Green Synthesis of Different Shapes of Silver Nanostructures and Evaluation of Their Antibacterial and Cytotoxic Activity

Abstract

Silver nanoparticles (NPs) have been demonstrated as a promising antibacterial candidate to fight against resistant pathogens. In this study, different shapes of silver nanostructures (i.e., sphere, rod, and cube) were synthesized by green methods. Morphology, size, and crystalline structure of the produced structures were characterized by UV–visible spectroscopy, scanning electron microscopy (SEM), and X-ray diffraction (XRD). For evaluation of antibacterial activity of silver nanostructures with various shapes, measurement of minimum inhibitory concentrations (MICs) was carried out against Gram-positive (Staphylococcus aureus and Bacillus subtilis) and Gram-negative (Pseudomonas aeruginosa and Escherichia coli) bacteria. The results showed that the concentration of silver nanostructures that prevents bacteria growth is different for each shape, the cubic and rod shape (with sharp edge and vertex) in lower concentrations being more effective than spherical nanoparticles. MTT assay to assess the toxicity of silver nanoparticles showed a concentration and shape-dependent decrease in cell viability in cancer human cells (MCF-7), signifying shape- and dose-dependent toxicity. In addition, the interaction of different nanostructures with serum albumin was evaluated. According to these results, AgNPs with sharper geometry resulted in protein degradation and higher toxicity as compared with smooth or spherical geometries. The results showed that the geometry of silver nanostructures can have quite a significant role in the definition of biological and antibacterial efficacy of NPs, which has significant implications in the design of NPs for various antibacterial applications and will require more consideration in the future.