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Green Nanotechnology from Cumin Phytochemicals: Generation
of Biocompatible Gold Nanoparticles
Kavita Kattia, Nripen Chandaa, Ravi Shuklaa, Ajit Zambrea, Thilakavathi Suibramaniana,
Rajesh R. Kulkarnia, Raghuraman Kannana,b,*, and Kattesh V. Kattia,b,*
a Departments of Radiology, Physics, Bio-medical Sciences and Nuclear Science and
Engineering Institute, University of Missouri, Columbia, MO 65212, USA
b Greennano Company, Alton Building, Room 228-229, Columbia, MO 65212, USA
Introduction
Recent developments in nanotechnology have witnessed the rapidly evolving power of this
interdisciplinary field with myriad of applications in medical sciences, in the development of
smart electronic materials, in alternative energy generation, in environmental restoration and
in various allied fields1–14. All of these advancements require the production of a large
variety of nanoparticles, including both the metallic and non metallic, in large scales. As the
nanorevolution continues to unfold, it is imperative that the manufacturing processes, for
both nanoparticle production and nanoparticle embedded finished products, incorporate
environmentally sound and non polluting technologies. Several of the currently used
nanoparticle production processes utilize toxic chemicals either in the form of reducing
agents to reduce various metal salts to their corresponding nanoparticles or as stabilizing
agents to stop nanoparticles from agglomeration15–17. For example, hydrazine and sodium
borohydride are powerful reducing agents which are currently used in the reduction
reactions of gold (and metal compounds) to produce gold and various metallic
nanoparticles15,16. Both hydrazine and sodium borohydride are highly toxic to living
organism and the environment. If certain chemical ingredients used in the nanoparticles
production processes are non toxic, the chemical trail that is left behind in the course of
production of such chemicals may lead to environmental pollution upon sustained use of
such processes for a long time. If alternative processes are not available, due care must be
exercised in proper handling and disposal of toxic chemicals and various reducing and
stabilizing agents in manufacturing processes.
It is important to recognize that various herbs, spices and plant sources occlude powerful
antioxidants as photochemical constituents in seeds, stems, fruits and in leaves.18–22 These
naturally occurring antioxidants are already within the human food chain and have been
proven to be non toxic to living organisms and to the environment for thousands of years.
23–26 The utility of plant based phytochemicals in the overall synthesis and architecture of
nanoparticles and various nanoparticle embedded products is highly attractive as it brings an
important symbiosis between natural/plant sciences and nanotechnology.27–29 This
connection between plant sciences and nanotechnology provides an inherently green
approach to nanotechnology referred to as green nanotechnology.30–32 We have recently
reported the application of phytochemicals available within Soy and Tea as dual reducing
and stabilizing agents for the synthesis of gold nanoparticles.33, 34 We herein report the
utility of phytochemicals occluded within cumin as reducing agents for the reduction of gold
salts to the corresponding gold nanoparticles. Phytochemical constitutents of cumin include:
Fax: (+1) 573-884-5679. kannanr@health.missouri.edu, kattik@health.missouri.edu.
NIH Public Access
Author Manuscript
Int J Green Nanotechnol Biomed
. Author manuscript; available in PMC 2009 November 03.
Published in final edited form as:
Int J Green Nanotechnol Biomed
. 2009 January 1; 1(1): B39–B52. doi:10.1080/19430850902931599.
NIH-PA Author Manuscript NIH-PA Author Manuscript NIH-PA Author Manuscript
volatile oils, fats, numerous alcohols and aldehydes.35–41 The volatile oil has been
characterized as primarily aldehydes (up to 60%) including cuminaldehyde. The primary
phytochemicals that provide characteristic aroma of unheated whole seeds are 3p-
menthen-7al and cuminaldehyde in combination with other related aldehydes. Cumin also
contains safrole, a natural mutagenic compound, which is degraded by cooking.42 The
powerful antioxidant properties of Cumin seeds have been attributed to cocktail of occluded
phytochemicals. Antioxidant phytochemicals in cumin promote several important health
benefits. Studies in mice have revealed the inhibition of the induction of gastric squamous
cell carcinomas.43 In vivo studies in rats fed with cumin, have demonstrated a protective
effect against induced colonic cancer.44 Cumin seeds have been shown to be non toxic and
non carcinogenic when tested by the reverse mutation Salmonella typhimurium (TA100)
test.45
The powerful antioxidant characteristics of various phytochemicals within cumin prompted
us to test their efficacy in reducing sodium tetrachloroaurate to corresponding gold
nanoparticles. We hypothesized that the effective utilization of various phytochemicals that
contain functional groups such as carboxyl, amino, thiol and hydroxyl units present within
the multitudes of phytochemicals frameworks, including cumin aldehyde, α-and β-Pinene,
cuminyl alcohol, p-Cymine, and β-Terpinene within cumin (Figure 1) will provide
synergistic chemical reduction power for the reduction of gold salts into their corresponding
nanoparticles. We further hypothesized that the cumin aldehyde along with a host of
alcohols and terpinenes, cymines and pinenes of cumin will provide a coating of
phytochemicals on the gold nanoparticles thus, paving an unprecedented process for the
production and stabilization of gold nanoparticles in a singular green process. The rationale
behind this hypothesis is based on the reduction capabilities of cocktail of phytochemicals
present in cumin and their ability to chemically reduce gold (III) salts to nanoparticles with
consequent coating of phytochemicals, and a host of other phytochemicals present in cumin
on the freshly generated gold nanoparticles. We argued that validation of this hypothesis
would result in a versatile ‘Green Nanotechnology’ with consequent applications of gold
nanoparticles in a myriad of applications in nanomedicine and technology. On the
technology front, large scale production of nanoparticles through plant species and non toxic
seeds will minimize/eliminate chemical interventions thus, resulting in true green and non-
polluting industrial processes for the production of nanoparticle-based smart materials.46–
48 We herein, report an unprecedented synthetic route that involves the production of well-
defined spherical gold nanoparticles by simple mixing of cumin to an aqueous solution of
sodium tetrachloro aurate. Production of gold nanoparticles in this cumin–mediated
Green
Nanotechnological
process is achieved within 30 minutes. The gold nanoparticles generated
through cumin-mediated process were further stabilized by another naturally available plant
source glyco protein, Gum Arabic. Gum Arabic stabilized and cumin-initiated gold
nanoparticles exhibited long term stability (over a period of 4 weeks) suggesting that the
cocktail of phytochemicals in cumin, juxtaposed by glyco proteins of Gum Arabic, serve as
excellent coatings on nanoparticles and thus, provide robust shielding from aggregations. In
addition, the phytochemical coatings on nanoparticles have rendered non-toxic features to
these ‘Green Gold Nanoparticles’ as demonstrated through detailed MTT assays performed
on normal fibroblast cells. Results of our studies presenting a new ‘Nano-Naturo’
connection for the production and utility of gold nanoparticles for potential applications in
Nanomedicine and technology are discussed in the following sections.
EXPERIMENTAL
Materials and Methods
Chemicals and cumin precursors for the synthesis of gold nanoparticles (AuNPs) were
procured from standard vendors: NaAuCl4 (Alfa-Aesar) and Cumin from organic grocery
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sources. Transmission Electron Microscope (TEM) images were obtained on JEOL 1400
Transmission Electron Microscope (TEM), JEOL LTD., Tokyo, Japan. TEM samples were
prepared by placing 5 μL of gold nanoparticle solution on the 300 mesh carbon coated
copper grid and allowed to sit for five minutes; excess solution was removed carefully and
the grid was allowed to dry for an additional ten minutes. The average size and size
distribution of gold nanoparticles synthesized were determined by processing the TEM
image using image processing software such as Adobe Photoshop (with Fovea plug-ins).
The absorption measurements were recorded using Varian Cary 50 UV-Vis
Spectrophotometers with 1 mL of gold nanoparticle solution in disposable cuvettes of 10
mm path length.
Cumin Initiated and Gum Arabic Stabilized Gold Nanoparticles (Cu-AuNP)—To
a 20 mL vial was added 12 mg of gum arabic, 6 mL of doubly ionized water (DI). The
reaction mixture was stirred continuously at 45 °C for 10 minutes. To the stirring mixture
was added 100 μL of 0.1M NaAuCl4 (in DI water) followed by 300 mg of cumin seeds. The
color of the mixture turned purple-red from pale yellow within 5 minutes indicating the
formation of gold nanoparticles. The reaction mixture was stirred for an additional 15
minutes at RT. The gold nanoparticles thus formed were separated from residual cumin
seeds immediately using a 5 micron filter and were characterized by UV-Vis absorption
spectroscopy and TEM.
In vitro Stability Studies of Cu-AuNPs—
In vitro
stabilities of cumin-mediated gold
nanoparticles (Cu-AuNPs) were tested in the presence of NaCl, cysteine, histidine, HSA and
BSA solutions. Typically, 1 mL of gold nanoparticle solution was added to glass vials
containing 0.5 mL of each 5 % NaCl, 0.5 % cysteine, 0.2 M histidine, 0.5 % HSA, 0.5 %
BSA solutions respectively and incubated for 30 min. The stability and the identity of gold
nanoparticles were measured by recording UV absorbance after 30 min (Fig 3). The
plasmon resonance band at ~535 nm confirmed the retention of nanoparticulates in all the
above mixtures. TEM measurements also inferred the retention of the nanoparticulate
compositions of gold nanoconstructs in each medium signifying robust nature of these
nanoparticles under
in vitro
conditions.
Cell Culture—Minimum essential medium (MEM with nonessential amino acids,
powdered), HEPES, bovine insulin, streptomycin sulfate, penicillin-G, were obtained from
Sigma Chemical Company (St. Louis, MO); all were “cell culture tested” when available.
Bovine calf serum, phenol red (sodium salt), and lyophilized trypsin were obtained from
Gibco BRL (Grand Island, NY). PC-3 cells obtained from ATCC were maintained in RPMI
medium supplemented with 4.5 g/L D-glucose, 25 mM HEPES, 0.11 g/L sodium pyruvate,
1.5 g/L sodium bicarbonate, 2 mM L-glutamine and 10 % FBS and antibiotics. For MTT,
human fibroblasts primary cultures were used and obtained from Prof. Cris Lorson, Bond
Life Science Centre at University of Missouri-Columbia. The fibroblast cells were
maintained in DMEM with 10 pgmL−1 phenol red, 10 mM HEPES, 100 units mL−1
penicillin, 100 pgmL−1 streptomycin, and 10% donor bovine serum (maintenance medium).
In Vitro Cytotoxicity measurements (MTT Assay)—The
in vitro
cytotoxicity
evaluation of Cu-AuNPs was performed as described by the supplier (ATCC, USA). Briefly,
1 × 104 fibroblasts cells at the exponential growth phase were seeded in each well of a flat-
bottomed 96-well polystyrene-coated plate and were incubated at 37 °C for 24 h in CO2
incubator at 5% CO2 environment. Series of dilutions like 10, 50, 100, 150 and 200 μM
(gold atoms) of these nanoparticles were made in the medium. Each concentration was
added to the plate in pentaplet manner. After 24 h incubation, 10 μL per well MTT (stock
solution 5mg mL−1 PBS) (ATCC, USA) was added for 6 h and formazan crystals so formed
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were dissolved in 100 μL detergent. The plates were kept for 18 h in dark at 25 °C to
dissolve all the crystals and the intensity of developed color was measured by micro plate
reader (Dynastic MR 5000, USA) operating at 570 nm wavelength. Wells with complete
medium, nanoparticles, and MTT, but without cells were used as blanks. Untreated cells
were considered 100 % viable.
Cellular Uptake of Cu-AuNPs—PC-3 prostate cancer cells obtained from ATCC were
used for the
in-vitro
cell internalization analysis. PC-3 cells were maintained in RPMI
medium supplemented with 4.5 g/L D-glucose, 25 mM HEPES, 0.11 g/L sodium pyruvate,
1.5 g/L sodium bicarbonate, 2 mM L-glutamine and 10 % FBS and antibiotics. Known
concentration of Cu-AuNPs (100 μg/mL) were added to each type of cells (~10000 cells)
and incubated for 4 h at 37°C. Following incubation, cells were washed three times with
PBS, centrifuged into small pellets, and fixed with 2% glutaraldehyde, 2%
paraformaldehyde in sodium cacodylate buffer (0.1 M). The cells were further fixed with
1% buffered osmium tetraoxide and dehydrated in an ethanol series before embedding in
Epon-Spurr epoxy resin. Sections (75–85 nm) were cut using Leica Ultracut UCT
ultramicrotome and placed on a TEM grid. The sections were post-stained with uranyl
acetate and lead citrate for organelle visualization. The prepared samples were viewed with
JEOL 1400 Transmission Electron Microscope.
Results and discussion
Our overall long term objectives toward the design and development of biocompatible gold
nanomaterials for medical applications has prompted us to pursue the application of
phytochemicals in plants/seeds and various vectors from the plant kingdom for the synthesis
of gold nanoparticles. Our new effort for the production of gold nanoparticles uses direct
interaction of sodium tetrachloaurate with cumin seeds and gum arabic (Scheme 1) without
intervention of any toxic chemical reducing agents or additional chemicals. This rationale of
using 100% green resources for conducting chemical reactions thus qualifies the condition
of a true 100% green chemical process. The important constituents of various
phytochemicals in cumin are outlined in Figure 1.
The UV absorption measurements showed that the plasmon resonance wavelength, λmax of
Cu-AuNPs is ~535 nm (Figure 2). The sizes of Cu-AuNPs are in the range of 10–15 nm as
measured from TEM techniques. The current discovery on the unique chemical power of
phytochemicals in cumin in initiating nanoparticle formation is of paramount importance in
the context of the production of gold nanoparticles for medical and technological
applications under non toxic conditions. One of the paramount prerequisites of utilizing
AuNPs for
in vivo
imaging and therapy applications is that the nanoparticles should be
produced and stabilized in biologically benign media. 27,49,50 With the available methods
of producing AuNPs, it is often necessary to remove unreacted toxic chemicals and
byproducts. Typical known methods of making gold nanoparticles utilize harsh conditions,
such as the application of sodium borohydride to reduce AuCl4−.15,16,51, 52 Although such
processes lead to efficient production of gold nanoparticles, the presence of sodium
borohydride, even in trace amounts, may be unsuitable for use in biomedical applications of
gold nanoparticles. The high reduction capabilities of sodium borohydride result in
reduction of biogenic chemical functionalities present on peptide backbones, thus either
reducing or eliminating the biospecificity of biomolecules. Normally, thiol containing
organic compounds are employed to stabilize AuNPs from agglomeration.51 Thiol-gold
nanoparticle interaction is strong and makes gold nanoparticles highly stable.53, 54
Therefore, such AuNPs once stabilized by thiols cannot be further conjugated to useful drug
moieties including peptides, proteins and various biochemical vectors that are normally used
to target diagnostic and therapeutic gold nanoparticles on to tumor and various disease sites
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in the body. This means that the thiol-stabilized AuNPs will have limited applicability in the
development of AuNP-labeled biomolecules for use in the design of target specific
nanoscale imaging or therapeutic agents. Other methods that have been described in the
literature utilize cocktail of chemicals in their production protocols. Such techniques are not
environmentally friendly and have many drawbacks that impede the efficient utilization of
AuNPs in biomedicine applications.
Nanoparticle Characterization and Size Distribution—Physicochemical properties,
such as size, charge, and morphology of gold nanoparticles generated using cumin seeds in
aqueous solutions, were determined by three independent techniques; Transmission Electron
microscopy (TEM), Differential Centrifugal Sedimentation (DCS, Disc Centrifuge, CPS
Instruments), and Dynamic light scattering (DLS). TEM and CPS were used to determine
the core size of gold nanoparticles and DLS was used to evaluate the size of cumin initiated
and gum arabic coated gold.
Size and Morphology—TEM measurements on Cu-AuNPs show that the particles are
spherical in shape within the size range of 10–15 nm (Table 1). Size distribution analysis of
Cu-AuNPs confirms that particles are well dispersed (Figure 2 and Table 1). DCS technique
measures sizes of nanoparticles by determining the time required for nanoparticles to
traverse a sucrose density gradient created in a disc centrifuge.55 Both the techniques, TEM
and DCS, provide sizes of metallic-gold cores. Gold nanoparticulate sizes measured by
TEM and DCS are 13±4 and 12±2 nm respectively. (Figure 2 and Table 1). Dynamic light
scattering method was employed to calculate the sizes of gold nanoparticles coated with
phytochemicals of cumin and gum arabic (hydrodynamic radius). The phytochemical
coatings on nano-gold surfaces are expected to cause substantial changes in the
hydrodynamic radius of Cu-AuNPs. Hydrodynamic diameter of Cu-AuNP as determined
from DLS measurements is 77±1 nm, suggesting that cumin phytochemicals (essential oils,
free amino acids, variety of flavonoid glycosides) are capped on gold nanoparticles. The
measurement of charge on nanoparticles and Zeta Potential (ζ) provides crucial information
on the stability of nanoparticle dispersion. The magnitude of measured zeta potential is an
indication of repulsive forces that are present and can be used to predict the long-term
stability of the nanoparticulate dispersion. The stability of nanoparticulate dispersion
depends upon the balance of the repulsive and attractive forces that exist between
nanoparticles as they approach one another. If all the particles have a mutual repulsion then
the dispersion will remain stable. However, little or no repulsion between particles, lead to
aggregation. The negative zeta potential of −15±1 mV for Cu-AuNP indicates that the
particles repel each other and there is no tendency for the particles to aggregate (Table 1 and
Figure 2).
Role of Cumin Phytochemicals—Synthetic conditions have been optimized for the
quantitative large scale conversions of NaAuCl4 to the corresponding AuNPs using cumine
seeds and gum arabic as a stabilizer. The chemical roles of different phytochemicals in
cumin responsible for the production of Cu-AuNPs are still not fully understood but we
believe that water soluble constituents of cumin may be playing a major role in the overall
reduction process of NaAuCl4.
The main phytochemicals present in cumin seeds consist of volatile essential oils (5 %),
numerous free amino acids and a variety of flavonoid glycosides, including derivatives of
apigenin and luteolin.35–41 In order to understand the critical roles of the various
phytochemicals present in cumin seeds on the overall reduction of NaAuCl4 to the
corresponding gold nanoparticles, we have performed a series of independent experiments
using commercially available chemicals which are present in cumin seeds. Results of our
experiments using those chemical compounds have unambiguously confirmed that none of
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the individual constituents are potentially reducing and stabilizing the gold nanoparticles,
instead the cocktails of all the chemicals along with gum arabic are responsible for the
synthesis of gold nanoparticles in aqueous medium. However, each individual
phytochemicals failed to provide effective coating to shield the nanoparticles from
agglomeration. In order to capitalize on the reduction powers of the components present in
cumin, we have utilized gum Arabic (a glycoprotein) as a naturally available stabilizing
agent in our reactions. Results from these experiments have revealed that the synergistic
effect of all the constituents (essential oil and flavonoid derivatives) present in cumin seeds
act as an excellent reducing agents to reduce the Au(III) to the corresponding gold
nanoparticles which are stabilized by gum arabic. These experiments have unambiguously
confirmed that cumin constituents can serve the important role in reducing gold salts to gold
nanoparticles and the gum arabic provides the required stabilization to the system.
It is remarkable to note that the use of gum arabic, in the above reactions provides additional
advantages. The use of gum arabic with cumin has increased the stability of the
nanoparticles.56 This observation demonstrates that gum arabic may be presumably serving
as a biochemical platform to drive such reactions to completion with consequent production
of well defined and uniform spherical gold nanoparticles by cumin constituents.
In Vitro Stability Studies—The most important criteria for
in vivo
molecular imaging
applications is the stability of gold nanoparticles over a reasonable time period. The stability
of Cu-AuNPs was evaluated by monitoring the plasmon (λmax) in 0.5 % Cysteine, 0.2 M
Histidine, 0.5 % Human Serum Albumin (HSA), 0.5 % Bovine Serum Albumin (BSA) or 5
% NaCl solutions over 30 min. (Figure 3) The stability of Cu-AuNPs has also been checked
at
p
H 5, 7 and
p
H 9 phosphate buffer solutions. The plasmon wavelength in all the above
formulations showed minimal shifts of ~1–5 nm. Our results from these
in vitro
stability
studies have confirmed that the gold nanoparticles are intact and thus, demonstrate excellent
in vitro
stability of Cu-AuNPs in biological fluids at physiological
p
H (Figure 3). For
various biomedical applications which require lower concentrations of gold, it is vitally
important that dilutions of nanoparticle solutions do not alter their characteristic chemical
and photophysical properties. We have undertaken a detailed investigation to ascertain the
effect of dilution on the stability of Cu-AuNP. In order to establish the stability of Cu-
AuNPs under dilution, the plasmon resonance wavelength (λmax) was monitored after every
successive addition of 0.1 mL of doubly ionized (DI) water to 1 mL of Cu-AuNP solutions.
The absorption intensity at λmax is found to be linearly dependent on the concentration of
Cu-AuNPs, in accordance with Beer Lambert’s law as shown in Figure 4. It is important to
recognize that λmax of gold nanoparticles did not change at very dilute conditions. These are
typical concentrations encountered when working at cellular levels.
It is thus conceivable that the cocktail of phytochemicals in cumin along with non-toxic
phytochemical gum arabic (Figure 1) are acting synergistically in stabilizing gold
nanoparticles from any agglomerations in solution. It is also remarkable that this
biocompatible Cu-AuNPs remains stable in aqueous media for over a month. These results
suggest that the green nanotechnological process reported herein provides both the
production and stabilization processes under mild conditions without the intervention of any
man made harsh chemicals.
Cytotoxicity Studies—The cytotoxicity of Cu-AuNP under
in vitro
conditions in human
fibroblast cells was examined in terms of the effect of gold nanoparticles on cell
proliferation by the MTT assay. Untreated cells as well as cells treated with 10, 50, 100, 150
and 200 μM concentrations of gold nanoparticles for 24 h were subjected to the MTT assay
for cell viability determination. In this assay, only cells that are viable after 24 h exposure to
the sample are capable to metabolize a dye (3-(4,5-dimethylthiazol-2-yl)-2,5-
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diphenyltetrazolium bromide) efficiently and produce a purple coloured crystals which is
dissolved in a detergent and analyzed spectrophotometrically. After 24 h of post treatment,
fibroblast cells showed excellent viability even up to 150μM concentrations of Cu-AuNP
(Figure 5). These results clearly demonstrate that the phytochemicals within cumin and gum
arabic provide a non toxic coating on gold nanoparticles. It is also important to recognize
that a vast majority of Gold (I) and Gold (III) compounds exhibit varying degrees of
cytotoxicity to a variety of cells.57 The lack of any noticeable toxicity of Cu-AuNP provides
new opportunities for the safe delivery and applications of such nanoparticles in molecular
imaging and therapy.
Cellular Interactions—Cellular internalization studies of gold nanoparticles solutions
provide insights into cellular uptake and such information will enhance the scope of gold
nanoparticles in biomedicine. Gold nanoparticles are currently investigated for their
potential applications as diagnostic/therapeutic agents, therapeutic delivery vectors, and
intracellular imaging agents.58–63 Selective cell and nuclear targeting of gold nanoparticles
will provide new pathways for the site specific delivery of gold nanoparticles as diagnostic/
therapeutic agents. A number of studies have demonstrated that phytochemicals in soybeans
and tea have an ability to penetrate the cell membrane and internalize within the cellular
matrix.33, 34, 64, 65 Cancer cells are highly metabolic and porous in nature and are known
to internalize solutes rapidly compared to normal cells.66, 67 Therefore, we hypothesized
that cumin-derived gold nanoparticles will also show internalization within cancer cells. We
undertook the cellular interactions and uptake studies via incubation of aliquots of Cu-AuNP
with prostate (PC-3) cancer cells. TEM images of prostate tumor cells post treated with Cu-
AuNP unequivocally validated our hypothesis. Significant internalization of nanoparticles
via endocytosis within the PC-3 cells was observed (Figure 6). The internalization of
nanoparticles within cells could occur via processes including phagocytosis, fluid-phase
endocytosis, and receptor-mediated endocytosis. The viability of PC-3 cells internalized
with Cu-AuNP suggests that the phytochemical coating renders the nanoparticles to be non-
toxic to cells and corroborate the results as seen in the cytotoxicity studies discussed above.
This internalization of gold nanoparticles, keeping the cellular machinery intact, will provide
new opportunities for probing cellular processes via nanoparticulate-mediated imaging.
Conclusions—The unique chemical, biological, photophysical and magnetic properties of
gold nanoparticles will continue to unravel a rich applied and commercially viable products
within the medical, civilian, defence, environmental and space exploration sectors. Over the
next decade, advances in nanotechnology as they relate to nanomedicine and technological
applications will lightly impact all of us. Although there is no question on the scientific
power and the positive impact of nanoscience and nanotechnology in transforming medical
diagnosis and therapy, the potential toxic side effects of nanoparticles administered via
intravenous or oral pathways or when nanoparticles are used in a myriad of finished
products cannot be discounted. Therefore, concerted efforts must be invested in the
development of non-toxic nanoparticles for utility in a wide spectrum of applications. The
studies reported in this paper provide the power of plant sciences to bring about a paradigms
shift on future developments in nanotechnology. Our results have demonstrated the unique
kinetic propensity of Phytochemicals, present in cumin, to reduce the gold metal at the
micro or in picomolar/subnanomolar concentrations, to the corresponding gold
nanoparticles. The versatile phytochemical mediated green nanotechnological process has
been shown to be effective in both the generation and stabilization of non-toxic gold
nanoparticles for direct applications in a myriad of diagnostic and therapeutic applications.
Occlusion of cancer fighting phytochemicals in various plant species and their future utility
in the development of tumor specific gold nanoparticles will provide unprecedented
opportunities toward the design and development of functional gold nanoparticles that can
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be safely produced, stored and shipped world wide. The connection between plant sciences
and nanotechnology has the potential to develop an attractive symbiosis between green
revolution and nanotechnology with realistic prospects for minimizing/eliminating the
application and generation of toxic chemicals that destroy living organisms and our
environment.
Acknowledgments
This work has been supported by the generous support from the National Institutes of Health/National Cancer
Institute under the Cancer Nanotechnology Platform program (grant number: 5R01CA119412-01), NIH -
1R21CA128460-01 and University of Missouri-Research Board - Program C8761 RB 06-030.
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Figure 1.
Composition of constituents of various phytochemicals in cumin.
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Figure 2.
UV-visible spectrum of Cu-AuNps synthesized by cumin seeds upon reduction of NaAuCl4
in gum Arabic. The inset shows the TEM and size distribution histogram of the gold
nanoparticle solution.
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Figure 3.
UV-visible spectra of Cu-AuNPs showing in vitro stability of the nanoparticles in different
media, e.g. 5 % NaCl, 0.5 % cysteine, 0.2M Histidine, 0.5 % HSA, 0.5 % BSA and at
different pH.
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Figure 4.
Change in plasmon absorption maximum (λmax) of Cu-AuNP as a function of dilution.
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Figure 5.
Cell viability of fibroblast cells after 24 h post incubation with increasing amounts of
CuAuNPs.
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Figure 6.
TEM images showing endocytosis of Cu-AuNP in Prostate Cancer (PC-3) cells.
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Scheme 1.
Synthesis of Cu-AuNPs from cumin seeds and gum Arabic.
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Table 1
Physicochemical data parameters of Cu-AuNPs.
Size
[nm] Zeta Potential
[mV] In Vitro Stability
Sample TEM DCS DLS NaCl
(5 %) Cysteine
(0.5 %) Histidine
(0.2 M) HSA
(0.5%) BSA
(0.5%) pH 9
(PBS)
Cu-AuNP 13±4 12±2 77±1
a
−15.0 S S S S S S
a
Hydrodynamic Diameter.
b
S: Stable.
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