impact the cell nanoparticles interaction
and internalization as well. Other than the key features
discussed above, crystallinity and shape of the NMs
can also play a crucial role in acceleration of wound
closure. NM with optimized parameters in a combina-
tion with medications or other payload can bring desir-
able outcome for treatment of complicated wounds
(hard-to-heal and ischemic wounds).
The cellular and molecular mechanisms of wound
healing are well described in the literature [63,6 4]. How-
ever, to the best of our knowledge only one manu-
script identified the mechanism of NMs action or
pathway studied the application of NMs in the area
of wound healing [65] . Several signaling pathways that
can be related to wound-healing process are discussed
in [27–3 0, 66,67]: JNK, EMR, WnT, PI3k/AkT/mTOR,
TGF-β. The short list of the most common protein/
gene regulation below can be suggested for an evalua-
tion during wound healing to outline the mechanism
of action: reactive oxygen species (ROS), growth fac-
tors (FGF, EGF, SDF-1α, KGF, VEGF, PDGF), NFκB
(nuclear factor kappa-light-chain-enhancer of activated
B cells), TGF-β/α, TNF, IL (-1, -6, -8 and -10), PGE2,
enzymes (matrix metalloproteinases, myeloperoxidase
(MPO), glutathione peroxidase (GPO), protein mole-
cules related to attachment or remodeling of the matrix
(angiopoietin-1, L-selectin and intercellular adhesion
molecule-1, tissue inhibitors of metalloproteinase,
angiogenin, collagen type I and III, fibrinogen) [3] .
Polymer NM therapy
Nanoparticles used for wound-healing applications
are often based on polymer materials that have been
used as dressings [8,10] or have successfully proven
themselves for drug delivery, bioimaging and biosens-
ing assays applications [3 1] . For example, poly (lac-
tide-co-glycolide) (PLGA), polycaprolactone (PCL)
and PEG are three synthetic polymers that have been
used to engineer biomaterials for wound care applica-
tions. PLGA-curcumin nanoparticles showed twofold
increase in wound-healing capability compared with
that of PLGA or curcumin. Curcumin has shown its
abilities for anti-inflammatory, antioxidant and anti-
infective properties [68, 69] . PLGA nanoparticles loaded
with curcumin quenched ROS, inhibited MPO, down-
regulated the expression of anti-oxidative enzymes like
glutathione peroxidase and NF-κβ that minimized
the inflammatory responses, expedited re-epitheliali-
zation and improved granulation tissue formation [70] .
It is important to note that the illustration provided
in this study [70] explains the phases of wound heal-
ing regulated by the NMs. A different study [ 71] used
PLGA nanoparticles to deliver recombinant human
EGF(rhEGF) in order to enhance full-thickness dia-
betic wound closure. Nanoparticles showed a sustained
release of rhEGF for 24 h. Sustained release of rhEGF
over time improved total healing effect via mouse fibro-
blast proliferation in in vivo model. A similar study with
PCL nanoparticles loaded with enoxaparin capped with
chitosan were investigated for wound-healing applica-
tion where particles were applied topically using the
gel ENOXA [3 2] . Such treatment displayed improved
wound healing in diabetic animals due to drug sta-
bility, and good skin penetration without any toxic

2596 Nanomedicine (Lond.) (2015) 10(16 )
Figure 2. Various nanomaterials showed beneficial effect in the different phases of wound healing. This figure divides nanomaterials
into four groups based on which phase of wound healing they effected /corrected. Most of the nanomaterials have shown an
enhanced wound healing by accelerating the proliferation (phase III) then inflammation (phase II) whereas very few nanomaterials
are known for help in hemostasis and remodeling. Interestingly, cerium oxide NPs have displayed the beneficial effects in all four
phases of wound healing.
NP: Nanoparticle.
57.1
32.7
6.1
4.1
Au
Au
Cu Fe2O3
Fe2O3
CeO2
CeO2
CeO2
CeO2
Ag
Ag
Nanoceria
Nanoceria
Nanoceria
Nanoceria
Polymer NPs
Polymer NPs
Copper NPs Iron oxide
NPs
Iron oxide NPs
Polymer NPs Solid lipid NPs
Solid lipid NPs
Silver NPs
Silver NPs
Ceramic NPs
Ceramic NPs
Ceramic NPs
Gold NPs
Gold NPs
Carbon-based NPs
Liposome
Liposome Dendrimers
Vesicles
Vesicles
Fullerenes
Self-assembling
elastin-like NPs
Micelle
Bioactive agent
Polymeric coating
Drug
KGF
Oligonucleotide
Plasmid DNA
Hg
NO
AT P
II Inflammation
I Hemostasis
IV Remodeling
III Proliferation
Wound-healing
phases
i
iii iv
ii
future science group
Review Kalashnikova, Das & Seal
effect. The study of hypericin (Hy)-loaded PCL-PEG
nanoparticles on infected in vivo cutaneous wounds
showed minimum expression of TNF. Modulations of
signal molecules production brought better epitheliali-
zation and collagen deposition [33] .
Other types of polymers, biodegradable poly(b-
amino esters) (PBAEs) and copolymers of maleic
acid were also widely investigated for gene delivery
and drug release systems for wound-healing applica-
tions [72 ,7 3]. Intradermal administration of the PBAEs

www.futuremedicine.com 2597
Figure 3. Wound model systems, incision models and methods of wound treatment. Model systems used for in vitro and in vivo
studies to explore the effects of nanomaterials on the wound-healing process are infographically presented. EpiDermFT (in vitro
model) is the epidermal full-thickness model, containing epidermis and dermis and represents close equivalent of skin but this model
is expensive and time consuming to prepare. Therefore, fibroblasts and keratinocytes isolated from mice or humans are very popular
as in vitro models. Mouse and rat models prevail among other animal models as mice and rats are readily available, easy to handle
and are cost effective. In this figure, we have also listed different incision models and administration methods used in literature for
wound-healing applications.
Cells
40.0
20.0
13.3
6.7
6.7
6.7
6.6
ECV-304
EpiDermFT
wounds model
Immortalized
keratinocytes
HEK cells
HUVEC Keratinocytes
Fibroblasts
Mouse
Chicken embryo
Rabbit
RatPig
27.6
58.6
3.4
3.4
6.9
Animals
Model systems
Methods of wound treatmentIncision models
4.5 mm 1.5–4 mm 0.5–8 mm 1.8–8 mm 1–2 flaps 1–1.5 mm
in length
4-6 mm
with ring stents
Spray
Intradermally
Intravenously
Topically
as a liquid
Topically as
an ointment
future science group
Nanomaterials for wound healing: scope & advancement Review
nanoparticles in a murine wound model was tested
in a recent study [74 ]. Sonic hedgehog gene (SHH)
loaded into the nanoparticles showed facilitated
angiogenesis and tissue regeneration by activating
angiogenic signaling pathways. Expressions of angio-
genic factors (two isoforms of VEGF and some che-
mokines such as SDF-1α were especially high in skin
tissue samples at early time points of wound healing.
The amine end-modified PBAEs did not show cyto-
toxic effects in vitro and was an effective vehicle to
deliver SHH in vivo [74 ]. PBAEs NMs, pH sensitive
system, correct pH at wound site that enhance anti-
bacterial defense.
Chitosan which is mentioned above is another nat-
urally occurring polysaccharide that has been exten-
sively researched for biomedical applications due to
its biocompatibility, biodegradability, mucoadhesivity
and anti-infection activity [34 ] . Chitosan nanoparticles
were shown to have significant bactericidal effects on
many different types of bacteria and no cytotoxic effect
on mouse fibroblast cells [35] . In this study, chitosan
particles were reported to modulate the inflamma-
tory response in human gingival fibroblasts. IL-1β-
stimulated prostaglandine E2 (PGE2) production
was inhibited by chitosan through the JNK (c-Jun
N-terminal kinases) pathway [ 65] .

2598 Nanomedicine (Lond.) (20 15) 10(16 ) future science group
Review Kalashnikova, Das & Seal
Table 1. Different nanomaterial samples studied for wound-healing application.
NM composition NM characteristics
(size, PdI, Z pot, EE)
Treatment parameters Model systems Benefits Ref.
Curcumin-PLGA 177 nm, 0.105, -23 mV,
89%
33 μg/μl, intradermally 6–7-week-old
RjHan:NMRI female
mice
Anti-inflammatory activity, improved re-
epithelialization and granulation tissue formation
[27]
rhEGF-PLGA 194 nm, 0.18, 86% 1 μg rhEGF, spray 8-week-old male
Sprague–Dawley rats
Stimulated fibroblasts proliferation, better tissue
repair at intermediate and advanced stages
[28]
Enoxaparin-PCL-chitosan 496 nm, 20 mV, 98% 2 mg/g gel ENOXA,
topically
6– 8-week-old male
Wistar rats
Improved wound healing via correction of
hemostasis and inflammation
[29]
Hy-PCL-PEG 50 nm, -9 mV, 75% 50 μl of 0.124 μM (HY)
topically
Female Wistar rats Downregulated TNF expression, upregulated VEGF
expression, better epithelialization, keratinization
and development of collagen fibers
[30]
SHH-PBAEs 238 nm, 21.3 mV 15.5 μg/μl,
intradermally
6-week-old female
athymic mice
Promoted angiogenesis and tissue regeneration [31]
KGF–ELP fusion protein 500 nm, 0.04 7.5 μg/μl fibrin gel
contained 0.036 nM
NPs
Genetically diabetic
male B6.BKS(D)
-Leprdb/J mice
Induced granulation, enhanced re-
epithelialization, prevented scar formation
[32]
PAM-RG4/minicircle
VEGF165 DNA complexes
115 nm, 23 mV 20 μg subcutaneously
at bilateral sites
8-week-old male
C57BL/ 6J mice
Diabetic wounds closure at rate similar to normal
ones by rapid collagen deposition, well- organized
dermal pattern and higher extent of mature blood
vessel formation
[33]
C60 modified with
hexa-dicarboxyl, tris-
dicarboxyl and gamma
(γ)- cyclodextrin
20 nm–1 um for CD-,
hexa-C60 and 100 –160
nm for tris-C60
25–100 μg/ml in
medium for 4 –24 h
HEK cells Altered cytokines (IL-1, -6, -8, TNF-α) response and
their release kinetics
[34 ]
MWCNs, GO, RGO 50– 60 nm COOH-,
60–90 nm NH2-MWNT,
-24 mV, +27 mV;
172 nm, 0.179, -56.5 mV
24– 48 h, 5–100 μg/ml NIH-3T3 and primary
human dermal
fibroblasts
Dose-dependent viability and wound closure [35, 36]
Clarithromycin-Ch-fatty
acids micelles
250–300 nm, <0.5,
39–44%
0.05–0.5 mg/ml Normal human dermal
fibroblasts
Induced cell proliferation [37]
Gll-Phl-Chol-α-gal
liposomes
Submicromic size,
100 mg/ml
10–100 mg NPs on the
pad of a dressing
3-month-old knockout
pigs for the 1,3GT
gene
Wound closure acceleration via rapid recruitment
of macrophages, effective cytokine production;
extensive angiogenesis, advanced collagen
deposition and granulation
[38 ,39]
db/db: Diabetes mice; ECM: Extracellular matrix ; EE: Encapsulation efciency; EGCG: Epigallocatechin gallate ; GO: Graphene oxide; HY: Hypericin; ICR: Institute for Cancer Research ; MWCN: Multiwalled
carbon nanotube; N /A: N ot available ; NM: Nanomaterial ; NMRI : Naval Medical Research Institute; NO: N itric oxide; PdI: Polydispersity index; Phl: Phospholipids; RGO: Reduced graphene oxide; ROS: Reac tive
oxygen species; TMSO: Tetramethylorthosilicate; T NF: Tumor necrosis factor; Z pot: Zeta potential; mod el systems include cellular in vitro systems used for c ytotoxicity test s.

www.futuremedicine.com 2599
future science group
Nanomaterials for wound healing: scope & advancement Review
Table 1. Different nanomaterial samples studied for wound-healing application (cont.).
NM composition NM characteristics
(size, PdI, Z pot, EE)
Treatment parameters Model systems Benefits Ref.
Lipoid–PEG /Ocdp–
curcumin and quercetin
liposomes
112–220 nm, -9 –13 mV,
0.23–0.37, 56–71%
20 μl for 3– 6 h,
topically daily for
3 days
New born pig skin
using Franz diffusion
cells; 5 –6-week-old
female Hsd :ICR(CD-1)
mice
Inhibited detrimental activity of ROS; MPO
accumulation and leukocyte infiltration;
reduced edema formation; increased fibroblasts
proliferation and production of collagen and
elastin
[40]
Phospholidip-PEG-Hb
vesicles
250 nm, 35 g Hb /dl 10 g/dl in 0.9% NaCl DDY mice Improved healing via enhanced oxygenation,
angiogenesis and vasculogenesis
[41]
ATP-phospholipid-
DOTAP, trehalose
vesicles
120 –160 nm N/A 8–10-week-old New
Zealand white rabbits
Rapid wound healing by correction of immune
response, speeding up granulation and re-
epithelialization
[42]
Liposomes-encapsulated
Hb
250 nm 2 ml (20% in saline)/
kg by tale’s intravenous
infusion at 2, 4 and
5 days
8-week-old Balb /c
mice
Collagen synthesis [43]
Solid lipids-morphine-
poloxamer 188 NPs
185–200 nm, 0.25,
100 ± 20%
50 μl of 125–250 μg /ml EpiDermFT wounds
models-human
full-thickness skin
equivalents
Promoted re-epithelialization [44]
rhEGF-Poloxamer-
Tween-80-Precirol ATO
5-Mygliol (SLN-rhEGF
and NLC-rhEGF)
332–357nm, ≈0.32,
-33–-35mV, 74–96%
10–20 μg in 20 μl of
vehicle (0.5% w/v
carboxymethylcellulose
in 0.9% w/v saline)
administered topically
twice a week
Balb/ C 3T3 A31
fibroblasts, human
foreskin fibroblasts,
human immortalized
keratinocytes (HaCaT);
8-week-old male db/
db and genetically
diabetic db /db mice
(BKS.Cg-m+/+Leprdb/J)
Speeded up wound healing via restoration of
inflammation and re-epithelialization
[45]
Chondroitin sulfate-
silver and acharan
sulfate-silver
5.8–6.2 nm, -16.9 mV 100 mg ointment daily 6-week-old male ICR
mice
Accelerated the deposition of granulation tissue
and collagen
[46]
Silver and
oligonucleotide
([5′-HS- (CH2)6-
TAATGCTGA AGG-3])-
silver
50 nm N/A Adult male Balb /cmice Improved the congestion, inflammatory cell
infiltration, fibroblast proliferation and new
collagen synthesis
[47]
db/db: Diabetes mice; ECM: Extracellular matrix ; EE: Encapsulation efciency; EGCG: Epigallocatechin gallate ; GO: Graphene oxide; HY: Hypericin; ICR: Institute for Cancer Research ; MWCN: Multiwalled
carbon nanotube; N /A: N ot available ; NM: Nanomaterial ; NMRI : Naval Medical Research Institute; NO: N itric oxide; PdI: Polydispersity index; Phl: Phospholipids; RGO: Reduced graphene oxide; ROS: Reac tive
oxygen species; TMSO: Tetramethylorthosilicate; T NF: Tumor necrosis factor; Z pot: Zeta potential; mod el systems include cellular in vitro systems used for c ytotoxicity test s.

2600 Nanomedicine (Lond.) (2015) 10(16 ) future science group
Review Kalashnikova, Das & Seal
NM composition NM characteristics
(size, PdI, Z pot, EE)
Treatment parameters Model systems Benefits Ref.
Bryonia laciniosa leaf
extract-silver
15 nm, -32.3 mV 0.09 mg NPs in gellun
gum gel daily for
14 days
Male Wistar rats, TE
353.Sk
Immunomodulation via cytokines (IL-6, -10)
level lowering; scar reduction by keratinocytes
migration, cell proliferation, ECM production,
reduced inflammation
[48]
BSA-Thrombin-γ-Fe2O320 nm 70 mg/ml in mix ture
containing fibrinogen
and a CaCl2 solution
Male Wistar rats Improvement of skin tensile strength adhesion,
reducing stitch-induced scarring
[49]
‘Metabolized’ Fe2O320– 40 nm 4 μl of 42.2 g /l in
distilled water
(pH 7–7.5)
Wistar rats Accelerated wound closure with esthetic scar
formation
[50]
Copper 33.8 –119nm 0.2 g copper-
methylcellulose-based
ointment
Female mice of the
SHK line
Regenerating activit y [51]
EGCG-alpha lipoic acid-
gold
3–5 nm 0.07 mg NPs/g of
ointment
Hs68 fibroblasts,
8-week-old male
BALB/c mice
Regulated the angiogenic effects, modulated
inflammation
[52]
EGCG-gold N/A Gas injection Wild-type and
streptozotocin-
induced diabetic mice
Increased VEGF and collagen I and III protein
expression
[53]
Chloroauric acid-gold 25–50 nm, -13.2 mV 5–20 μg /ml HUVECs and ECV-304,
chick embryo model
Proangiogenic activity: promoted cell migration,
new blood vessel formation
[54 ]
Cerium oxide 160 nm 1–2% daily 8-week-old female
Sprague–Dawley rats
Increased wound tensile strength amount of
collagen and hydrox yproline production
[55]
3–5 nm 0. 5 –10 μM, daily
topically
Human keratinocyte
cells, murine
dermal fibroblasts,
3–4-month-old male
C57BL/ 6 mice
Prevented infection, clearing debris, increased
density of blood vessels, enhance the proliferation
and migration of keratinocytes and fibroblasts
[56 , 57]
3–5 nm, -14.1–17.8 0 .1–1 μMHUVECs Modulated intracellular oxygen level, activated
HI F-1a
[58]
CaCl2-collagen-beta-
glycerol-phosphate
50–200 nm 100 μl with electrical
conductivity of 13
mS/cm, topically and
intravenous injection
8-week-old female
Balb/c mice
Decreased wound size via contracture by calcium
release calcium in pH-dependent manner
[59]
db/db: Diabetes mice; ECM: Extracellular matrix ; EE: Encapsulation efciency; EGCG: Epigallocatechin gallate ; GO: Graphene oxide; HY: Hypericin; ICR: Institute for Cancer Research ; MWCN: Multiwalled
carbon nanotube; N /A: N ot available ; NM: Nanomaterial ; NMRI : Naval Medical Research Institute; NO: N itric oxide; PdI: Polydispersity index; Phl: Phospholipids; RGO: Reduced graphene oxide; ROS: Reac tive
oxygen species; TMSO: Tetramethylorthosilicate; T NF: Tumor necrosis factor; Z pot: Zeta potential; mod el systems include cellular in vitro systems used for c ytotoxicity test s.
Table 1. Different nanomaterial samples studied for wound-healing application (cont.).

www.futuremedicine.com 2601
future science group
Nanomaterials for wound healing: scope & advancement Review
NM composition NM characteristics
(size, PdI, Z pot, EE)
Treatment parameters Model systems Benefits Ref.
NO-TMSO-PEG-chitosan N/A 5 mg, topically Human dermal
fibroblasts, 6–8-week-
old female Balb /C and
NOD.SCID/NCr mice
Stimulated migration and proliferation of
fibroblasts, and collagen type III expression,
increase vascularization, lessened inflammation,
upregulated expression of genes associated with
extracellular matrix formation and VEGF
[60,6 1]
Curcumin-TMSO-PEG-
chitosan
222 nm, 81.5% 7.5 mg/ml in coconut
oil, 50 μl topically daily
for 7 days
Keratinocy tes PAM212,
zebrafish embryos,
6– 8-week-old Balb /C
mice
Antimicrobial effect; accelerated wound closure
via well-formed granulation tissue, enhanced
collagen deposition, new vessel formation and re-
epithelialization
[62]
SiO215– 8 0 nm, 0.15 2–15 μl, 30–52% in
distilled water (pH
8.5–9) by a brush or a
micropipette on one
or two edges of the
wound
Wistar rat model Bleeding control; tissue repair; esthetic healing [5 0]
SiO2, Na2O, CaO and P2O530 – 60 nm, 1 μm Ointment (18 wt% of
bioactive glass powder
+ vaseline), topically
Specific pathogen-
free and chemical-
induced diabetic male
Sprague–Dawley rats
Promoted the proliferation of fibroblasts and
growth of granulation tissues, stimulated
production of two grow th factors, VEGF and FGF2
[62]
db/db: Diabetes mice; ECM: Extracellular matrix ; EE: Encapsulation efciency; EGCG: Epigallocatechin gallate ; GO: Graphene oxide; HY: Hypericin; ICR: Institute for Cancer Research ; MWCN: Multiwalled
carbon nanotube; N /A: N ot available ; NM: Nanomaterial ; NMRI : Naval Medical Research Institute; NO: N itric oxide; PdI: Polydispersity index; Phl: Phospholipids; RGO: Reduced graphene oxide; ROS: Reac tive
oxygen species; TMSO: Tetramethylorthosilicate; T NF: Tumor necrosis factor; Z pot: Zeta potential; mod el systems include cellular in vitro systems used for c ytotoxicity test s.
Table 1. Different nanomaterial samples studied for wound-healing application (cont.).

2602 Nanomedicine (Lond.) (2015) 10(16 ) future science group
Review Kalashnikova, Das & Seal
The N-acetyl glucosamine from chitosan is a com-
ponent of dermal tissue as well as elastin. Elastin is a
protein that plays a role in structural, mechanical and
cell signaling [3 6] . A recent study of synthesized chime-
ric nanoparticles formed via spontaneous self-assem-
bling of elastin-like peptides (ELP) [3 7] has revealed
its perspective for wound healing. ELP particles, KGF
and ELP particles with KGF loaded (KGF–ELP) in
fibrin gel and fibrin gel itself were tested and compared
both in vitro and in vivo models. ELPs itself increased
almost fivefold in fibroblast proliferation [3 7] . One-
time administration of ELP-KGF particles improved
re-epithelialization and granulation within wound sites
of diabetic mice in comparison to the controls.
Dendrimers, highly branched polymers in particu-
lar polyamidoamine (PAMAM) have been successfully
used for cellular delivery of plasmid DNA, forming a
stable complex by limiting its degradation. For exam-
ple, arginine-grafted cationic dendrimer was tested for
wound healing in diabetic and normal mice as a vehicle
to deliver minicircle plasmid DNA encoding VEGF.
This polycomplex (PAM-RG4) provided rapid prolif-
erating basal cells and collagen deposition. Further-
more, less immature blood vessel formation resulted in
diabetic wound recovery comparable to wound heal-
ing for normal mice [38] . Dendrimers have structure
with internal cavities and surface channels which are
favorable for accommodation of small molecules. This
unique feature of dendrimers to carry high amount
of drugs can be used for treatment of hard-to-heal
wounds required medicine administration. In addition
to the delivery of plasmid, research was also conducted
toward development of oligonucleotide delivery nano-
vehicles for wound-healing application. Sirnaomics,
Inc. has been working on developing the effective
formulation contained siRNA, targeting for TGFβ1
and Cox-2 (cyclooxygenase-2), encapsulated into HK
polymer nanoparticles. The nanoparticles in methyl-
cellulose formulations demonstrated pain reduction
with antifungi activity, wound-healing acceleration
and minimization of scar formation [33]. Other, non-
coding RNAs known to regulate inflammation (146a),
proliferation of cells (21, 15b, 222/221) and remodel-
ing (29a) phases can be tested for their efficacy to heal
wound faster [3 9– 41 ,4 3].
Carbon-based NM therapy
Carbon NMs, including fullerenes, carbon nanohorns
and carbon nanotubes and graphene have gained
interest in nanomedicine due to their versatile uses
in advanced imaging, tissue regeneration and drug
or gene delivery [4 2, 44] although their biocompatibil-
ity remained controversial [4 2] . Fullerenes and carbon
nanotubes displayed positive results in wound healing
via correcting inflammatory and proliferative phases.
Since fullerenes are superpowerful antioxidants, they
are capable of scavenging and detoxifying ROS and
reactive nitrogen species [4 4] . Fullerenes can be func-
tionalized to avoid aggregation, and alter their solubil-
ity and toxicity using hexa-dicarboxyl, tris-dicarboxyl
and gamma (γ)-cyclodextrin (CD) [45] . Modified
fullerenes were explored to study immune cell response s
in keratinocytes. Pro-inflammatory cytokines (IL-1, -6
and -8) expression and release kinetics were analyzed.
Cytokines TNF-β, GROβ (the IL-8-related chemo-
tactic cytokine), and RANTES (CCL5/regulated on
activation, normal T-cell expressed and secreted) level
after exposure to different fullerene derivates which
regulate keratinocyte proliferation, differentiation,
migration, apoptosis and angiogenesis in cutaneous
wound-healing models were also evaluated. The release
of the cytokines was influenced by functionalization of
the fullerene’s surface [45] . For example, tris-C60 sig-
nificantly reduced inflammatory cytokine secretions
in a dose/time-dependent manner, whereas CD-C60
led to an increase in IL-6 and IL-8 secretions. The
nature of fullerenes altered cell cycle as well as the pro-
liferation capacity of cells [45] . The behavior aspects of
other carbon materials such as graphene (GO, RGO)
and carbon nanotubes were tested on murine fibro-
blasts [75 ,76] . The cells were exposed to a layer made of
multiwalled carbon nanotubes (MWCNs), function-
alized MWCNs, graphene oxide and reduced graphene
oxide for 24–48 h. This was done to study cell viabil-
ity, morphology, adhesion, spreading and proliferation
patterns. No cytotoxic effects or difference in the cell’s
proliferation and adhesion were observed for various
substrates. However, cells were spread broader on the
substrates contained MWCNs. The substrates with a
high water contact angle demonstrated less focal adhe-
sions per cell, whereas gene transfection was better on
the relatively less rough substrates [76] .
Lipids contained NM (micelles, vesicles and
liposomes) therapy
Chitosan fatty acids micelles were suggested as prospec-
tive carriers to deliver hydrophobic drugs in the cur-
ing of complicated wounds [77] . Clarithromycin-loaded
(clarithromycin-Ch-fatty acids) micelles were fabricated
via self-assembling of chitosan and mixture of oleic and
linoleic acids. The micelles were characterized for their
size and polydispersity, cytotoxicity on normal human
dermal fibroblasts. Moreover, their mucoadhesive prop-
erties, and drug loading capacity were also investigated.
In fact, the micelles displayed good biocompatibility,
ability to induce cell proliferation, and about 20-times
higher clarithromycin loading capacity compared with
saturated solution in water [77] .

www.futuremedicine.com 2603
future science group
Nanomaterials for wound healing: scope & advancement Review
A very interesting approach of accelerating wound
closure was invented using liposomes [7 8,79] . Submicro-
scopic liposomes (Gll-Phl-Chol-α-gal) were prepared
from mixtures of lipids, extracted from rabbit red
blood cell membranes and loaded with α-gal epitopes.
Carbohydrate antigen, α-gal epitope (Galα1–3Galβ1–
4GlcNAc-R), binds to the anti-Gal antibody within a
wound and activates the cascade of the compliments,
which cleave chemotactic factors, C5a and C3a. Local
increasing concentrations of chemotactic factors in a
wound site induced rapid recruitment of macrophages
followed by their migration into the wound site [78 ,79] .
Next, α-Gal nanoparticles were bound to the receptors
on the membranes of infiltrated macrophages and acti-
vated the secretion of prohealing cytokines that accel-
erated healing of the wound. Wounds in pigs that were
treated topically with nanoparticles by thin fluidic film
showed accelerated rate of wound closure by more than
25% [7 8] .
Liposomes (lipoid-PEG/Ocdp-curcumin and quer-
cetin liposomes) are a mixture of soybean phospholip-
ids, triglycerides, fatty acids and contained PEG and/or
octyl-decyl polyglucoside and loaded with curcumin and
quercetin were stud ied to treat in vitro and in vivo models
of full-thickness skin defects [46] . The used phytodrugs
possessing antioxidant and anti-inflammatory proper-
ties were able to prevent skin ulceration and enhance
early regeneration of wounds. Several bionanovesicular
formulations facilitate the drugs delivery and allowed
effective modulation in inflammation by neutralizing
detrimental activity of ROS, preventing MPO accu-
mulation and leukocyte infiltration. In another study,
hemoglobin-loaded phospholipid bilayer vesicles coated
with polyethylene glycol (HbVs) enhanced the oxy-
genation of ischemic cutaneous wounds [ 47, 4 8]. At the
first postsurgery day, oxygen saturation reached 15%
higher level in ischemic wounds after treating wound
with HbVs. Tissue survival was improved by 24% and
wound-healing rate was accelerated twofold on the 6th
postoperation day. The immunohistochemical assess-
ments revealed higher capillary density and higher
endothelial nitric oxide synthase 3 (eNOS) expression
in the wounds exposed to HbVs. Another study com-
pared hemoglobin (Hb) encapsulated nanocarrier with
red blood cells for cutaneous wounds healing [47] . The
Hb-liposomes prevented ischemic wound formation by
suppressing inflammation and accelerating granulation.
However, there were no supporting data for new blood
vessel regeneration with treatment of liposomes in this
study [48] . Skin defects were significantly (30%) reduced
under the Hb-liposomes infusion via rapid fibroblast
proliferation and collagen deposition [47] .
In another interesting approach, adenosine triphos-
phate (ATP)-vesicles were synthesized and tested for
wound-healing application where vesicles were applied
using nonionic cream. ATP-vesicles were constructed
from phospholipids, DOTAP (liposomal transfection
reagent) and trehalose. They were mixed with a non-
ionic vanishing cream (Dermovan) for application. As
expected, ATP-vesicle was shown to provide an energy
source for cell survival, enhanced granulation and re-
epithelialization in rabbit’s diabetic wounds, for both
nonischemic and ischemic models [80]. These vesicles
were able to correct immune cells response which is
delayed in diabetic wounds by stimulating the infiltra-
tion of neutrophils, lymphocytes and macrophages at
early stage of postwounding. The significant accelera-
tion of wound-healing rate was observed in compari-
son to the controls (saline solution, empty vesicles, Mg-
ATP, cream) for nonischemic (16.5%) and ischemic
wounds (20.7%). These results indicate that transfec-
tion agent can be also used for efficient delivery of other
molecules having wound-healing capabilities such as
drugs, oligonucleotides and microRNA, among others.
As mentioned earlier, lipid-based nanoparticles were
able to promote re-epithelialization as well as solid
lipid NPs (SLNPs). For example, SLNPs with encap-
sulated morphine, were reported to control pain and
accelerated keratinocyte migration, proliferation and
differentiation [49] . Two other formulations, SLNPs
and nanostructured lipid carries (NLCs) were loaded
with rhEGF which demonstrated effectiveness in
enhanced wound closure at topical administration to
diabetic mice. RhEGFs released from the nanoparti-
cles during 72 h of treatment were bioactive and signif-
icantly induced cell proliferation in vitro (two types of
fibroblasts and keratinocytes) compared with control
nanoparticles. Similar cellular uptake and subcellular
distribution were detected for both formulations. A
reduction in polymorphonuclear leukocytes, domina-
tion of damaged tissues regeneration and formation of
new connective tissue and blood vessels were exhibited
by the nanoformulations. Wounds treated with rhEGF
(free or encapsulated) revealed approximately 13%
faster wound healing than the control groups (empty
nanoparticles or vehicle) with new epithelium covering
more than 50% of the wound [5 0] . The approach of
delivering growth factor locally to the wound site using
lipid particles works very well as it was discussed above
in terms of polymer nanoparticles.
Metallic & metal oxide nanoparticle therapy
Different types of metal or metal oxide nanopartilcles
were analyzed for their wound-healing application, sil-
ver nanoparticles is one of them. Silver nanoparticles
(AgNPs) as well as silver have proven to exhibit antimi-
crobial activity against a broad range of microbes includ-
ing fungi, different types of bacteria, yeast and even

2604 Nanomedicine (Lond.) (2015) 10(16 ) future science group
Review Kalashnikova, Das & Seal
viruses [51] , reducing or preventing wound infection. The
antibacterial activity of AgNPs showed correlations with
physical properties such as shape and size of nanopar-
ticles [81] . For example, trihedral-shaped particles
showed higher antimicrobial activity than spherical and
rod-shaped particles [81] . Silver has anti-inflammatory
properties [8 2] and minimize ROS production depend-
ing on size and concentration of nanoparticles [83].
AgNPs were also reported to improve tensile properties
of repaired skin by influencing collagen alignment [5 2] .
Silver nanoparticles modified with chondroitin sul-
fate and acharan sulfate were recently demonstrated to
stimulate wound recovery, and accelerate collagen depo-
sition and new tissue formation in the wound area [54 ] .
A recent study compared bare silver nanoparticles and
nanoparticles coated with oligonucleotide ([5′-HS-
(CH2)6-TAATGCTGAAGG-3]) (20–200 nm) in
a full-thickness skin wounds model of 4.5-mm diam-
eter [53 ] . The idea of nanoparticles surface modification
was to improve the biocompatibility of nanoparticles by
delaying the release of silver ions and minimizing their
toxic effect on tissues. Surface functionalized nanopar-
ticles regulated inflammatory response and enhanced
the proliferative phase of wound healing via rapid fibro-
blasts and collagen deposition [53] . Green synthesis of
AgNPs using Bryonia laciniosa leaf extract improved
the nanoparticles cytocompatibility and efficacy toward
wound healing in comparison with marketed cream with
silver sulfadiazine [84] . Results showed an acceleration of
rapid wound epithelialization and wound closure. Inter-
estingly, scarless healing was reported by modulating
pro-inflammatory cytokines (IL-6 and IL-10).
Other than silver, iron oxide was also explored for
wound-healing applications [55] . Thrombin-conjugated
γ-Fe2O3 nanoparticles accelerated the healing of inci-
sional wounds significantly via relative improvement
of skin tensile strength and reducing stitch-induced
scarring [5 6] . ‘Metabolizable’ iron oxide nanoparticles
purchased from Alfa Aeser and stabilized by citric acid,
peptized with NH4OH were also tested as a new adhe-
sive/suturing material for dorsal skin wound repair
for the organs which provided fast hemostasis without
bleeding syndrome and inflammation [57] . Recently,
copper nanoparticles have been shown to induce
pro-inflammatory mediators that increase microves-
sel formation [5 8] . In this study, copper nanoparticles
with methylcellulose-based ointment were applied to
a 60 mm2 full-thickness wound of mice skin [8 5] . The
authors have also investigated the effect of nanoparticle
size and crystalline copper content on wound healing.
The fastest primary adhesion was found for nanopar-
ticles with the biggest sizes (100–119 nm), whereas
the highest regenerating activity (51.7%) was detected
for nanoparticles (119 nm) with the lowest crystalline
copper content (0.5%). Two other samples containing
96 and 94% crystalline copper also accelerated wound
healing by 44.8 and 37.9%, respectively.
Application of gold nanoparticles (AuNPs) in the
field of diagnostic and imaging tool, antitumor agent,
drug delivery system, photothermal and photodynamic
therapies was explored [59, 86]. It is interesting to men-
tion that gold nanoparticles, in combination with
other drugs or simply alone have also been tested for
wound-healing capabilities. The combination of AuNP
and antioxidants epigallocatechin gallate (EGCG) and
alpha lipoic acid were able to modulate two phases of
wound healing: inflammatory and angiogenesis. These
occur at the molecular level in wounds of diabetic mice.
The proangiogenic properties in vitro and in vivo wound
models were revealed for biosynthesized gold nanopar-
ticles (b-Au-HP) [87] . Antioxidant activity of AuNPs
occurs by controlling ROS generations (hydrogen per-
oxide and superoxide anion) [60] . Exposure of endothe-
lial cells (HUVECs, ECV-304) to b-Au-HP resulted
in induced cell proliferation with increased mitosis in
a time-dependent manner. Moreover, treatment of the
chick embryo model with AuNPs promoted new blood
vessel formation in a dose-dependent fashion and time-
dependent migration of HUVECs cells into the wound
area. Another group [61] used gas-injection by the GNT
GoldMed™ Liquid Drug Delivery System to treat dia-
betic wounds with the mixture of EGCG and AuNPs.
Such formulation increased VEGF and collagen I and
III protein expression in the wound area while speeding
the rate of murine wound healing.
Metals from lanthanide group and its oxide or
hydroxide revealed their regenerative potential.
OmegaGenesis attained improved angiogenesis using
europium hydroxide nanorods [62] to aid in the heal-
ing of a variety of wound types. The liquid suspension
of nanorods was formulated using a cream or gel to
enhance healing. The nanorods suspension can be uti-
lized in combination with pain relief and anti-infective
to enhance the wound-healing process. Another rare
earth oxide nanoparticle, cerium oxide nanoparticle
(160 nm) was reported to improve wound healing
activity in in vivo model [88] by inducing an amount
of hydroxylproline content and collagen production,
which increased wound tensile strength and reduced
wound closure time. Other groups [89, 90] investigated
nanoceria’s (cerium oxide nanoparticles) effect on
wounds using 10 μM nanoceria suspension with par-
ticles of size <20 nm. Nanoceria showed an increase in
speed of cutaneous wound healing in mice models. The
migration of major skin forming cells was enhanced
in a concentration-dependent manner [8 9– 91] . A rapid
infiltration of inflammatory cells into the wound area
and significantly greater density of blood vessels were

www.futuremedicine.com 2605
future science group
Nanomaterials for wound healing: scope & advancement Review
reported for nanoceria-treated mice, as compared with
the control [90] . Moreover, it has been shown that
nanoceria are able to induce proangiogenesis by stabi-
lizing HIF-1a expression and altering gene regulation
via modulation of intracellular oxygen level [91].
As mentioned, reports on metal/metal oxide na nopar-
ticles have revealed potential in the field of wound care,
including reduction/prevention of infection, induced
migration of cells needed for angiogenesis or faster
healing and increase in the strength of the healed skin.
However, the use of metal/metal oxide nanoparticles in
medicine brings concerns about the safety aspect of the
metal/metal oxide nanoparticles to environment and
living systems which are not clear. A recent publication
warns about topical treatment of burn and wounds, and
reported that toxicity has correlation with size of the
AgNPs [92] . Viability of normal human dermal fibro-
blasts had strong correlation with size of the nanoparti-
cles. Small AgNPs (4.7 nm) were much more cytotoxic
than large NMs (42 nm). Moreover, small nanopar-
ticles induced oxidative stress and depleted glutathione
level [9 2] . Toxicity of different nanoparticles including
titanium dioxide, zinc oxide, magnesium oxide, silver
and gold was tested on mice skin cells in comparison
with triglyceride-coated nanoparticles [86 ,9 3]. Coating
increased the nanoparticle’s biocompatibility, cell meta-
bolic activity, ATP level and decreased ROS generation.
Interestingly, it is reported that metal nanoparticles
were more toxic than metal oxide nanoparticles [86] .
In addition to cytotoxicity, biodistribution and rate of
NMs clearance should also be evaluated.
Ceramic NM therapy
There are several examples of the use of ceramic mate-
rial contained silica, and its derivates, calcium salts and
hydroxyapatite in the form of nanoparticles for wound
healing. Collagen-coated calcium-based nanoparticles
that were synthesized using CaCl2 with beta-glycerol-
phosphate had the potential to modulate calcium
homeostasis and the pH of milieu which accelerates
skin wound healing [9 4] . It is proven from literature,
that even a small change in pH may promote or inhibit
bacteria growth, and enzymes prevalence, and alter
the oxygen supply [9 5] . Nevertheless, the authors con-
cluded that decreasing the open wound size occurred
via contracture [94].
Nitric oxide (NO)-releasing nanoparticles that were
synthesized using a mixture of tetramethyl orthosili-
cate (TMOS), polyethylene glycol, chitosan, glucose
and sodium nitrite. These nanoformulations promoted
angiogenesis and enhanced vascularization. NO stim-
ulated migration and proliferation of fibroblasts, and
collagen type III expression in the affected area that
increased the rate and degree of granulation [96] . In
another study, these NMs showed enhanced vascu-
larization, well-organized tissue deposition, reduced
inflammation and improved wound closure [97] . Simi-
larly, TMSO-based nanosuspension with curcumin
encapsulation, demonstrated antimicrobial effects
toward gram-negative pathogens and an accelerated
wound-healing process [98] . There were four appro-
priate controls used in this study: curcumin, bare
nanoparticles, vehicle and silver sulfadiazine. There
were delays in wound healing observed for each con-
trol. Significant impacts of curcumin-TMSO NMs on
wound closures were observed via well-organized gran-
ulation, enhanced collagen deposition and maturity
and increased neovascularization within the wound
site. It has been reported that NMs accelerated wound
closure by about 34% in comparison to the control [98] .
Silica nanoparticles (SiO2 NPs) have been sug-
gested as innovative suturing and adhesive alternative
to Dermabond (2-octyl cyano-acrylate) and Ethicon
4/0 [57] . SiO2 NPs synthesized by the Stober method
and purchased from Aldrich (silica Ludox TM-50),
were tested for nanobridging of full-thickness dorsal
skin and hepatic injury in the Wistar rat model [57 ] .
These NPs in distilled water or as a powder were
deposited into the bleeding area and two edges of
the wound were manually kept together for a while.
Hemostasis occurred in 1 min and thin granulation
tissue was observed on day 3 postsurgery of the skin.
In the case of hepactectomy, the PVA membrane with
SiO2 powder was placed on the bleeding section of the
hepatic lobe. Nanobridging on the rat’s beating heart
was also performed using silica Ludox TM-50 which
was brushed on the heart surface as an adhesive for
3D-porous polysaccharide biodegradable hydrogel.
These studies have shown that silica nanoparticles as
nanobridging material have a lot of potential for liver,
spleen, kidney, heart and lung surgeries. This study
did not test the toxicity of the silica NM. Toxicological
data of the silica material would complete the study.
Bioactive glass is another material which has been
commercialized for their dental or bone regenerative
applications. It was reported that healing of the cuta-
neous wounds in normal and diabetes-impaired rats
can be accelerated by bioactive glasses. For instance,
bioactive glass samples [9 9] were able to promote the
proliferation of fibroblasts and growth of granulation
tissue, and stimulated the production of growth fac-
tors such as VEGF and FGF2. Rate of wound heal-
ing depended on the composition of bioactive glass.
Commonly, samples were based on SiO2, Na2O, CaO
and P2O5 with irregular bulks of 60 nm spheres, and
relatively dispersible nanoparticles in surface (about
30 nm). Every sample was mixed with melted Vaselin
to obtain an ointment and can be applied topically [99].

2606 Nanomedicine (Lond.) (2015) 10(16 ) future science group
Review Kalashnikova, Das & Seal
Scaffolds with NM-embedded therapy
In a series of papers about the development and appli-
cations of functionalized biomaterials as bedding, scaf-
folds, gel and dressings with embedded NMs of various
kinds are listed. This direction represents a combina-
tion of conventional (scaffold, dressing) and advanced
therapy (NMs). Several interesting and recent exam-
ples are discussed in this section and schematically
presented in Figure 4.
A recent study investigated some of these simple and
combined approaches [10 0] . The pad-dry-cure tech-
nique, cotton fabrics with loaded suspension of pow-
dered silver nanoparticles (12–22 nm, 0.163, −28 mV)
showed great potential for healing similarly to the con-
trolled cream (Dermazin) [10 0 ] . In an alternative study,
a flexible polyethylene cloth with distributed nanocrys-
talline silver particles was tested in both in vitro and
in vivo wound models [1 01] . No signs of toxicity and
cells deaths were observed in the healed skin samples
of patient’s biopsies, although the authors noticed tem-
porary reduction of mitochondrial functionality. Inclu-
sion of AgNPs into the dressing led to the fast regen-
eration of cutaneous layer in vivo. AgNPs (10–30 nm)
deposited onto bacterial cellulose nanofiber arranged
in a form of network has displayed 99% reduction of
Escherichia coli, Staphylococcus aureus and Pseudomo-
nas aeruginosa growth via slow Ag+ release from the
composite. It also allowed attachment and growth of
epidermal cells within the wound site [10 2] . In another
study, authors tested a new cationic biopolymer guar
gum alkylamine with AgNPs [1 03 ] . The enhanced
wound closure was promoted via hydration of wound
surface and induction of the proliferative phase of
wound healing [10 3] . A similar combined strategy was
approved for preclinical study of fibrous mats/scaffolds
as a wound dressing [10 4 ] . The mat produced via elec-
trospinning using PVA and chitosan oligosaccharides
with loaded AgNPs (15–22 nm) displayed no toxicity
and antibacterial activity toward E. coli and S. aureus
within the wound site [10 4] . Covalently cross-linked
alginate fibrous hydrogel promoted the regeneration
process by promotion of fibroblast migration to the
wound area and reduction of the inflammatory phase.
This material improved the quality as well as rate of the
healing process [1 05] .
The wound healing potential of chitosan-copper
and zinc nanoparticle’s (dispersion of 30–40 and
30–70 nm) composites was evaluated [10 6 ] in adult rats
in another study. Antibacterial and anti-inflammatory
effects were observed in the treated group. Another
investigation [10 7] using similar nanocomposites based
on chitosan and copper nanoparticles (50 nm) reported
increases in VEGF, TGF-β1 and IL-10 expression. In
conclusion, facilitation of all components of the pro-
liferative phase of the wound healing process was
revealed [10 7] . Another study investigated chitosan
nano-dressing composed pectin and TiO2 nanopar-
ticles (20–40 nm) [3 4] which provided excellent anti-
microbial properties with good biocompatibility and
a control level of moisture. These composite materials
were suggested for wound-healing applications based
on their demonstrated healing efficiency in vivo.
Surface-modified magnetite (Fe3O4@C16) nanopar-
ticles with vegetal origin, eugenol and limonene, were
used to prepare wound dressings with both microbi-
cidal and antiadherence properties, which are sig-
nificant for wound regeneration [10 8] . Similar to this
study, the incorporation of gentamicin-loaded ZnO
nanoparticles (polyhedral-shaped particles, 15 nm) in
chitosan three-component gel, was offered for wound
dressing [1 09 ] . Incorporation of nanopowder with
antibiotics into a chitosan gel matrix provided a slow
release rate of the drug. Synergic effects of antibacte-
rial activity and combinations of beneficial features for
wound-healing application enhanced the growth inhi-
bition for S. aureus and for P. aeruginosa, as compared
with the gentamicin control. The composite may also
serve as a water source to restore a humid environment
within the wound interface while providing a cooling
sensation and soothing effect [10 9] .
As we can see, plenty of researchers were interested
in the development of dressings and scaffolds with
embedded metallic nanoparticles based on silver, cop-
per, zinc and magnetite, whereas only a few publica-
tions have discussed scaffolds embedded with polymer
NMs in wound-healing application. Biomimetic skin
substitutes comprised poly(L-lactic acid) scaffold with
immobilized type I collagen. Scaffolds were embedded
with PCL nanoparticles loaded with indomethacin or
polyester urethane nanoparticles (218 and 196 nm,
respectively) and had a positive effect on cellular
growth as well as tissue regeneration which potentially
enhanced healing response [11 0] .
A promising therapeutic platform capable of sus-
taining release and intracellular delivery of siRNA
has been presented in a recent study [111] which used a
biodegradable and porous polyurethane scaffold (com-
posed of a polyol component that is 60% PCL, 30%
poly(glycolide), 10% poly(d, l-lactide) and a harden-
ing component-lysine triisocyanate). This formula-
tion and delivery of siRNA were able to knock down
the overexpressed pro-inflammatory genes in chronic
nonhealing skin wounds.
Chitosan-poly(ethylene oxide) nanofibrous electros-
pun scaffold with embedded PLGA nanoparticles has
been evaluated in vivo for wound healing [11 2] . PDGF
and VEGF encapsulated PLGA nanoparticles were
also tested for wound-healing applications [11 2] .

www.futuremedicine.com 2607
Figure 4. Examples of scaffolds with embedded nanomaterials for wound-healing treatment. Wound healing
scaffold represents gel-type, polymeric, fibrous or spongiform 3D matrix with loaded substance exhibiting wound-
healing property and with embedded nanomaterial.
NP: Nanoparticle.
Chitosan-poly
(ethylene oxide)
electrospun scaffold
Polymer NPs Polymer NPs
Polymer NPs
Polyurethane
scaffold
Solid lipid NPs
Silver NPs
Silver NPs
Silver NPs
Ag
Ag
Ag
ZnO
Poly (L-lactic acid)
scaffold
Flexible
polyethylene cloth
Cotton fabrics
Crosslinked
alginate gel
Zinc oxide NPs
Chitosan gel
Poloxamer gel Carbon nanobrushes
Carbomer hydrogel
Collagen
siRNA
Drug
VEGF
Bioactive agent
future science group
Nanomaterials for wound healing: scope & advancement Review
Few studies also explored carbon nanocomposite
and lipid nanoparticles embedded scaffolds for wound-
healing applications. Carbon nanobrushes embedded
in a biocompatible poloxamer gel was able to enhance
growth capabilities, stimulate wound closure and
repair injured tissue [11 3] . Astragaloside IV, possesses
anti-inflammatory activity and was able to accelerate
wound healing, and reduce scars. Astragaloside IV-
enriched solid lipid nanoparticles incorporated in car-
bomer hydrogel was examined for their wound-healing
abilities using in vitro (immortalized human fibroblast
and keratinocyte cell lines) and in vivo (rat full skin
excision) models. Such dressing improved the migra-
tion and proliferation of keratinocytes, strengthened

2608 Nanomedicine (Lond.) (2015 ) 1 0(16) future science group
Review Kalashnikova, Das & Seal
Executive summary
Advantages over conventional materials
• Nanomaterials (NMs) therapy seemed to be more beneficial than conventional therapy in wound care. NMs
embedded scaffolds are the future of wound care products.
• NMs are able to modify one or more wound-healing phases.
Toxicity & mechanism of action
• Cyto- and gene-toxicity of NMs must be taken into careful consideration before applying any NM for therapy.
• Signaling pathways of wound healing should be investigated in details and be distinguished for each wound-
healing phase in the presence or absence of NMs.
wound healing and inhibited scar formation in vivo by
speeding up wound closure [11 4] .
Conclusion
Reviewed herein are potential applications of NM-
based approaches in the area of cutaneous wound care
for the last 5 years. This overview reveals the benefits
of using NMs in wound healing. It is important to
note that any outcome of NM therapeutics depends on
the NM formulation, doses and methods of applica-
tion. Beneficial effects of different NMs/NM embed-
ded scaffolds for wound-healing applications have
been reported; however, the molecular mechanisms/
signaling pathway of NM action on wounds were not
clearly understood. Better understanding of the signal-
ing pathway will elucidate the actions of NMs on the
wounds, and will help to establish nanotechnology-
based wound-healing therapy. Understanding the cel-
lular response and analysis of cell signaling pathways
involved in wound-healing with varying physicochem-
ical features of NMs may open up new routes for novel
nanotherapeutics. As NMs are highly active compared
with its bulk, toxicity of NMs must be taken into con-
sideration in every case before its usage in wound care
products.
Future perspective
Conventional therapy in wound-healing care is dress-
ing based. Traditional dressings are intended to pro-
vide wound cover, bleeding arrest, fluid adsorption,
moistening or/and drying, infection protection and
dead tissue removal. NMs, due to their unique prop-
erties open a new array of wound-healing products.
NMs can modify each phase of wound healing as they
possess antibacterial and anti-inflammatory activities,
proangiogenic and proliferative properties. NMs are
able to correct expression level of some important pro-
teins and signal molecules to enhance wound healing.
Thus, NMs or the combination of materials at both
micro and nanoscales, may become beneficial enough
to overcome most of the challenges that exist in wound
care management. Distinguishing the functions of con-
ventional materials and novel NMs in wound-healing
therapy may lead to successes in managing complicated
wounds, such as chronic and ischemic ulcers by a com-
bination of nanomicro hybrid materials. Development
of novel biocompatible and biodegradable NMs, which
are able to correct all phases of wound healing, can be a
future goal for researchers working in this area.
Acknowledgements
The authors would like to thank O Krokhicheva and S Rudik
who mad e all of the illustrati ons for this rev iew. The autho rs are
very thankful to S Heller who helped in manuscript preparation.
Financial & competing interests disclosure
Th e au th ors ack no wledg e Nem ou rs and Flor id a High Tech cor-
ridor for funding support. The authors have no other relevant
afliations or nancial involvement with any organization or
entity with a nancial interest in or nancial conict with the
subject matter or materials discussed in the manuscript apart
from those disclosed.
No writing assistance was utilized in the production of this
manuscript.
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