Search

Silver nanoparticles (AgNPs) have been widely studied due to their interesting physicochemical properties and remarkable antibacterial properties. Chemical synthesis methods, including green chemistry, have achieved 0D nanostructures. However, ecological methods have little studied self-assembling Ag nanostructures, such as flowers or dendrites. In this work, Ag dendrites and Ag flower-like morphologies have been successfully synthesized using a one-step green method employing Arctostaphylos pungens Kunth fruit extract at room temperature. The antibacterial properties of both nanostructures were evaluated against Gram-positive Escherichia coli and Gram-negative Staphylococcus aureus bacteria. Scanning electron microscopy (SEM), X-ray diffraction (XRD), ultraviolet–visible spectroscopy (UV–Vis), and infrared spectroscopy (IR) characterized the synthesized products. The morphological changes of the nanostructures come from the variation in the concentration of the precursor salt, silver nitrate (AgNO3). A growth mechanism is proposed that includes the formation of nanospheres and their subsequent transformation into Ag dendrites. Both nanostructures show good antibacterial activity against the tested microorganisms. The Ag dendritic nanostructures presented inhibition zones of 11 mm and 10.7 mm against Escherichia coli and Staphylococcus aureus bacteria. However, the flower-like structure was slightly less effective, presenting 11 and 9.5 mm inhibition zones against the same microorganisms, respectively. [ABSTRACT FROM AUTHOR]

In recent era bacteria that were previously susceptible to different antibiotics are getting tolerant to these drugs. Novel nanoantibiotics can evade these emerging bacterial resistances. Thus, cefadroxil was conjugated to silver and gold nanoparticles (NPs) and resultant nanoconjugates (i.e., Cefd-AgNPs and Cefd-AuNPs) were examined against staphylococcus aureus ATCC 11632. Devised nanoconjugates were characterized by applying diverse range of characterization tools, including UV–visible, IR spectroscopy, scanning electron microscopy and atomic force microscopy (AFM). Moreover, bactericidal potential of Cefd-AgNPs and Cefd-AuNPs was compared with the efficacy of non-conjugated cefadroxil served as control. Experimentally obtained results show that conjugation of cefadroxil with gold and silver NPs enhanced the antibacterial potential of cefadroxil up to 3 and 2 times, respectively. Surface topography of the controlled and treated bacterial cells was also scanned by AFM. Moreover, AFM revealed that effective treatment time of cefadroxil (i.e., 8 h) also get reduced to one half upon conjugation of cefadroxil with both gold and silver (i.e., 4 h). [ABSTRACT FROM AUTHOR]

Nanoparticle biosynthesis mediated by plants, microbes, fungus or algae is a safe and eco-friendly approach addressing various applications in the medicine, cosmetics, biosensors and agricultural industry. Morphology of the synthesized particles depends largely on the type of organism involved, culture-conditions like temperature, pH and the substrate-concentration. This paper reports the synthesis of copper, silver and iron NPs by exposing living cells of D strain of Microbacterium marinilacus and III strain of Stenotrophomonas maltophilia to aqueous solutions of Cu, Ag and Fe ions. These strains were isolated from Damodar-river sediments in Burnpur, Asansol, India and identified by 16S rDNA-sequencing and phylogenetic-tree analysis. NCBI GenBank Accession No. was KT346339 for III and KT346340 for D isolates respectively. UV-spectrophotometer-analysis of culture supernatant and scanning electron microscopy confirmed biogenesis of the nanoclusters. X-ray diffraction and Fourier transformed infrared spectroscopy further confirmed the nano-dimension of the particles. Atomic force microscopy revealed the conformation of nanoparticles. Antibacterial properties of the synthesized particles against gram positive Bacillus cereus and gram negative Escherichia coli were studied through agar-plate-well-diffusion. Effects of the particles on growth of S. maltophilia PM102 were monitored. Data-analysis with one-way-ANOVA and Tukey's-HSD-test was done. Protein-profile of the isolates in the presence and absence of nanoparticles was studied through SDS-PAGE. [ABSTRACT FROM AUTHOR]

The green synthesis of silver nanoparticles (AgNPs) has been proposed as a simple, eco-friendly and cost effective alternative to chemical and physical methods. The Rhus chinensis plant is one of the well studied medicinal plant and its galls find excellent clinical and therapeutic applications. The present study reports the use of water extract from galls of R. chinensis as a reducing agent and formation of AgNPs from silver nitrate solution by a green synthesis route. The AgNPs formation was observed visually by color change and the absorbance peak at 450 nm was observed by UV-Visible spectrophotometer. The shape, size, and morphology of synthesized AgNPs were monitored by transmission electron microscopy and field-emission scanning electron microscopy. The face centered cubic structure of AgNPs was confirmed by X-ray diffraction pattern and element composition by energy dispersive X-ray analysis. The Fourier transform infrared spectroscopy spectrum revealed that the presence of components acts as a reducing and capping agent. The antibacterial activity was performed using the agar well diffusion method. Minimum inhibitory concentration and minimum bactericidal concentration were determined by broth dilution and spread plate method respectively. Synthesized nanoparticles were spotted as triangular and hexagonal shape and the particle size was around 150 nm. [ABSTRACT FROM AUTHOR]