Evaluation of antimicrobial activities of blue-green algae-mediated silver and gold nanoparticles

Recently, green nanotechnology is considered a more suitable and safer tool for medical applications due to its nature reductants with low toxicity and low eco-hazard. The micro-algal biomass was used for the nanoparticles biosynthesis, depending on using whole algal cell cultivation. During the current study, cyanobacteria Oscillatoria sp. and Spirulina platensis exhibited their ability to synthesize silver oxide (Ag 2 O|AgO-NPs) and gold nanoparticles (Au-NPs), respectively. The characterization results confirmed the formation of Oscillatoria sp.-mediated silver oxide nanoparticles ( O .Ag 2 O|AgO-NPs) and S. platensis -mediated gold nanoparticles ( S. Au-NPs). Three different methods had been examined, (i) culture-free cells (secondary metabolites), (ii) algal aqueous extract, and (iii) whole cells cultivation (in vivo). UV–Vis spectroscopy confirmed the biosynthesized O. Ag-NPs at 438 nm, while S. Au-NPs reached 545 nm by whole cells cultivation technique. TEM scanning indicated the formation of spherical-shaped O .Ag 2 O|AgO-NPs with an average size ranged between 10.49 and 45.81 nm. S. Au-NPs also were detected in triangular, pentagonal, and slightly spherical shapes with an average size of 15.49–55.08 nm. Both O. Ag 2 O|AgO-NPs, and S .Au-NPs demonstrated antibacterial and antifungal properties against Gram-positive and Gram-negative bacteria. S .Au-NPs were more effective than O .Ag 2 O|AgO-NPs, which recorded high significant MIC results against Bacillus subtilis ATCC 19659 (1.95 μg/ml), Salmonella typhi ATCC14028 (3.90 μg/ml), and Candida tropicalis ATCC 1380 (1.1 μg/ml) after 24 h treatment, comparing with the control. It is concluded that O .Ag 2 O|AgO-NPs and S. Au-NPs have efficient antibacterial and antifungal activities.