A Study of Antimicrobial Activity of Biosynthesized Nanoparticles via Two Different Methods by Freshwater Cyanobacteria Nostoc sp.

Today, the production of green silver nanoparticles by cyanobacteria as antimicrobial agents is widely used in medical and therapeutic industries. In this study, considering that so far no study has been conducted to investigate the potency of cyanobacteria Nostoc sp. as aquatic water belonging to the freshwater of Golestan province, we decided to evaluate the potential of this strain in the biosynthesis of silver nanoparticles by performing different techniques.

After the growth and molecular identification of cyanobacteria Nostoc sp. in the BG-110 culture medium in the growth chamber, two wet biomass and boiling methods were used to produce silver nanoparticles. Then, by inoculating wet biomass at concentrations of 1, 2, and 3 mM silver nitrate and comparing color change, UV-Vis spectroscopy peaks, and measuring stability at 0, 12, 24, and 48 hours, the most efficient method of silver nanoparticle biosynthesis was selected. In addition, instrumental analysis of Raman and Fourier Transform Infrared (FTIR) spectroscopy, Dynamic Light Scattering (DLS), Scanning Electron Microscopy (SEM), and antimicrobial disk antimicrobial properties for the best and most stable nanoparticle production method was done.

Among the two methods used in the production of silver nanoparticles, by examining the dark brown color and the strong 420 nm peak obtained from UV-Vis spectroscopy, the wet biomass method at a concentration of 1 mM at zero time had the highest adsorption compared to the boiling method. The results of FTIR showed successful production of silver nanoparticles using wet biomass of cyanobacterium Nostoc sp. at a concentration of 1 mM silver nitrate at time zero as a safe and biodegradable method, environmentally friendly, low cost, and in accordance with the principles of green chemistry. In addition, the results of FTIR showed that biosynthesized silver nanoparticles had a protein coating that plays a major role in the reduction and stability of silver nanoparticles. The DLS results showed that the nanoparticles produced were between 28 and 50 nanometers in size and the average size of silver nanoparticles was 16.1 nanometers. The results of SEM microscopy showed that the size of the produced nanoparticles was between 28 and 50 nm in terms of spherical morphology. Also, the results of the one-way analysis of variance and Tukey test showed significant inhibitory power of silver nanoparticles against Staphylococcus aureus, E. coli, and Pseudomonas aeruginosa.

Cyanobacteria Nostoc sp. can be used as a potential factor in the production of silver nanoparticles with unique properties and performance for various applications in medicine, industry, etc.