Bacterial Enzyme Mediated Biosynthesis of Gold Nanoparticles

2007 ◽  
Vol 7 (12) ◽  
pp. 4369-4377 ◽  
Author(s):  
Atul Bharde ◽  
Aarohi Kulkarni ◽  
Mala Rao ◽  
Asmita Prabhune ◽  
Murali Sastry
Keyword(s):  
Gold Nanoparticles ◽  
Shape Control ◽  
Incubation Temperature ◽  
Synthesis Methods ◽  
Chemical Methods ◽  
Experimental Conditions ◽  
Protease Enzyme ◽  
Bacterial Enzyme ◽  
Drastic Effect ◽  
Anisotropic Metal

Development of synthesis methods for anisotropic metal nanoparticles is of considerable interest due to their remarkable optoelectronic properties. Various shapes ranging from rods to cubes to tetrapods and prisms may be obtained by chemical methods. Here we show that anisotropic gold nanoparticles can be synthesized biologically by the bacterium Actinobacter spp. when challenged with gold chloride in the presence of Bovine serum albumin (BSA). We also observed that synthesis of gold nanoparticles occur with simultaneous induction of the protease enzyme secreted by the bacterium in the presence of BSA. The presence of BSA helps to enhance the rate of gold nanoparticles biosynthesis and may also impart some shape control. Controlling simple experimental conditions like incubation temperature and presence or absence of oxygen have drastic effect on the reaction rate and the morphology of the particles. Various assay experiments show that the presence of enzyme protease can act as a reducing as well as shape directing agent.

Molecularly Imprinted Sensor for Ascorbic Acid Based on Gold Nanoparticles and Multiwalled Carbon Nanotubes

2020 ◽  
Vol 16 (7) ◽  
pp. 905-913
Author(s):  
Youyuan Peng ◽  
Qingshan Miao
Keyword(s):  
Carbon Nanotubes ◽  
Gold Nanoparticles ◽  
Ascorbic Acid ◽  
Multiwalled Carbon Nanotubes ◽  
Ph Value ◽  
Biological Fluids ◽  
Water Soluble ◽  
Multiwalled Carbon ◽  
Experimental Conditions ◽  
Molecularly Imprinted

Background: L-Ascorbic acid (AA) is a kind of water soluble vitamin, which is mainly present in fruits, vegetables and biological fluids. As a low cost antioxidant and effective scavenger of free radicals, AA may help to prevent diseases such as cancer and Parkinson’s disease. Owing to its role in the biological metabolism, AA has also been utilized for the therapy of mental illness, common cold and for improving the immunity. Therefore, it is very necessary and urgent to develop a simple, rapid and selective strategy for the detection of AA in various samples. Methods: The molecularly imprinted poly(o-phenylenediamine) (PoPD) film was prepared for the analysis of L-ascorbic acid (AA) on gold nanoparticles (AuNPs) - multiwalled carbon nanotubes (MWCNTs) modified glass carbon electrode (GCE) by electropolymerization of o-phenylenediamine (oPD) and AA. Experimental parameters including pH value of running buffer and scan rates were optimized. Scanning electron microscope (SEM), fourier-transform infrared (FTIR) spectra, cyclic voltammetry (CV) and differential pulse voltammetry (DPV) were utilized for the characterization of the imprinted polymer film. Results: Under the selected experimental conditions, the DPV peak currents of AA exhibit two distinct linear responses ranging from 0.01 to 2 μmol L-1 and 2 to 100 μmol L-1 towards the concentrations of AA, and the detection limit was 2 nmol L-1 (S/N=3). Conclusion: The proposed electrochemical sensor possesses excellent selectivity for AA, along with good reproducibility and stability. The results obtained from the analysis of AA in real samples demonstrated the applicability of the proposed sensor to practical analysis.

scholarly journals Surfactant-Free Shape Control of Gold Nanoparticles Enabled by Unified Theoretical Framework of Nanocrystal Synthesis

2017 ◽  
Vol 29 (21) ◽  
pp. 1605622 ◽  
Author(s):  
Matthew A. Wall ◽  
Stefan Harmsen ◽  
Soumik Pal ◽  
Lihua Zhang ◽  
Gianluca Arianna ◽  
...  
Keyword(s):  
Gold Nanoparticles ◽  
Shape Control ◽  
Theoretical Framework ◽  
Nanocrystal Synthesis

The influence of experimental conditions on the assessment of the toxicity of 2,4-dichlorophenol to anaerobic degradative bacteria

2002 ◽  
Vol 45 (10) ◽  
pp. 61-63 ◽  
Author(s):  
N. Nitayapat ◽  
I.A. Watson-Craik
Keyword(s):  
Steady State ◽  
Incubation Temperature ◽  
Anaerobic Bacteria ◽  
Relative Activity ◽  
Experimental Conditions ◽  
Fermentative Bacteria ◽  
Two Temperatures

The toxicity of 2,4-dichlorophenol (2,4-DCP) to anaerobic bacteria in refuse cultures was investigated at two temperatures (30 and 37°C) and after two different exposure periods to the toxicants. It was shown that at 0.52mM 2,4-DCP the time of exposure of microorganisms to 2,4-DCP affected the relative activity (Av) of the production of methane. Av values at the beginning of the steady-state phase were lower than those recorded two weeks later. The incubation temperature selected also critically affected the assessment of anaerobic toxicity; at 37°C an imbalance of the activities of fermentative bacteria and acetogens with those of methanogens was observed.

scholarly journals Factors Influencing the Surface Functionalization of Citrate Stabilized Gold Nanoparticles with Cysteamine, 3-Mercaptopropionic Acid or l-Selenocystine for Sensor Applications

Chemosensors ◽  
2020 ◽  
Vol 8 (3) ◽  
pp. 80
Author(s):  
Georgia I. Sakellari ◽  
Nicole Hondow ◽  
Philip H.E. Gardiner
Keyword(s):  
Gold Nanoparticles ◽  
Co Adsorption ◽  
Limiting Factor ◽  
Experimental Conditions ◽  
Mercaptopropionic Acid ◽  
X Ray ◽  
Sensor Applications ◽  
Factors Influencing ◽  
Electrostatic Repulsions ◽  
Functionalized Aunps

Thiols and selenides bind to the surface of gold nanoparticles (AuNPs) and thus provide suitable platforms for the fabrication of sensors. However, the co-existence of adsorbed citrate on the surface of the nanoparticles can influence their functionalization behavior and potentially their sensing performance measured by the extent of particle aggregation. In this study, the functionalization of purchased (7.3 ± 1.2 nm) and in-house prepared AuNPs (13.8 ± 1.2 nm), under the same experimental conditions with either cysteamine (Cys), 3-mercaptopropionic acid (3-MPA), or l-selenocystine (SeCyst) was investigated. 1H-NMR measurements showed distinct citrate signatures on the in-house synthesized citrate-stabilized AuNPs, while no citrate signals were detected on the purchased AuNPs other than evidence of the presence of α-ketoglutaric acid. Carboxylate-containing species attributed to either citrate or α-ketoglutaric acid were identified in all functionalized AuNPs. ATR-FTIR spectroscopy confirmed the functionalization of AuNPs with Cys and 3-MPA, and energy dispersive X-ray (EDX) spectroscopy measurements suggested the formation of SeCyst functionalized AuNPs. Co-adsorption rather than displacement by the functionalizing agents and carboxylate-containing molecules was indicated, which for Cys and SeCyst functionalized AuNPs was also the aggregation limiting factor. In contrast, the behavior of 3-MPA functionalized AuNPs could be attributed to electrostatic repulsions between the functionalized groups.

scholarly journals Mesoporous Silica-gold Films for Straightforward, Highly Reproducible Monitoring of Mercury Traces in Water

Nanomaterials ◽  
2018 ◽  
Vol 9 (1) ◽  
pp. 35 ◽  
Author(s):  
Anna Mutschler ◽  
Vivian Stock ◽  
Lena Ebert ◽  
Emma Björk ◽  
Kerstin Leopold ◽  
...  
Keyword(s):  
Gold Nanoparticles ◽  
Mesoporous Silica ◽  
Water Sample ◽  
River Water ◽  
Silicon Wafer ◽  
Mercury Concentration ◽  
Atomic Fluorescence Spectrometry ◽  
Silica Layer ◽  
Experimental Conditions

Trace-level detection of mercury in waters is connected with several complications including complex multistep analysis routines, applying additional, harmful reagents increasing the risk of contamination, and the need for expensive analysis equipment. Here, we present a straightforward reagent-free approach for mercury trace determination using a novel thin film sampling stick for passive sampling based on gold nanoparticles. The nanoparticles supported on a silicon wafer and further covered with a thin layer of mesoporous silica. The mesoporous silica layer is acting as a protection layer preventing gold desorption upon exposure to water. The gold nanoparticles are created by thermal treatment of a homogenous gold layer on silicon wafer prepared by vacuum evaporation. This gold-covered substrate is subsequently covered by a layer of mesoporous silica through dip-coating. Dissolved mercury ions are extracted from a water sample, e.g., river water, by incorporation into the gold matrix in a diffusion-controlled manner. Thus, the amount of mercury accumulated during sampling depends on the mercury concentration of the water sample, the accumulation time, as well as the size of the substrate. Therefore, the experimental conditions can be chosen to fit any given mercury concentration level without loss of sensitivity. Determination of the mercury amount collected on the stick is performed after thermal desorption of mercury in the gas phase using atomic fluorescence spectrometry. Furthermore, the substrates can be re-used several tens of times without any loss of performance, and the batch-to-batch variations are minimal. Therefore, the nanogold-mesoporous silica sampling substrates allow for highly sensitive, simple, and reagent-free determination of mercury trace concentrations in waters, which should also be applicable for on-site analysis. Successful validation of the method was shown by measurement of mercury concentration in the certified reference material ORMS-5, a river water.

Synthesis of Silver Nanoparticles and their Biomedical Applications - A Comprehensive Review

2019 ◽  
Vol 25 (24) ◽  
pp. 2650-2660 ◽  
Author(s):  
Rajasree Shanmuganathan ◽  
Indira Karuppusamy ◽  
Muthupandian Saravanan ◽  
Harshiny Muthukumar ◽  
Kumar Ponnuchamy ◽  
...  
Keyword(s):  
Silver Nanoparticles ◽  
Biomedical Applications ◽  
Antibacterial Agents ◽  
Cost Effective ◽  
Metallic Silver ◽  
Synthesis Methods ◽  
Burn Wound ◽  
Chemical Methods ◽  
Biological Sources ◽  
Physical And Chemical

Generally, silver is considered as a noble metal used for treating burn wound infections, open wounds and cuts. However, the emerging nanotechnology has made a remarkable impact by converting metallic silver into silver nanoparticles (AgNPs) for better applications. The advancement in technology has improved the synthesis of NPs using biological method instead of physical and chemical methods. Nonetheless, synthesizing AgNPs using biological sources is ecofriendly and cost effective. Till date, AgNPs are widely used as antibacterial agents; therefore, a novel idea is needed for the successful use of AgNPs as therapeutic agents to uncertain diseases and infections. In biomedicine, AgNPs possess significant advantages due to their physical and chemical versatility. Indeed, the toxicity concerns regarding AgNPs have created the need for non-toxic and ecofriendly approaches to produce AgNPs. The applications of AgNPs in nanogels, nanosolutions, silver based dressings and coating over medical devices are under progress. Still, an improvised version of AgNPs for extended applications in an ecofriendly manner is the need of the hour. Therefore, the present review emphasizes the synthesis methods, modes of action under dissipative conditions and the various biomedical applications of AgNPs in detail.

Gold Nanoparticles Aggregation: Drastic Effect of Cooperative Functionalities in a Single Molecular Conjugate

2012 ◽  
Vol 116 (4) ◽  
pp. 2683-2690 ◽  
Author(s):  
Volodymyr Chegel ◽  
Oleksandre Rachkov ◽  
Andrii Lopatynskyi ◽  
Shinsuke Ishihara ◽  
Igor Yanchuk ◽  
...  
Keyword(s):  
Gold Nanoparticles ◽  
Drastic Effect ◽  
Molecular Conjugate
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