Bio-mechanochemical synthesis of silver nanoparticles with antibacterial activity

By using a bio-mechanochemical approach combining mechanochemistry (ball milling) and green synthesis for the first time, silver nanoparticles (Ag NPs) with antibacterial activity were successfully synthesized. Concretely, eggshell membrane (ESM) or Origanum vulgare L. plant (ORE) and silver nitrate were used as environmentally friendly reducing agent and Ag precursor, respectively. The whole synthesis took 30?min in the former and 45?min in the latter case. The photon cross-correlation measurements have shown finer character of the product in the case of milling with Origanum. UV–Vis measurements have shown the formation of spherical NPs in both samples. TEM study has revealed that both samples are composites of nanosized silver nanoparticles homogenously dispersed within the organic matrices. It has shown that the size and size distribution of the silver nanoparticles is smaller and more uniform in the case of eggshell membrane matrix implying lower silver mobility within this matrix. The antibacterial activity was higher for the silver nanoparticles synthesized with co-milling with Origanum plant than in the case of milling with eggshell membrane.     

Synthesis and characterization of dextran-capped silver nanoparticles with enhanced antibacterial activity

Dextran-capped silver nanoparticles were synthesized by reducing silver nitrate with NaBH4 in the presence of dextran as capping agent. The characters of silver nanoparticles were investigated using UV-Vis spectrophotometer, nano-grainsize analyzer, X-ray diffraction, and transmission electron microscopy. Results showed that the silver nanoparticles capped with dextran were in uniform shape and narrow size distribution. Moreover, compared with polyvinylpyrrolidone (PVP)-capped silver nanoparticles, the dextran-capped ones possessed better stability. Antibacterial tests of these silver nanoparticles were carried out for Escherichia coli, Staphylococcus aureus, Staphylococcus epidermidis, Pseudomonas aeruginosa, and Klebsiella pneumoniae. Results suggested that the dextran-capped silver nanoparticles had high antibacterial activity against both Gram-positive and Gram-negative bacteria. In addition, the cytotoxicity in vitro of the dextran-capped silver nanoparticles was investigated using mouse fibrosarcoma cells (L929). The toxicity was evaluated by the changes of cell morphology and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide assay. Results indicated that these silver nanoparticles had slight effect on the survival and proliferation of L-929 cells at their minimal inhibitory concentration (MIC). After modified by dextran, the physiochemical properties of the silver nanoparticles had been improved. We anticipated that these dextran-capped silver nanoparticles could be integrated into systems for biological and pharmaceutical applications.     

One-step synthesis and characterization of anisotropic silver nanoparticles: application for enhanced antibacterial activity of natural fabric

A simple one-step chemical reduction method was employed for the synthesis of truncated triangular silver nanoparticles (Ag-NPs). The reduction of Ag ions by sodium borohydride was performed in the presence of poly(vinyl pyrrolidone) as a stabilizing agent. The synthesized Ag-NPs were characterized by UV–Vis spectroscopy, transmission electron microscopy, dynamic light scattering, FT-Raman spectrometer and X-ray diffraction in order to study optical, morphological, compositional, and structural properties. The UV–Vis spectrum showed three plasmon peaks located at 340, 412, and 700 nm, confirmed the anisotropic Ag-NPs. The average edge length of 22 ± 5 nm was observed from TEM images for truncated triangular Ag-NPs. From XRD pattern it was confirmed that the Ag-NPs were polycrystalline in nature, with preferential orientation along (111) lattice plane. The antibacterial susceptibility of Ag-NPs-treated fabrics were tested by Kirby–Bauer disk-diffusion test and American Association of Textile Chemists and Colorists (AATCC) test method 100-2004 against Gram-positive and Gram-negative bacteria. The Ag-NPs treated fabrics showed more pronounced antibacterial activity against Gram-negative bacteria than that of Gram-positive bacteria.     

Negligible particle-specific antibacterial activity of silver nanoparticles

For nearly a decade, researchers have debated the mechanisms by which AgNPs exert toxicity to bacteria and other organisms. The most elusive question has been whether the AgNPs exert direct "particle-specific" effects beyond the known antimicrobial activity of released silver ions (Ag(+)). Here, we infer that Ag(+) is the definitive molecular toxicant. We rule out direct particle-specific biological effects by showing the lack of toxicity of AgNPs when synthesized and tested under strictly anaerobic conditions that preclude Ag(0) oxidation and Ag(+) release. Furthermore, we demonstrate that the toxicity of various AgNPs (PEG- or PVP- coated, of three different sizes each) accurately follows the dose-response pattern of E. coli exposed to Ag(+) (added as AgNO(3)). Surprisingly, E. coli survival was stimulated by relatively low (sublethal) concentration of all tested AgNPs and AgNO(3) (at 3-8 μg/L Ag(+), or 12-31% of the minimum lethal concentration (MLC)), suggesting a hormetic response that would be counterproductive to antimicrobial applications. Overall, this work suggests that AgNP morphological properties known to affect antimicrobial activity are indirect effectors that primarily influence Ag(+) release. Accordingly, antibacterial activity could be controlled (and environmental impacts could be mitigated) by modulating Ag(+) release, possibly through manipulation of oxygen availability, particle size, shape, and/or type of coating.     

Green synthesis of silver nanoparticles using marine polysaccharide: Study of in-vitro antibacterial activity

The present contribution deals with one pot method for synthesis of silver nanoparticles through green route using sulfated polysaccharide isolated from marine red algae (Porphyra vietnamensis). The obtained silver nanoparticles showed surface plasmon resonance centered at 404 nm with average particle size measured to be 13 ± 3 nm. FTIR spectra revealed the involvement of sulfate moiety of polysaccharide for reduction of silver nitrate. The capping of anionic polysaccharide on the surface of nanoparticles was confirmed by zeta potential measurement (−35.05 mV) and is responsible for the electrostatic stability. The silver nanoparticles were highly stable at wide range of pH (2-10) and electrolyte concentration (up to 10⁻² M of NaCl). The dose dependent effect of synthesized silver nanoparticles revealed strong antibacterial activity against gram negative bacteria as compared to gram positive bacteria.     

Role of pH in the green synthesis of silver nanoparticles

The role of pH in the green synthesis of silver nanoparticles (AgNPs) is investigated. For the reduction synthesis of AgNPs we use silver nitrate, glucose, sodium hydroxide and starch respectively to serve as precursor, reducing agent, accelerator and stabilizer. The effect of NaOH addition on the nature of AgNPs is systematically studied. Two reaction pathways are proposed to explain the formation of AgNPs, keeping in view the pH changes that occur on addition of different amounts of NaOH. The aqueous sol of AgNPs prepared at different pH values display different surface plasmon resonance (SPR) behavior. This is explained in terms of size and size distribution of AgNPs.     

Green synthesis of silver nanoparticles using flower extract of Malva sylvestris and investigation of their antibacterial activity

High‐quality colloidal silver nanoparticles (AgNP) were synthesised via a green approach by using hydroalcoholic extracts of Malva sylvestris. Silver nitrate was used as a substrate ion while the plant extract successfully played the role of reducing and stabilising agents. The synthesised nanoparticles were carefully characterised by using transmission electron microscopy, atomic‐force microscopy, energy dispersive X‐ray spectroscopy, Fourier transform infrared spectroscopy and UV–vis spectroscopy. The maximum absorption wavelengths of the colloidal solutions synthesised using 70 and 96% ethanol and 100% methanol, as extraction solvents, were 430, 485 and 504 nm, respectively. Interestingly, the size distribution of nanoparticles depended on the used solvent. The best particle size distribution belonged to the nanoparticles synthesised by 70% ethanol extract, which was 20–40 nm. The antibacterial activity of the synthesised nanoparticles was studied on Escherichia coli, Staphylococcus aureus and Streptococcus pyogenes using disk diffusion, minimum inhibitory concentrations and minimum bactericidal concentrations assays. The best antibacterial activity obtained for the AgNPs produced by using 96% ethanolic extract.Inspec keywords: silver, nanoparticles, nanofabrication, antibacterial activity, colloids, particle size, transmission electron microscopy, atomic force microscopy, X‐ray chemical analysis, Fourier transform spectra, infrared spectra, ultraviolet spectra, visible spectra, microorganisms, nanomedicine, biomedical materialsOther keywords: Green synthesis, flower extract, Malva sylvestris, antibacterial activity, high‐quality colloidal silver nanoparticles, hydroalcoholic extracts, plant extract, reducing agents, stabilising agents, transmission electron microscopy, atomic‐force microscopy, energy dispersive X‐ray spectroscopy, Fourier transform infrared spectroscopy, UV– vis spectroscopy, colloidal solutions, particle size distribution, Escherichia coli, Staphylococcus aureus, Streptococcus pyogenes, disk diffusion, minimum inhibitory concentrations, minimum bactericidal concentrations assays, ethanolic extract, size 430 nm, size 485 nm, size 504 nm, size 20 nm to 40 nm, Ag     

Facile synthesis of silver nanoparticles mediated by polyacrylamide‐reduction approach to antibacterial application

The current time increase in the prevalence of antibiotic resistant ‘super‐bugs’ and the risks associated with food safety have become global issues. Therefore, further research is warranted to identify new and effective antimicrobial substances. Silver nanoparticles (Ag‐NPs) were synthesized by autoclaving technique using, different concentrations of Ag salt (AgNO₃) solution (1, 5, 10, and 25 mM). Their presence was confirmed by a surface plasmon resonance band at ∼435 nm using UV–Vis absorption spectra. The morphology of the synthesized Ag‐NPs stabilized by polyacrylamide (PAM) was examined by TEM, SAED, and EDS. TEM images revealed that the synthesized Ag‐NPs had an average diameter of 2.98±0.08 nm and SAED and EDS results confirmed the formation of Ag‐NPs. In addition, FT‐IR spectroscopy revealed that a PAM polymer matrix stabilized the Ag‐NPs. The well diffusion method, was used to test, Gram positive and Gram negative bacteria were examined. Also the minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) were studied against Ag‐NPs. The Ag‐NPs exhibited strong inhibitory activity, MIC and MBC against the tested clinical bacterial isolates. These results suggest that Ag‐NPs stabilized in PAM are highly effective against clinical bacterial isolates can be applied in medical fields.Inspec keywords: antibacterial activity, silver, nanoparticles, nanomedicine, surface plasmon resonance, X‐ray chemical analysis, transmission electron microscopy, electron diffraction, Fourier transform infrared spectroscopy, microorganisms, ultraviolet spectra, visible spectraOther keywords: Ag‐NP facile synthesis, PAM‐reduction approach, antibacterial application, antibiotic resistant super‐bugs, food safety, antimicrobial agents, antibiotics, antimicrobial substances, Ag salt solution concentration, ultraviolet‐visible absorption spectra, polyacrylamide, transmission electron microscopy, electron diffraction, energy dispersive X‐ray spectroscopy, TEM images, Fourier transform infrared spectroscopy, PAM polymer matrix, diffusion method, Gram positive bacteria, Gram negative bacteria, clinical bacterial isolates, Ag     

含纳米银的明胶/壳聚糖纳米纤维的制备及其抗菌性能研究

以浓度为88%的甲酸溶液作为纺丝溶剂,采用静电纺丝和紫外光照射还原的方法制备了含纳米银颗粒的明胶/壳聚糖纳米纤维。研究发现,壳聚糖的加入量低于明胶质量的3/16时可以得到纳米纤维,纤维平均直径随着硝酸银加入量的增大而减小,纤维表面纳米银的平均直径随着硝酸银加入量的增大而增大,在纺丝体系中硝酸银的加入量存在一个极限值。所制得含纳米银的明胶/壳聚糖纳米纤维对金黄色葡萄球菌和绿脓杆菌具有较好的抑菌性能,纺丝时加入1%硝酸银制得纳米纤维膜的抑菌率达到99%以上,这种抗菌型纳米纤维可以应用于医用敷料等领域。     

A facile method to prepare size-tunable silver nanoparticles and its antibacterial mechanism

The antibacterial effect of silver nanoparticles (denoted as Ag NPs) is closely related to size. This could partly explain why size controllable synthesis of Ag NPs for bactericidal application is drawing much attention. Thus, we establish a facile and mild route to prepare size-tunable Ag NPs with highly uniform morphologies and narrow size distributions. The as-prepared Ag NPs with averaged sizes of 2, 12 and 32?nm were characterized by transmission electron microscopy (TEM), ultraviolet–visible absorption spectroscopy (UV–vis), X-ray powder diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The antimicrobial effect of the as-prepared Ag NPs with different particles size was assessed by broth dilution and disk diffusion as well as measurement of optical density (OD₆₀₀). Moreover, their antibacterial mechanism was discussed in relation to morphology observation of microorganism by scanning electron microscopy (SEM) and to concentration detection of Ag⁺ by stripping voltammetry. It was found that the parameters such as reactant molar ratio, reaction time, dropping speed, and most of all, pH of the reactant solutions, have significant influences on size-regulation of Ag NPs. The as-prepared Ag NPs exhibit excellent antibacterial properties, and their antimicrobial activities increase with decreasing particles size. Besides, two kinds of mechanisms, i.e., contact action and release of Ag⁺, are responsible for the antimicrobial effect of Ag NPs.     

Synthesis of N-halamine-functionalized silica-polymer core-shell nanoparticles and their enhanced antibacterial activity

N-halamine-functionalized silica-polymer core-shell nanoparticles with enhanced antibacterial activity were synthesized through the encapsulation of silica nanoparticles as support with polymeric N-halamine. The as-synthesized nanoparticles were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy-dispersive x-ray spectrometry (EDX), dynamic light scattering (DLS), thermogravimetric analysis (TGA), and Fourier transform infrared (FTIR). These N-halamine-functionalized silica-polymer core-shell nanoparticles displayed powerful antibacterial performance against both Gram-positive bacteria and Gram-negative bacteria, and their antibacterial activities have been greatly improved compared with their bulk counterparts. Therefore, these N-halamine-functionalized silica-polymer core-shell nanoparticles have the potential for various significant applications such as in medical devices, healthcare products, water purification systems, hospitals, dental office equipment, food packaging, food storage, household sanitation, etc.     

Green synthesis of silver nanoparticles using Mentha pulegium and investigation of their antibacterial,antifungal and anticancer activity

A simple and eco‐friendly method for efficient synthesis of stable colloidal silver nanoparticles (AgNPs) using Mentha pulegium extracts is described. A series of reactions was conducted using different types and concentrations of plant extract as well as metal ions to optimize the reaction conditions. AgNPs were characterized by using UV–vis spectroscopy, transmission electron microscopy, atomic force microscopy, dynamic light scattering, zetasizer, energy‐dispersive X‐ray spectroscopy (EDAX) and Fourier transform infrared spectroscopy (FTIR). At the optimized conditions, plate shaped AgNPs with zeta potential value of ‐15.7 and plasmon absorption maximum at 450 nm were obtained using high concentration of aqueous extract. Efficient adsorption of organic compounds on the nanoparticles was confirmed by FTIR and EDAX. The biogenic AgNPs displayed promising antibacterial activity on Escherichia coli, Staphylococcus aureus, and Streptococcus pyogenes. The highest antibacterial activity of 25 µg mL‐1 was obtained for all the strains using aqueous extract synthesized AgNPs. The aqueous extract synthesised AgNPs also showed considerable antifungal activity against fluconazole resistant Candida albicans. The cytotoxicity assay revealed considerable anticancer activity of AgNPs on HeLa and MCF‐7 cancer cells. Overall results indicated high potential of M. pulegium extract to synthesis high quality AgNPs for biomedical applications.Inspec keywords: silver, nanoparticles, nanofabrication, botany, antibacterial activity, biomedical materials, nanomedicine, ultraviolet spectra, visible spectra, transmission electron microscopy, atomic force microscopy, X‐ray chemical analysis, Fourier transform infrared spectra, electrokinetic effects, microorganisms, cellular biophysics, cancerOther keywords: antibacterial activity, antifungal activity, anticancer activity, stable colloidal silver nanoparticle, Mentha pulegium, plant extract, UV‐visible spectroscopy, transmission electron microscopy, atomic force microscopy, DLS, zetasizer, energy‐dispersive X‐ray spectroscopy, Fourier transform infrared spectroscopy, methanolic extract, aqueous extract, plate‐shaped silver nanoparticle, zeta potential, plasmon absorption maximum, organic compounds adsorption, biogenic silver nanoparticle, Escherichia coli, Staphylococcus aureus, Streptococcus pyogenes, fluconazole‐resistant Candida albicans, MTT assay, HeLa cancer cell, MCF‐7 cancer cell, Ag     

Synthesis of oleic acid-stabilized silver nanoparticles and analysis of their antibacterial activity

The development of new and simple green chemical methods for synthesizing colloidal solutions of functional nanoparticles is desirable for environment-friendly applications. In the present work, we report a feasible method for synthesizing colloidal solutions of silver nanoparticles (Ag NPs) based on the modified Tollens technique. The Ag NPs were stabilized by using oleic acid as a surfactant and were produced for the first time by the reduction of silver ammonium complex [Ag(NH₃)₂]⁺_(aq) by glucose with UV irradiation treatment. A stable and nearly monodisperse aqueous Ag NPs solution with average-sized particles (~ 9–10 nm) was obtained. The Ag NPs exhibited high antibacterial activity against both Gram-negative Escherichia Coli (E. coli) and Gram-positive Staphylococcus aureus bacteria. Electron microscopic images and analyses provided further insights into the interaction and bactericidal mechanism of the Ag NPs. The proposed method of synthesis is an effective way to produce highly bactericidal colloidal solutions for medical, microbiological, and industrial applications.     

Enhanced antibacterial effect of silver nanoparticles obtained by electrochemical synthesis in poly(amide-hydroxyurethane) media

In the present study, we report enhanced antimicrobial properties of 29 and 23 nm silver nanoparticles (Ag NPs) obtained by electrochemical synthesis in poly(amide-hydroxyurethane) media. Antibacterial activity assessed by disk diffusion method indicates that silver nanoparticles produced inhibition zones for both Escherichia coli and Staphylococcus aureus depending on silver concentration. The bacterial growth curve performed in the presence of silver nanoparticles showed a stronger antibacterial effect at lower concentrations than those described in the earlier reports. The effect was both dose and size dependent and was more pronounced against Gram negative bacteria than Gram positive one. The smallest Ag NPs used had a bactericidal effect resulting in killing E. coli cells. Scanning electron microscopy analysis indicated major damage and morphology changes of the silver nanoparticles treated bacterial cells. The major mechanism responsible for the antibacterial effect probably consists in clusters formation and nanoparticles anchorage to the bacterial cell surface.     

Synthesis and antibacterial properties of silver nanoparticles

Nanometer sized silver particles were synthesized by inert gas condensation and co-condensation techniques. Both techniques are based on the evaporation of a metal into an inert atmosphere with the subsequent cooling for the nucleation and growth of the nanoparticles. The antibacterial efficiency of the nanoparticles was investigated by introducing the particles into a media containing Escherichia coli. The antibacterial investigations were performed in solution and on petri dishes. The silver nanoparticles were found to exhibit antibacterial effects at low concentrations. The antibacterial properties were related to the total surface area of the nanoparticles. Smaller particles with a larger surface to volume ratio provided a more efficient means for antibacterial activity. The nanoparticles were found to be completely cytotoxic to E. coli for surface concentrations as low as 8 microg of Ag/cm2.     

Green synthesis of silver nanoparticles using Glaucium corniculatum (L.) Curtis extract and evaluation of its antibacterial activity

The metal nanoparticles, due to interesting features such as electrical, optical, chemical and magnetic properties, have been investigated repeatedly. Also, the mentioned nanoparticles have specific uses in terms of their antibacterial activity. The biosynthesis method is more appropriate than the chemical method for producing the nanoparticles because it does not need any special facilities; it is also economically affordable. In the current study, the silver nanoparticles (AgNPs) were obtained by using a very simple and low‐cost method via Glaucium corniculatum (L.) Curtis plant extract. The characteristics of the AgNPs were investigated using techniques including: X‐ray diffraction, transmission electron microscopy (TEM), scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy. The SEM and TEM images showed that the nanoparticles had a spherical shape, and the mean diameter of them was 53.7 and 45 nm, respectively. The results of the disc diffusion test used for measuring the anti‐bacterial activity of the synthesised nanoparticles indicated that the formed nanoparticles possessed a suitable anti‐bacterial activity.Inspec keywords: silver, nanoparticles, antibacterial activity, nanomedicine, nanofabrication, X‐ray diffraction, transmission electron microscopy, scanning electron microscopy, Fourier transform infrared spectraOther keywords: green synthesis, silver nanoparticles, Glaucium corniculatum Curtis extract, antibacterial activity, metal nanoparticles, biosynthesis method, X‐ray diffraction, transmission electron microscopy, scanning electron microscopy, Fourier transform infrared spectroscopy, SEM, TEM, spherical shape, disc diffusion test, Ag     

Investigative evaluation of Cassia absus for antibacterial capacity and biomimetic synthesis of silver nanoparticles

Cassia absus is used for medicinal purposes for a long time all over the world. In this study, the authors report the antimicrobial potential of C. absus extracts obtained with different solvents. The extract(s) obtained with ethyl acetate yielded the best antibacterial effects because of a rich supply of oxalates and alkaloids in it. The same extract was also exploited for reducing Ag⁺ ions (to metallic Ag⁰) for the synthesis of nanoparticles. Electron microscopy revealed that the silver nanoparticles were ∼18–25 nm in diameter. The Fourier‐transform infrared evaluation pointed towards the fact that flavonoids present in the plant extract were acting as reductants while amino groups were the bound stabilisation agents to the synthesised nanoparticles limiting the diameter to a certain threshold and avoiding aggregation naturally. A comparative antibacterial assay of C. absus versus Ag nanoparticles showed that the nanoparticles as well as organic (ethyl acetate) extract of the plant checked the growth of selected (MDR) superbugs. However, the biosynthesised Ag nanoparticles returned better antibacterial efficacies than ethyl acetate extract.Inspec keywords: biomimetics, nanomedicine, nanoparticles, nanofabrication, reduction (chemical), microorganisms, silver, antibacterial activity, Fourier transform infrared spectra, biomedical materials, electron microscopyOther keywords: antibacterial capacity, biomimetic synthesis, silver nanoparticles, antimicrobial potential, ethyl acetate, oxalates, alkaloids, electron microscopy, Fourier‐transform infrared evaluation, antibacterial efficacies, antibacterial assay, organic extract, Cassia absus, flavonoids, Ag     

Medicinal plants mediated the green synthesis of silver nanoparticles and their biomedical applications

The alarming effect of antibiotic resistance prompted the search for alternative medicine to resolve the microbial resistance conflict. Over the last two decades, scientists have become increasingly interested in metallic nanoparticles to discover their new dimensions. Green nano synthesis is a rapidly expanding field of interest in nanotechnology due to its feasibility, low toxicity, eco‐friendly nature, and long‐term viability. Some plants have long been used in medicine because they contain a variety of bioactive compounds. Silver has long been known for its antibacterial properties. Silver nanoparticles have taken a special place among other metal nanoparticles. Silver nanotechnology has a big impact on medical applications like bio‐coating, novel antimicrobial agents, and drug delivery systems. This review aims to provide a comprehensive understanding of the pharmaceutical qualities of medicinal plants, as well as a convenient guideline for plant‐based silver nanoparticles and their antimicrobial activity.     

Zephyranthes candida flower extract mediated green synthesis of silver nanoparticles for biological applications

The development of biologically active nanoparticles (NPs) has played a prominent role in medicinal, pharmaceuticals and bio-nanotechnology fields. Phytosynthesis is a simple, reproducible, and effective method to produce highly stable metal nanoparticles. In this present work, silver (Ag) nano particles (NPs) were produced using Zephyranthes candida (Z. candida) flower extract as a sustainable, cost-effective, and non-hazardous stabilizing agent. In the view of X-ray diffraction (XRD) analysis, the face centred cubic structure of Ag NPs was revealed. From the UV–Vis spectral analysis, the formations of Ag NPs were further confirmed through surface plasmon resonance (SPR) at the highest absorbance (λ_max) of 418 nm. FT-IR represents the spectra that reveal the presence of diverse functional groups along with their vibrational modes present in Ag NPs and Z.candida flower extract. SEM and TEM denote the formation of spherical morphology of Ag NPs. Furthermore, EDX and XPS spectra confirmed the purity of the prepared Ag NPs. Finally, the biological studies such as anti-inflammatory, anti-diabetic, anti-oxidant, anticancer confirm the bioactivity of the synthesized Zephyranthes Candida mediated Ag NPs.