Silver and zinc oxide nanoparticles (Ag and ZnO NPs) are widely used as antimicrobial agents. However, their potential toxicological impact on environmental microorganisms is largely unexplored. The aim of this work was to investigate the sensitivity and adaptability of five bacterial species isolated from sewage towards Ag and ZnO NPs. The bacterial species were exposed to increasing concentration of nanoparticles and the growth inhibitory effect, exopolysaccharides (EPSs) and extracellular proteins (ECPs) productions were determined. The involvement of surface charge in nanoparticles toxicity was also determined. The bacterial species were constantly exposed to nanoparticles to determine the adaptation behavior toward nanoparticles. The nanoparticles exhibited remarkable growth inhibitory effect on tested bacterial species. The toxicity of nanoparticles was found to be strongly dependent on surface charge effects. Though, these organisms are highly sensitive to Ag and ZnO NPs, the continuous exposure to these nanoparticles leads to moderate adaptation of bacterial species and the adapted bacterial species convert the highly toxic nano form to less toxic microform. Finally we predict that the continuing applications of nanoparticles in consumer products may lead to the development of nanoparticles resistant bacterial strains in future.

Bombyx mori silk fibers are an important biomaterial and are used in surgical sutures due to their remarkable biocompatibility. The major drawback to the application of biomaterials is the risk of bacterial invasion, leading to clinical complications. We have developed an easy and cost-effective method for fabrication of antibacterial silk fibers loaded with silver nanoparticles (AgNPs) by an in situ and ex situ process using an aqueous extract of Rhizophora apiculata leaf. Scanning electron microscopy revealed that well dispersed nanoparticles impregnated the silk fibers both in situ and ex situ. The crystalline nature of the AgNPs in the silk fibers was demonstrated by X-ray diffraction. The thermal and mechanical properties of the silk fibers were enhanced after they were impregnated with AgNPs. The silver-coated silk fibers fabricated by the in situ and ex situ method exhibited more than 90% inhibition against Pseudomonas aeruginosa and Staphylococcus aureus. Silk fibers doped with AgNPs were found to be biocompatible with 3T3 fibroblasts. The results obtained represent an important advance towards the clinical application of biocompatible AgNP-loaded silk fibers for prevention of surgical wound infections.

No abstract

An eco-friendly approach to the synthesis of silver nanoparticles (AgNPs) by extracellular components of Streptomyces albogriseolus has been reported. The isolated actinobacteria were genotypically identified by 16S rRNA sequencing analysis, and the morphology was observed by high-resolution scanning electron microscopy. The preliminary characterization of synthesized nanoparticles was carried out using ultraviolet-visible spectrophotometer. The maximum absorption spectra were found to be 409 nm at the 48th hour of incubation. The yield of AgNPs was found to be 72.64% as quantified by an atomic absorption spectrophotometer. The average size of AgNPs determined by the dynamic light scattering technique was 16.25 ± 1.6 nm. The results from transmission electron microscopy and X-ray diffraction confirmed the formation of spherical shaped and crystalline AgNPs. The interaction of protein with AgNPs was confirmed by Fourier transform infrared spectroscopy analysis. The biosynthesized AgNPs inhibited the growth of food pathogens (Bacillus cereus, Escherichia coli, and Staphylococcus aureus). Hence, the synthesis of AgNPs by S. albogriseolus could be employed as a probable antimicrobial agent to eliminate pathogenic microorganisms. This approach employed for the synthesis of nanoparticles paves a path for new biomaterial interfaces, which could be applied in different biomedical fields.

Development of eco-friendly processes for nanosynthesis is gaining importance owing to the widespread application of nanoparticles (NPs). In the present study, we have explained the mechanism and kinetics of bioreduction in the biosynthesis of silver nanoparticles (AgNPs) using aqueous leaf extract of Rhizophora apiculata. Spectrophotometric methods were employed to quantify the bioactive molecules present before and after the reduction process. The results showed that the polyphenols were the main components responsible for the biosynthesis of AgNPs, which was further confirmed by Fourier transform infrared spectroscopy. The kinetics of formation of AgNPs were monitored by time-resolved spectrophotometric and X-ray diffraction studies, which revealed that the NP formation is an autocatalytic process with a rate constant of 1.9 × 10(-2)  Min(-1) . The NPs were characterized using spectroscopic and microscopic techniques like ultraviolet-visible absorption spectroscopy, dynamic light scattering, transmission electron microscopy, scanning electron microscopy-energy-dispersive X-ray spectroscopy, and X-ray diffraction. The biogenic AgNPs showed substantial inhibitory activity to Proteus mirabilis, Pseudomonas aeruginosa, Escherichia coli, and Staphylococcus aureus with minimum inhibitory concentration values of 2.5, 12.5, 2.5, and 31.25 μg/mL, respectively. The current research provides an insight into the mechanistic aspects of bioreduction and formation of AgNPs.