Facile Precursor for Synthesis of Silver Nanoparticles Using Alkali Treated Maize Starch

Impact of Starch Coating Embedded with Silver Nanoparticles on Strawberry Storage Time

The strawberry has a very short postharvest life due to its fast softening and decomposition. The goal of this research is to see how well a starch-silver nanoparticle (St-AgNPs) coating affects the physical, chemical, and microbiological qualities of strawberries during postharvest life. Additionally, the effect of washing with running water on silver concentration in coated strawberry fruit was studied by an inductively coupled plasma-optical emission spectrometer (ICP-OES). Furthermore, the shelf-life period was calculated in relation to the temperature of storage. Fourier transform infrared-attenuated total reflectance (FTIR-ATR), UV-Visible, and Transmission Electron Microscopic (TEM) were used to investigate the structure of starch-silver materials, the size and shape of AgNPs, respectively. The AgNPs were spherical, with an average size range of 12.7 nm. The coated samples had the lowest weight loss, decay, and microbial counts as compared to the uncoated sample. They had higher total acidity and anthocyanin contents as well. The washing process led to the almost complete removal of silver particles by rates ranging from 98.86 to 99.10%. Finally, the coating maintained strawberry qualities and lengthened their shelf-life from 2 to 6 days at room storage and from 8 to 16 days in cold storage.

A Green, Simple and Facile Way to Synthesize Silver Nanoparticles Using Soluble Starch. pH Studies and Antimicrobial Applications

Along with the progress of nanoscience and nanotechnology came the means to synthesize nanometric scale materials. While changing their physical and chemical properties, they implicitly changed their application area. The aim of this paper was the synthesis of colloidal silver nanoparticles (Ag-NPs by ultrasonic disruption), using soluble starch as a reducing agent and further as a stabilizing agent for produced Ag-NPs. In this context, an important parameter for Ag-NPs preparation is the pH, which can determine the particle size and stability. The physical-chemical behavior of the synthesized Ag-NPs (shape, size, dispersion, electric charge) is strongly influenced by the pH value (experiment being conducted for pH values in the range between 8 and 13). The presence of a peak located at 412 nm into the UV-VIS spectra demonstrates the presence of silver nano-spheres into the produced material. In UV/VIS spectra, we observed a specific peak for yellow silver nano-spheres located at 412 nm. Samples characterization was performed by scanning electron microscopy, SEM, energy-dispersive X-ray spectroscopy, EDX, Fourier-transform infrared spectroscopy, and FT-IR. For all Ag-NP samples, we determined the zeta and observed that the Ag-NP particles obtained at higher pH and have better stability. Due to the intrinsic therapeutic properties and broad antimicrobial spectrum, silver nanoparticles have opened new horizons and new approaches for the control of different types of infections and wound healing abilities. In this context, the present study also aims to confirm the antimicrobial effect of prepared Ag-NPs against several bacterial strains (indicator and clinically isolated strains). In this way, it was confirmed that the antimicrobial activity of synthesized Ag-NPs was good against Staphylococcus aureus (ATCC 25923 and S. aureus MSSA) and Escherichia coli (ATTC 25922 and clinically isolated strain). Based on this observation, we conclude that the prepared Ag-NPs can represent an alternative or auxiliary material used for controlling important nosocomial pathogens. The fungal reference strain Candida albicans was more sensitive at Ag-NPs actions (zone of inhibition = 20 mm) compared with the clinically isolated strain (zone of inhibition = 10 mm), which emphasizes the greater resistance of fungal strains at antimicrobial agent’s action.

Gold and silver nanoparticles used for SERS detection of S. aureus and E. coli

Surface enhanced Raman scattering (SERS) is emerging as a robust analytical method used in sensing applications in chemical as well as biological systems. SERS has been reported to be used in fast detection of micro-organisms up to the specificity of strain identification. However, use of SERS is tricky because of difficulties involved in selection of SERS active substrate so as to give uniform, sensitive as well as reproducible results. We have synthesized silver and gold nanoparticles using chemical, electrochemical and microwave-assisted methods followed by their characterization. Uses of these nanoparticles in association with micro-organisms such as S. aureus and E. coli have been analyzed using SERS to generate signature spectra. This demonstrates use of so synthesized gold and silver nanoparticles as SERS active substrates for rapid detection of micro-organisms which pave way to find applications in disease diagnostics.

Metal-dependent nano-catalysis in reduction of aromatic pollutants

Nanostructures have great potential in catalysis and their compositions may cause some interferences in the reactivity. Therefore, the present study focuses on comparison between three metallic nanoparticle-based Ag, Au, and Pd as nano-catalyst in reduction of aromatic pollutants. To neglect any interpenetration in their catalytic reactivity, the metallic nanoparticles were prepared via a consistent and reproducible one-step method with alkali-activated dextran. Interestingly, small sized/spherical AgNPs, AuNPs, and PdNPs were successively prepared with particle size of 3.4, 8.3, and 17.1 nm, respectively. The catalytic performance of the synthesized NPs was estimated for the reduction of p-nitroaniline and methyl red dye as different aromatic pollutants. Regardless of the particle size, there was a strong relation between catalytic action and the type of metal which followed the order of PdNP > AuNPs > AgNPs. Graphical Abstract.

High conversion synthesis of <10 nm starch-stabilized silver nanoparticles using microwave technology

A microwave reaction to convert 99 ± 1% of Ag+ to silver nanoparticles (AgNPs) of size <10 nm within 4.5 min with a specific production rate and energy input of 5.75 mg AgNP L-1 min-1 and 5.45 W mL-1 reaction volume was developed. The glucose reduced and food grade starch stabilized particles remained colloidally stable with less than a 4% change in the surface plasmon resonance band at 425-430 nm at t > 300 days. TEM determined the size of AgNPs, while TEM-EDS and XRD verified elemental composition. The conversion was determined by inductively coupled plasma atomic emission spectroscopy (ICP-AES) and thermal gravimetric analysis (TGA). Additionally, the required silver to starch input mass ratio, 1.0:1.3, to produce colloidally stabilized AgNPs is significantly reduced compared to previous studies. The antibacterial activity of freshly prepared AgNPs and AgNPs aged >300 days was demonstrated against E. coli as determined by agar diffusion assays. This result, corroborated by spectrophotometric and TEM measurements, indicates long-term colloidal stability of the product. Thus, this study sustainably produced antibacterial AgNPs from minimal inputs. In the broader context, the current work has quantified a sustainable platform technology to produce sphere-like inorganic nanoparticles with antimicrobial properties.

Nanosilver: new ageless and versatile biomedical therapeutic scaffold

Silver nanotechnology has received tremendous attention in recent years, owing to its wide range of applications in various fields and its intrinsic therapeutic properties. In this review, an attempt is made to critically evaluate the chemical, physical, and biological synthesis of silver nanoparticles (AgNPs) as well as their efficacy in the field of theranostics including microbiology and parasitology. Moreover, an outlook is also provided regarding the performance of AgNPs against different biological systems such as bacteria, fungi, viruses, and parasites (leishmanial and malarial parasites) in curing certain fatal human diseases, with a special focus on cancer. The mechanism of action of AgNPs in different biological systems still remains enigmatic. Here, due to limited available literature, we only focused on AgNPs mechanism in biological systems including human (wound healing and apoptosis), bacteria, and viruses which may open new windows for future research to ensure the versatile application of AgNPs in cosmetics, electronics, and medical fields.

In-situ deposition of Cu2O micro-needles for biologically active textiles and their release properties

Metal/metal oxide containing fibres are gradually increasing in textile industrialization recently, owing to their high potential for application as antimicrobial textiles. In this study, the reducing properties of cellulose were applied to synthesize cuprous oxide in-situ. The direct formation of Cu₂O on viscose fabrics was achieved via quite simple technique in two subsequent steps: alkalization and sorption. Cu contents in fabrics before and after rinsing ranged between 45.2-86.4mmol/kg and 18.1-67.7mmol/kg, respectively. Uniform micro-needles of Cu₂O were obtained with regular size and dimensions of 1.60±0.20μm in length and 0.13±0.03μm in width. Release of Cu^1+/2+ ions from selected samples was studied in water, physiological fluid and artificial sweat. Copper containing fabrics exhibited a percent of 96.8-97.8% and 85.5-89.0% for reduction in microbial viability, which was tested for S. aureus (as gram positive bacteria), E. coli (as gram-negative bacteria) and C. albicans and A. niger (as fungal species), respectively after 24h contact time.