Biosynthesis of nanostructured silver by green algae and evaluation of its microbicidal property against pathogenic microbes

Present study highlights the in vitro facile approach of silver nanoparticles (AgNPs) synthesis using cell free extract of two green algae Chlorococcum humicola and Chlorella vulgaris, which offers an ecofriendly, economical and sustainable way of biosynthesis of nanoparticle. The colour change from light green to darkest brown within 24 h, and the surface plasma resonance (SPR) peak at 435 and 437 nm for C. vulgaris and C. humicola, respectively, confirms the creation of AgNPs. Transmission electron spectroscopy (TEM) pictures depicted that the average particle size of C. vulgaris and C. humicola synthesized AgNPs were 12.83 and 10.69 nm, respectively. The AgNPs were well scattered, highly stable, and spherical with a tendency of agglomerations. The energy dispersive X-ray (EDX) analysis of particles confirmed the purity and polydispersed character of AgNPs. The biomolecules involved in silver reduction were identified by using Fourier transform infrared spectroscopy (FTIR), which illustrated that proteins and peptides act as capping agents for the formation of AgNPs. Furthermore, the biosynthesized AgNPs exhibited high microbicidal activity against disease causing bacteria viz. Escherichia coli MTCC1687, Salmonella typhi MTCC3231, Klebsiella pneumoniae MTCC4032 and fungus viz. Fusarium solani MTCC6773, Fusarium moniliforme MTCC6576, Penicillium sp. MTCC6489. Use of such a microalgal system for the formation of metal nanomaterials provides a simple, cost-effective alternative model over other methods and the biosynthesized nanoparticles can be used for a number of biotechnological applications.