Growth Kinetics of Gold Nanoparticle Formation from Glycated Hemoglobin (original) (raw)
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Optimizing a Novel Method for Synthesizing Gold Nanoparticles: Biophysical Studies
Journal of Cancer Science & Therapy, 2012
The properties of Gold Nanoparticles (GNPs) make them useful for cancer therapy, diagnostics and imaging. For the application of GNPs in therapy and drug delivery there is a great necessity to synthesize known particle size of GNPs with simple methods. This study aimed to optimize a novel simple method for synthesizing GNPs.
Growth kinetics and controlled auto-assembly of gold nanoparticles
Nanoparticles superlattices can be prepared by self-assembly of hybrid nanoparticles composed of a metallic core surrounded by an organic passivating layer. These superlattices are promising materials for applications in various fields such as recording media, light-emitting devices, biological tags, catalysts, solar cells, and sensors. The self-assembly is only possible when the nanoparticles display a narrow size distribution. The citrate reduction of gold(III) in water is one of the most commonly used synthetic pathways for the preparation of gold colloids [1]. The nucleation and growth mechanisms remain however unclear and are the subject of intense research. We have investigated the synthesis of gold nanoparticles under different experimental conditions and using different experimental techniques in order to gain insight into their formation mechanism.
Time dependent formation of gold nanoparticles in yeast cells: A comparative study
Biochemical Engineering Journal, 2011
Two different strains of yeast, Saccharomyces cerevisiae, AP22 and CCFY-100 were studied for bioaccumulation of gold in the form of H198AuCl4. Thin sectioning and subsequent study by transmission electron microscopy (TEM) reveals that Au3+ was in situ reduced to Au(0) and nano sized gold particles were formed inside the cell. Very low dose γ-energy being responsible for reduction of cationic gold in the polymeric cytoplasm matrix. The formation and entry of gold nanoparticles in the yeast cells were studied as a function of time at certain intervals starting from 15 min to 72 h. The gold nanoparticles gradually moved inward as a function of time from cell wall to cytoplasm to nucleus and finally accumulated in the nucleolus of the cell. TEM image of budding yeast shows that gold nanoparticles are not transferred to the new generation yeast cells.► This paper for the first time addresses the migration kinetics of nanoparticles inside a cell. ► Gold nanoparticles gradually move inward as a function of time from cell wall to cytoplasm to nucleus. ► The gamma energy of 198Au is solely responsible factor in the reduction of Au and formation of gold nanoparticles. ► TEM image of budding yeast shows that gold nanoparticles are not transferred to the new generation yeast cells.
Journal of photochemistry and photobiology. B, Biology, 2017
The nature of interactions between heme protein human hemoglobin (HHb) and gold nanoparticles of two different morphologies that is GNP (spherical) and GNS (star-shaped) have been investigated by using UV-vis absorption, steady state fluorescence, synchronous fluorescence, resonance light scattering (RLS), time resolved fluorescence, FT-IR, and circular dichroism (CD) techniques under physiological condition of pH ~7 at ambient and different temperatures. Analysis of the steady state fluorescence quenching of HHb in aqueous solution in the presence of GNP and GNS suggests that the nature of the quenching is of static type. The static nature of the quenching is also confirmed from time resolved data. The static type of quenching also indicates the possibility of formation of ground state complex for both HHb-GNP and HHb-GNS systems. From the measurements of Stern-Volmer (SV) constants KSV and binding constants, KA and number of binding sites it appears that HHb forms stronger binding...
Scientific Reports, 2016
Biosynthesis of nanoparticles has gained great attention in making the process cost-effective and ecofriendly, but there are limited reports which describe the interdependency of physical parameters for tailoring the dimension and geometry of nanoparticles during biological synthesis. In the present study, gold nanoparticles (GNPs) of various shapes and sizes were obtained by modulating different physical parameters using Trichoderma viride filtrate. The particles were characterized on the basis of visual observation, dynamic light scattering, UV-visible spectroscopy, transmission electron microscopy, fourier transform infrared spectroscopy, and X ray diffraction. While the size varied from 2-500 nm, the shapes obtained were nanospheres, nanotriangles, nanopentagons, nanohexagons, and nanosheets. Changing the parameters such as pH, temperature, time, substrate, and culture filtrate concentration influenced the size and geometry of nanoparticles. Catalytic activity of the biosynthesized GNP was evaluated by UV-visible spectroscopy and confirmed by gas chromatography-mass spectrometric analysis for the conversion of 4-nitrophenol into 4-aminophenol which was strongly influenced by their structure and dimension. Common practices for biodegradation are traditional, expensive, require large amount of raw material, and time taking. Controlling shapes and sizes of nanoparticles could revolutionize the process of biodegradation that can remove all the hurdles in current scenario. In the rapidly growing area of nanomaterial research, gold nanoparticles have entered into a new arena, opening new possibilities in catalysis 1 , diagnostics and biomedicine 2 , optics 3,12 , imaging 4 , electronics 13 , sensing 5,6 , and agriculture 7. The functions of gold nanoparticles heavily rely upon their structure, size and morphology, so finding a way to modulate nanoparticles biosynthesis is an important aspect of the research 8-10. Shape and symmetry-dependent mechanical properties of metallic gold on the nanoscale has already been elucidated by Mahmoud et al. 11. Despite tremendous progress in the synthesis of gold nanocrystals of various shapes and sizes with good yield and monodispersity via chemical routes 14,15 , the conventional approaches remain unimplementable due to requirement of harsh chemicals, high temperature, pressure and are also non eco-friendly 16,17. Biogenic synthesis of nanoparticles has emerged as an absolute alternative and green approach, making the process cheaper and safer 15. Several reports are available for biosynthesis of gold nanoparticles by plants, fungi, bacteria, and actinomycetes. Fungi like Verticillium sp., Phoma sp., Fusarium oxysporum, Aspergillus fumigatus, and Rhizopus oryzae are considered to be the best source for synthesis of nanoparticles 15. They are the producers of significant amounts of proteins and secondary metabolites secreted extracellularly, which act as both reducing and stabilizing agent for nanoparticles biosynthesis 16. Their requirements for growth are simple, easy to manipulate and downstream processing is much easier as compared with other microorganisms. In a previous study carried out in our group, Trichoderma viride and Hypocrea lixii have been reported for synthesis of gold nanoparticles within 10 min 16 .
Gold Nanoparticles Obtained by Bio-precipitation from Gold(III) Solutions
Journal of Nanoparticle Research, 1999
The use of metal nanoparticles has shown to be very important in recent industrial applications. Currently gold nanoparticles are being produced by physical methods such as evaporation. Biological processes may be an alternative to physical methods for the production of gold nanoparticles. Alfalfa biomass has shown to be effective at passively binding and reducing gold from solutions containing gold(III) ions and resulting in the formation of gold(0) nanoparticles. High resolution microscopy has shown that five different types of gold particles are present after reaction with gold(III) ions with alfalfa biomass. These particles include: fcc tetrahedral, hexagonal platelet, icosahedral multiple twinned, decahedral multiple twinned, and irregular shaped particles. Further analysis on the frequency of distribution has shown that icosahedral and irregular particles are more frequently formed. In addition, the larger particles observed may be formed through the coalescence of smaller particles. Through modification of the chemical parameters, more uniform particle size distribution may be obtained by the alfalfa bio-reduction of gold(III) from solution.
Synthesis of Gold Nanospheres and Nanotriangles by the Turkevich Approach
Journal of Nanoscience and Nanotechnology, 2005
Gold nanoparticles of triangular morphology possess interesting optical properties with potential application in medicine and infrared absorbing coatings, however, little is known about conditions that favor their growth. In this paper, we have reinvestigated a time-tested recipe for the formation of gold nanospheres by citrate reduction of aqueous gold ions under boiling conditions (Turkevich recipe). Our principle findings are that gold nanotriangle formation is kinetically controlled and is highly favored at low temperatures. Furthermore, the presence of chloride ions from the precursor chloroaurate ions plays a major role in promoting the growth of 111 oriented triangular/truncated triangular particles. The presence of bromide and iodide ions that possess the ability to replace surface-bound chloride ions inhibits triangle formation to varying degrees.
Turkevich in New Robes: Key Questions Answered for the Most Common Gold Nanoparticle Synthesis
ACS Nano, 2015
This contribution provides a comprehensive mechanistic picture of the gold nanoparticle synthesis by citrate reduction of HAuCl 4 , known as Turkevich method, by addressing five key questions. The synthesis leads to monodisperse final particles as a result of a seed-mediated growth mechanism. In the initial phase of the synthesis, seed particles are formed onto which the residual gold is distributed during the course of reaction. It is shown that this mechanism is a fortunate coincidence created by a favorable interplay of several chemical and physicochemical processes which initiate but also terminate the formation of seed particles and prevent the formation of further particles at later stages of reaction. Since no further particles are formed after seed particle formation, the number of seeds defines the final total particle number and therefore the final size. The gained understanding allows illustrating the influence of reaction conditions on the growth process and thus the final size distribution.
Evolution of size and shape of gold nanoparticles during long-time aging
h i g h l i g h t s < The initial Au particle size of 2e5 nm increased to 25 nm in one year of storage. < The main mechanisms of Au particle growth are Ostwald ripening and fusion. < The initial spherical morphology changed to regular shapes. < Twin boundaries have an important effect on the evolution of morphology.
Gold nanoparticles a renaissance in gold chemistry
Gold Bulletin, 1996
Vapour synthesis techniques have been used to prepare nanoparticulate dispersions of gold and other precious metals in non-aqueous solvents. The dimensions of these solvent-stabilised particles, which can be controlled within the 1-3nm size regime, effectively encompass the areas of molecular chemistry (as typified by high-nuclearity metal clusters) and the smaller colloidal metals. Gold nanoparticles differ from those of the other metals in exhibiting unusual time-and concentration-dependent behaviour. A regime of preparative conditions under which 1-3nm size gold particles, which are stable with respect to aggregation as a function of time, is defined. Some implications for these new developments are indicated.