AgNPs Solution Research Articles

Silver nanoparticles in building materials for environment protection against microorganisms

Gypsum and grout are finishing materials found in almost all constructions. Specifically, gypsum has been widely used because of its low cost in the composition of drywall. However, in humid environments, they are susceptible to microorganism infestation. In this work, silver nanoparticles (Ag-NPs) were incorporated to gypsum (643 and 321 ppm) and grout (227 ppm) and the antimicrobial activity tested. The MIC value for Ag-NPs solution was 26.8 µg ml−1 for Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli and 428 µg ml−1 for the A. Niger. Another MIC test with specimen component dilutions indicated that grout and gypsum do not exhibit antibacterial activity against S. aureus. However, when incorporated with Ag-NPs, both grout and gypsum demonstrate growth inhibition. In a biofilm test performed with S. aureus, SEM images revealed crenation of bacteria in contact with specimens containing Ag-NPs. The addition of Ag-NPs causes change in color that was measured through CIELAB (International Commission on Illumination) color coordinates. There is no difference in the L value parameter (lightness) for all materials tested. However, the comparison between the parameters a (green–red coordinate) and b (blue–yellow) for gypsum and grout results in a statistically significant difference (p < 0.05, Kruskal). The values of b increase as the Ag-NPs concentration increases because of the yellowish coloration of the solution. It can be concluded that Ag-NPs can be incorporated to gypsum and grout, maintaining its antimicrobial feature improving the material properties, which can benefit health and the environment.

Evaluating internal standards for the determination of gas phase mercury using silver nanoparticle assisted total reflection X-ray fluorescence

Mercury was often used to protect cultural heritage specimens from damage by various pests. Over time, mercury is released into the air and access to archives may therefore need to be controlled due to the hazards associated with high gas phase concentrations of Hg. A procedure to analyze gas phase Hg using total reflection X-ray fluorescence (TXRF) was developed. TXRF is a small footprint instrument available in many laboratories. Silver nanoparticles (AgNPs) were prepared and used to sample Hg from air directly on the quartz carriers. The relative standard deviation (RSD) for the AgNP amount deposited on the carriers was on average about 10%. The efficiency and reproducibility of the Hg-capture on washed and non-washed AgNP-specimens was studied. Washed carriers had about 60% less Ag than non-washed specimens. Interestingly, the amount of Hg captured on washed carriers was significantly higher than on non-washed carriers. Calibration in TXRF is usually achieved using an internal standard (IS). However, acidic IS solutions like gallium (3% HNO3) led to the formation of large Ag crystals and a rather poor reproducibility was observed for Ag determination using Ga as IS i.e. 10%. Alternative standard solutions having basic to neutral pH (i.e. chromate and molybdenum) were therefore tested. The TXRF results showed good reproducibility using Mo (L-lines) as IS, yielding a RSD of 2.6% mixing the standard with the AgNP solution before carrier preparation. A lower reproducibility was obtained using Cr as IS with a RSD of 4.0%. Micro-X-ray fluorescence studies on the spatial distribution of Mo and Ag in AgNP deposits with Mo IS showed a relatively even distribution of both elements over the entire area of the residue, although neither element correlated pixel by pixel. A web-like structure of Mo was overlaid by a space-filling Ag distribution, resulting in poor correlation (r = 0.59). The spatial distribution of Ag and Cr in AgNP deposits with Cr IS showed a significant inhomogeneity on a larger length scale. Half of the deposit was usually richer in Cr than the other half, however, the correlation (r = 0.77) was higher than for AgNPs with Mo IS. The addition of Mo to an already dried and washed AgNP deposits resulted in a more inhomogeneous sample (r = 0.27).

Effects of Silver Nanoparticles on the Activities of Soil Enzymes Involved in Carbon and Nutrient Cycling

Soils are continuously exposed to large amounts of engineered nanoparticles, especially silver nanoparticles (AgNPs), which can affect the activity, stability, and specificity of microbial enzymes. Therefore, the measurement of specific enzyme activity can be used to identify major changes in soil environments. Accordingly, the aim of the present study was to investigate the effects of AgNPs on soil enzymes that play critical roles in mineralizing carbon and nutrients in soil. Soil samples (silt loam and sandy loam) were collected from the surface layer (0–15 cm) of a field at the George Washington Carver Farm, Lincoln University of Missouri, USA. The soils were then treated with AgNP solutions at 0, 1 600, or 3 200 μg Ag kg−1 dry soil, using either 10- or 50-nm AgNPs and a randomized complete block design, with three replicates per treatment. The AgNP-treated soil samples were homogenized and incubated for one month, and soil acid phosphatase, β-glucosaminidase, β-glucosidase, and arylsulfatase activities were measured after one hour, one week, and one month of incubation. The activities of all four enzymes were reduced by AgNP treatment after one hour and one week. However, AgNP size had no effect. After one month of incubation, the AgNP treatments had mixed effects, which suggests that soil enzymes are only affected on a short-term basis. Further studies are required to determine the mechanisms by which AgNPs reduce soil enzyme activity.

Bio-inspired immobilization of casein-coated silver nanoparticles on cellulose acetate membranes for biofouling control

This study shows the results of low-biofouling nanocomposite membranes, loaded with casein-coated silver nanoparticles (casein-Ag-NPs). Membranes were cast and imbedded with Ag-NPs using two approaches, physical blending of Ag-NPs in the dope solution (PAg-NP/CA membranes) and chemical attachment of Ag-NPs to cast membranes (CAg-NP/CA membranes), to determine their biofouling control properties. The functionalization of Ag-NPs onto the CA membranes was achieved via attachment with functionalized thiol groups with the use of glycidyl methacrylate (GMA) and cysteamine chemistries, which was inspired by the affinity of silver to the thiol groups of cysteine proteins in bacteria. The immobilization chemistry successfully prevented leaching of silver nanoparticles during cross-flow studies. Pseudomonas fluorescens Migula in brackish water was used for dead-end filtration, where CAg-NP/CA membranes displayed lower a significant reduction in the accumulation of bacterial cells, likely due to the more dispersed nanoparticles across the surface.

Determination of mercury (II) ions based on silver-nanoparticles-assisted growth of gold nanostructures: UV–Vis and surface enhanced Raman scattering approaches

Innovative dual detection methods for mercury(II) ions (Hg(II)) have been developed based on the formation of gold nanostructures (AuNSs) following the addition of mercury-containing solution to a mixture containing an optimized amount of Au(III), H2O2, HCl, and silver nanoparticles (AgNPs). In the absence of Hg(II), the addition of Au(III), H2O2, and HCl to the AgNP solution changes the solution's color from yellow to red, and the absorption peak shifts from 400 to 526nm, indicating the dissolution of AgNPs and the formation of gold nanoparticles (AuNPs). Because of the spontaneous redox reaction of Hg(II) toward AgNPs, the change in the amount of remaining AgNP seed facilitates the generation of irregular AuNSs, resulting in changes in absorption intensity and shifting the peak within the range from 526 to 562nm depending on the concentration of Hg(II). Under optimal conditions, the limit of detection (LOD) for Hg(II) at a signal-to-noise ratio (S/N) of 3 was 0.3μM. We further observed that AgNP-assisted catalytic formation of Au nanomaterials deposited on a surface enhanced Raman scattering active substrate significantly reduced the Raman signal of 4-mercaptobenzoic acid, dependent on the Hg(II) concentration. A linear relationship was observed in the range 0.1nM–100μM with a LOD of 0.05nM (S/N 3.0). As a simple, accurate and precise method, this SERS-based assay has demonstrated its success in determining levels of Hg(II) in real water samples.

A monodisperse anionic silver nanoparticles colloid: Its selective adsorption and excellent plasmon-induced photodegradation of Methylene Blue

To address the pollution problem of organic dyes, monodispersed anionic silver nanoparticles (AgNPs) with an average size of 6 nm were prepared in water media via chemical reduction method from oleic acid and n-butyl amine. The aqueous solution of the resultant AgNPs was utilized as a photocatalyst to investigate the adsorption and photodegradation behaviors of organic dyes under different light irradiation. The morphology and surface characteristics of the synthesized AgNPs were probed using TEM, XRD, FTIR and zeta potential analysis. The adsorption and degradation process of organic dyes on the AgNPs were characterized in details by UV–Vis spectrophotometer. The results showed that the AgNPs exhibited a characteristic charge- and size-selective adsorption of dyes owing to the profoundly negative charged surface, which enables the AgNPs to possess high selective degradation of Methylene Blue. More still, due to the surface plasmon resonance (SPR) effect of AgNPs, the obtained AgNPs presented a higher photocatalytic activity to Methylene Blue under UV light, visible light, and solar light compared with commercial photocatalysts. The 5 cyclic reactions revealed its high stability and reusability. In a nutshell, the proposed mechanism systematically combined the selective adsorption and the SPR effect to explain the detailed photocatalytic process of the obtained AgNPs.

Antibacterial properties of silver nanoparticles as a root canal irrigant against Enterococcus faecalis biofilm and infected dentinal tubules.

To evaluate the antimicrobial action of an irrigant containing silver nanoparticles in an aqueous vehicle (AgNp), sodium hypochlorite and chlorhexidine against Enterococcus faecalis biofilm and infected dentinal tubules. Bovine dentine blocks were used for E.faecalis biofilm development for 21days and irrigated with 94ppm AgNp solution, 2.5% NaOCl and 2% chlorhexidine for 5, 15 and 30min. For infection of dentinal tubules with E.faecalis, dentine specimens from bovine incisors were submitted to a contamination protocol over 5days, with eight centrifugation cycles on every alternate day, and irrigated with the same solutions and time intervals used for the biofilm. The specimens were stained with the Live/Dead technique and evaluated using a confocal laser scanning microscope (CLSM). The bioImage_L software was used for measurement of the total biovolume of biofilm in μm3 and percentage of viable bacteria (green cells) in biofilm and in dentinal tubules found after the irrigation. Statistical analyses were performed using Kruskal-Wallis and Dunn's tests for quantification of viable cells in biofilm, the Friedman test for comparisons of viable bacteria in dentinal tubules in different areas of the root canal and the Mann-Whitney U-test to compare the action of the irrigants between the two methods (P<0.05). The AgNp solution eliminated fewer bacteria, but was able to dissolve more biofilm compared with chlorhexidine (P<0.05). NaOCl had the greatest antimicrobial activity and biofilm dissolution capacity. AgNp solution had less antimicrobial action in infected dentinal tubules compared with NaOCl (P<0.05). The AgNp solution after 5min was more effective in eliminating planktonic bacteria in dentinal tubules than in biofilm, but at 30min fewer viable bacteria were observed in the biofilm compared with intratubular dentine (P<0.05). AgNp irrigant was not as effective against E.faecalis compared to solutions commonly used in root canal treatment. NaOCl is appropriate as an irrigant because it was effective in disrupting biofilm and in eliminating bacteria in biofilms and in dentinal tubules.

Effectiveness of nanoparticles solutions and conventional endodontic irrigants against Enterococcus faecalis biofilm.

To overcome the challenge imposed by the presence of biofilm and reach significant bacterial reduction of the root canals, many irrigants have been indicated during endodontic treatment, among them nanoparticles solutions. This study aims to evaluate the effectiveness of experimental solutions containing silver and zinc oxide nanoparticles (ZnO Np) and conventional endodontic irrigants against Enterococcus faecalis biofilm, in root canals. Seventy-six extracted human teeth were biomechanically prepared and sterilized. The root canal surface was exposed to E. faecalis suspension to form a 7-day-old biofilm. Four teeth were analyzed by scanning electron microscopy (SEM) to confirm the presence of biofilm. The remaining teeth were randomly divided into 6 groups (n = 12) and treated with passive ultrasonic irrigation and different solutions: G1 - 0.85% saline (control); G2 - 2% chlorhexidine gluconate (CHX); G3 - 5% sodium hypochlorite (NaOCl); G4 - 1% NaOCl; G5 - 1% silver nanoparticles (Ag Np) solution; and G6 - 26% ZnO Np solution. The susceptibility of E. faecalis biofilms to disinfecting solutions (n = 10) was determined by quantification of colony-forming units. SEM analysis was also carried out to examine the biofilm structure after treatments (n = 2). Data were analyzed by Kruskal-Wallis and Dunn post hoc tests (P < 0.05). All tested solutions showed superior effectiveness compared to 0.85% saline (P < 0.05). Overall, 2% CHX presented the most effective action against E. faecalis biofilm, followed by 5% NaOCl, 1% Ag Np, 26% ZnO Np, and 1% NaOCl. 1% Ag Np and 26% ZnO Np were effective against E. faecalis biofilm similarly to conventional endodontic irrigants.

Ferulic acid promoted in-situ generation of AgNPs@silk as functional colorants

A rapid, green and simple procedure for the in-situ generation of AgNPs@silk as functional colorant is described herein. Silver (Ag+) ions were first diffused into the silk fabric matrix by soaking into aqueous AgNO3 solution, subsequently, alcoholic solution of ferulic acid, a natural polyphenol, was added as an eco-friendly reductant for the generation of AgNPs@silk. The formation of AgNPs was confirmed by visible color changes and UV–visible absorption spectra. The residual AgNPs solution was characterized via UV–visible spectroscopy, TEM and DLS. The UV–visible spectra and TEM analyses confirmed the formation of more or less spherical well-dispersed AgNPs. The AgNPs@silk was characterized by SEM, EDS, XRD, XPS and FTIR. The Ag content of AgNPs@silk was determined by nitric acid digestion followed by ICP-OES. The color, antibacterial and UV protection characteristics of AgNPs@silk were also evaluated. AgNPs@silk produced a beautiful color pallete ranging from light creamish brown to dark golden brown. The AgNPs treated silk exhibited outstanding antibacterial activity (>99% bacterial reduction) and excellent laundering durability, where it inhibited >94% of E. coli even after 10 washing cycles. Moreover, AgNPs@silk was highly effective blocking of UV radiation in both UVA and UVB regions, and thus offered excellent UV protection.

Antiviral Activity Effect of Silver Nanoparticles (Agnps) Solution Against the Growth of Infectious Bursal Disease Virus on Embryonated Chicken Eggs with Elisa Test

Infectious bursal disease virus is one of the strategic infectious disease in Indonesia. Despite disinfection and vaccination technology has been doing, the cases still frequently occur and it needs another alternative technology to be developed to against IBD virus. This research try to answer the problem, it examines the effect of antiviral activity of silver nanoparticles (AgNPs) solution against the growth of infectious bursal disease virus in embryonated chicken eggs with ELISA Test. The research has two methods, the first method is conducted by mixing a solution of AgNPs and IBD Virus, two hours before inoculated (preventive method) and the second method is the virus inoculated first, 48 hours later the AgNPs solution injected (therapy method). Each method has several dosage of AgNPs solution respectively 0 ppm (positive control 20 ppm, 40 ppm, and 50 ppm). Virus samples taken from the choriallantoic membrane (CAM) and the embryo by crushed method. Results based on the value of OD (optical density) ELISA Test and Statistical Test ANOVA General Linier Models Univariate with Post-Hoc Duncan 5%, both methods have no significant difference (p&gt;0.05), it means the solution of AgNPs has good preventative and therapeutic characteristic. The mean of OD values also showed dosage of 20ppm is most effective dosage in against the growth of the virus, the dosage has significant difference (p&lt;0.05). The decreasing amount of virus in CAM and in embryos were not significantly different (p&gt;0.05), in both CAM and embryo AgNPs solution has good antiviral properties. Keywords : Silver Nanoparticles, Antiviral, Infectious Bursal Disesase, ELISA, Embryonated Chicken Eggs

Highly selective and ecofriendly colorimetric method for the detection of iodide using green tea synthesized silver nanoparticles

In this work, a simple, selective, sensitive and inexpensive colorimetric sensor has been developed for the detection of iodide ions using green tea (Camellia sinensis) synthesized silver nanoparticles (tea-capped AgNPs). The mechanistic route relied upon the binding of iodide ions to the surface of biosynthesized AgNPs. This binding led to decolorize the yellow color of AgNPs solution along with the disappearance of characteristic surface plasmon (SPR) band at 405nm. The mechanism of interaction of iodide with AgNPs has been discussed by using transmission electron microscopy (TEM) and differential pulse voltammetry (DPV). The biosynthesized AgNPs were capable of detecting iodide in the range from 1×10−7–2.5×10−5M, which exhibited good linear relationships between concentration and absorption change with the correlation coefficient (R2) of 0.994. The detection limit obtained by this tea-capped AgNPs was 6.5×10−8M which is comparable or some better than those obtained by previously reported chemical reduction methods. Moreover, the tea-capped AgNPs demonstrated a selective colorimetric response for iodide in the presence of other potential interfering ions like Br−, F−, Cl−, CH3COO−, NO2−, NO3−, H2PO4− and SO4−. Compared to other colorimetric methods designed for the detection of iodide ions, the proposed method has combined the features of good sensitivity and selectivity, and environment-friendly and cost-effective nature. More importantly, the method does not require any additional chemicals and specific reaction condition.

A novel wound dressing based on a Konjac glucomannan/silver nanoparticle composite sponge effectively kills bacteria and accelerates wound healing

A novel Konjac glucomannan/silver nanoparticle (KGM/AgNP) composite sponge was successfully prepared via a simple 2-step method for biomedical applications as wound-healing materials. First, AgNPs were prepared with green deoxidizer egg white. Then, KGM powder was added to the AgNP solution and stirred vigorously, and the composite sponge was obtained by freeze-drying. The KGM/AgNP composite sponge showed excellent water absorption and water retention, and considerable mechanical properties. KGM/AgNP composite sponges displayed good antibacterial activity against test microorganisms. In vitro cytocompatibility testing showed that L929 cells could survive well in the presence of KGM/AgNPs, indicating that KGM/AgNPs have good cytocompatibility. Animal models showed that the KGM/AgNP composite sponges effectively accelerated wound healing, and histological findings showed that they promoted fibroblast growth and accelerated epithelialization. The experimental results showed that KGM/AgNP composite sponges have great potential in promoting wound healing.

Ultra-rapid catalytic degradation of 4-nitrophenol with ionic liquid recoverable and reusable ibuprofen derived silver nanoparticles.

This study reports a one-pot and eco-friendly method for the synthesis of spherical ibuprofen derived silver nanoparticles (IBU-AgNPs) in aqueous media using ibuprofen analgesics drug as capping as well as reducing agent. Formation of AgNPs occurred within a few min (less than 5min) at room temperature without resorting to any harsh conditions and hazardous organic solvents. Synthesized AgNPs were characterized with common analytical techniques. Transmission electron microscope (TEM) images confirmed the formation of spherical particles having a size distribution in the range of 12.5±1.5nm. Employment of IBU analgesic aided the control of better size distribution and prevented agglomeration of particles. Such AgNPs solution was highly stable for more than two months when stored at ambient temperature. The IBU-AgNPs solution showed excellent ultra-rapid catalytic activity for the complete degradation of toxic 4-nitrophenol (4-NPh) into non-toxic 4-aminophenol (4-APh) within 40s. AgNPs were recovered with the help of water insoluble-room temperature ionic liquid and reused with enhanced catalytic potential. This method provides a novel, rapid and economical alternative for the treatment of toxic organic pollutants to maintain water quality and environmental safety against water pollution. It is extendable for the control of other reducible contaminants in water as well. Furthermore, this catalytic activity for an effective degradation of organic toxins is expected to play a crucial role for achieving the Sustainable Development Goal 6 set by United Nations.

Antibiofilm Efficacy of Positively Charged Imidazolium-Based Silver Nanoparticles in Enterococcus faecalis Using Quantitative Real-Time PCR

Background: Nanoparticles are made by different methodologies, which can affect the particle’s features. Recently, imidazolium-coated silver nanoparticles with a positive surface charge (PC Im-based AgNPs) have revealed favorable results as a root canal disinfectant. However, the antibacterial potency of these particles against biofilm form of Enterococcus faecalis, as the most resistant organism to eliminate in endodontic treatment, has not been investigated. It can be noted that removing this microorganism is associated with extremely effective disinfection. Objectives: This study investigated the antibacterial efficacy of PC Im-based AgNPs at 5.7 × 10-8 mol L-1 in comparison with 2.5% sodium hypochlorite (NaOCl) and 2% chlorhexidine as the two broadly used endodontic irrigation solutions against biofilm E. faecalis using quantitative real-time polymerase chain reaction. Methods: In total, 48 premolar teeth with a single root were infected with E. faecalis and then prepared with ProTaper rotary instruments. The samples were randomly allocated into 4 groups of 12 samples. Sterile saline, PC Im-based AgNPs, NaOCl, and chlorhexidine were used as irrigants. Sampling the root canals was implemented with paper points and Gates-Glidden drills. The reduction in E. faecalis counts was calculated and statistically analyzed by means of the Kruskal-Wallis and Mann-Whitney U tests. Results: Irrigation with PC Im-based AgNPs or NaOCl was significantly more effective in bacterial count reduction compared to irrigation with chlorhexidine or sterile saline (P 0.001). Conclusions: The PC Im-based AgNP solution revealed promising results as a root canal irrigant. This solution at 5.7 × 10-8 mol L-1 was effectively able to eliminate biofilm E. faecalis and this was not significantly different from that of 2.5% NaOCl.

Colorimetric detection of glutathione based on phthalic acid assisted synthesis of silver nanoparticles

A new rapid, sensitive and selective colorimetric sensing platform for the detection of glutathione (GSH) in dietary supplements was developed by phthalic acid (PTA) assisted synthesis of silver nanoparticles (AgNPs). The di-carboxylic functional groups of PTA were used to modify the surface of AgNPs. The resulting AgNPs product was characterized by surface plasmon resonance (SPR) Ultraviolet–visible spectroscopy (UV–vis), Zeta potential analyzer, Fourietransform infrared spectroscopy (FT-IR), Transmission electron microscopy (TEM) and X-ray diffraction analysis (XRD) techniques, demonstrated that PTA is an effective capping agent to stabilize AgNPs. AgNPs stabilized with PTA could cause the strong affinity to GSH. As the GSH concentration increased, the color of AgNPs solutions was gradually changed from yellow to orange and light purple as well as the SPR shifted from 400nm to 556nm upon an aggregation of AgNPs due to electrostatic interaction. The proposed colorimetric sensor was exhibited a linear response in the range of 0.1–100nM (R2=0.9992), with low detection limit (LOD) of 0.16±0.01nM. The sensor showed better precision with relative standard deviation (RSD) of 2.10% and 1.13% for ten repetitive measurements of 25nM and 75nM GSH solution, respectively. The sensitivity of AgNPs for GSH detection can be clearly differentiated towards other coexisting substances (Fe3+, Zn2+, Cu2+, K+, Ca2+, Mg2+, glucose, sucrose, cysteine, ascorbic acid and citric acid). The AgNPs colorimetric sensor could discriminatively detect GSH in dietary supplement samples with the recoveries values in the range of 98.5%–103.0%.

Silver nanoparticles enhance wound healing in zebrafish (Danio rerio)

Silver nanoparticles (AgNPs) were successfully synthesized by a chemical reduction method, physico-chemically characterized and their effect on wound-healing activity in zebrafish was investigated. The prepared AgNPs were circular-shaped, water soluble with average diameter and zeta potential of 72.66 nm and −0.45 mv, respectively. Following the creation of a laser skin wound on zebrafish, the effect of AgNPs on wound-healing activity was tested by two methods, direct skin application (2 μg/wound) and immersion in a solution of AgNPs and water (50 μg/L). The zebrafish were followed for 20 days post-wounding (dpw) by visual observation of wound size, calculating wound healing percentage (WHP), and histological examination. Visually, both direct skin application and immersion AgNPs treatments displayed clear and faster wound closure at 5, 10 and 20 dpw compared to the controls, which was confirmed by 5 dpw histology data. At 5 dpw, WHP was highest in the AgNPs immersion group (36.6%) > AgNPs direct application group (23.7%) > controls (18.2%), showing that WHP was most effective in fish immersed in AgNPs solution. In general, exposure to AgNPs induced gene expression of selected wound-healing-related genes, namely, transforming growth factor (TGF-β), matrix metalloproteinase (MMP) −9 and −13, pro-inflammatory cytokines (IL-1β and TNF-α) and antioxidant enzymes (superoxide dismutase and catalase), which observed differentiation at 12 and 24 h against the control; but the results were not consistently significant, and many either reached basal levels or were down regulated at 5 dpw in the wounded muscle. These results suggest that AgNPs are effective in acceleration of wound healing and altered the expression of some wound-healing-related genes. However, the detailed mechanism of enhanced wound healing remains to be investigated in fish.

Biothiols induced colour change of silver nanoparticles: A colorimetric sensing strategy

A sensor for the detection and determination of bio-thiols (glutathione (GSH) and cysteamine (Cyste)) has been developed by integrating the distinguished distance related optical characteristics of silver nanoparticles with the simplicity of colorimetric technique. In presence of these analytes, shift in surface plasmon resonance (SPR) absorption of silver nanoparticles (AgNPs) with change in its colour was observed. Yellow coloured AgNPs solution becomes colourless in presence of GSH and changes to red in presence of Cyste. FTIR, TEM and DLS studies were used to confirm the mechanism. The difference in absorption of AgNPs in the absence and presence of GSH was found to vary linearly in the range 1.00×10−5M to 5.00×10−7M concentration range with limit of detection at 3.68×10−7M. The method can also be applied to quantify Cyste in the range 1.10×10−6M to 5.00×10−8M with limit of detection at 1.80×10−8M. The utility of the proposed colorimetric assay is validated by determination of GSH and Cyste in artificial blood serum.

Characterization and in vitro antibacterial activity of saponin-conjugated silver nanoparticles against bacteria that cause burn wound infection.

Saponins are glycosides, which destabilize the membrane by altering the membrane permeability. Thus, the present study was aimed to fabricate the silver nanoparticles (AgNPs) using fenugreek derived saponin (SN) against multi-drug resistant bacteria. This study has optimized the concentration of SN (240mg/mL) for the synthesis of an effective AgNPs against the test organism Escherichia coli. The SN reduced AgNPs produced a reddish-brown colour and displayed UV absorption at 416nm. The bio-reducing efficiency of SN (62.76%) was calculated from the HPLC quantitation of free SN in the colloidal solution of AgNPs. The FESEM-EDAX analysis of SN-AgNPs revealed a spherical shape and showed signals for elemental silver along with carbon and oxygen. The spherical morphology of SN-AgNPs was also confirmed from its TEM and AFM micrographs and their sizes were found in between 2-15nm. The hydrodynamic size, zeta potential and crystalline nature of SN-AgNPs were studied by DLS and XRD analyses and were found to be 9-30nm, -18mV and fcc crystallinity respectively. The FT-IR analysis of SN-AgNPs revealed that the functional groups such as C-O, C=C, C=O and O-H of SN are involved in the reduction and stability of AgNPs. The SN-AgNPs have depicted a notable in vitro structural stability and showed a remarkable antibacterial activity against the bacterial species, related to severe burn wound infections. In conclusion, the findings of our study clearly demonstrate that the SN-AgNPs conjugate would be a novel effective antibacterial agent for the prevention/eradication of multi-drug resistant bacterial infections in severe burn wounds.

Eco-friendly microwave-enhanced green synthesis of silver nanoparticles using Aloe vera leaf extract and their physico-chemical and antibacterial studies

AbstractSilver nanoparticles (AgNPs) were synthesized usingAloe veraleaf extract as both reducing and stabilizing agentsviamicrowave irradiation method. The effects of the microwave exposure time and the amount of AgNO3solution on the mean particle size and concentration of the synthesized AgNPs solution were investigated using response surface methodology. The synthesized AgNPs were characterized by transmission electron microscopy, UV-Vis spectroscopy, and dynamic light scattering. Well-dispersed and spherically fabricated AgNPs with mean particle size (46 nm) and maximum concentration (64 ppm) and zeta potential (+15.5 mV), were obtained at optimal synthesis conditions, using 9 ml of AgNO3(1 mm) and 0.1 ml ofAloe veraextract during microwave exposure time of 360 s. The antibacterial activity of the synthesized AgNPs was tested usingEscherichia coliandStaphylococcus aureusbacteria and the obtained results indicated their significant inhibitory effects against these two Gram-negative and Gram-positive bacteria.

Colorimetric detection of tyrosinase during the synthesis of kojic acid/silver nanoparticles under illumination

We report a green, reliable and single-step colorimetric assay for tyrosinase (Tyr) using the silver nanoparticles (AgNPs) as the signal readout. With the aid of light as the catalyst, kojic acid can rapidly reduce Ag+ ions and stablize the produced AgNPs. While uopn addition of Tyr during the synthesis of AgNPs, Tyr can effectively interrupt the formation of AgNPs due to its preferential combination with kojic acid, eventually leading to color fading and signal decrease of AgNPs solution. The presented method shows a good linear response toward Tyr over the range 0.5–4u/mL with low detection limit of 0.117u/mL. Common coexisting substances including metal ions, amino acids and biomacromolecules exert no effect on the determination of Tyr. This colorimetric sensor was successfully employed to quantify Tyr in human serum samples.