Synthesis and characterization of silver nanoparticles using Anabaena variabilis as a potential antimicrobial agent

Biogenic silver nanoparticles (AgNPs) are of significant interest due to their widespread application. In order to make nontoxic cost-effective AgNPs, several microorganisms have been utilized. In the present study, emphasis was given to Anabaena variabilis-mediated AgNPs synthesis. Optimal conditions for extract preparation were heating of extraction mixture at 100 degrees C for 5 min, while for AgNPs synthesis, optimal conditions were 1:9 v/v (cell extract: AgNO3 (1 mM)), pH 7.4, and 30 degrees C reaction temperatures. The synthesized AgNPs were characterized initially by UV-Vis spectrophotometer and the maximum absorbance peak was obtained at 440 nm. XRD technique confirmed their crystalline nature. SEM with EDX showed 66% elemental silver by weight, which signified the purity of AgNPs. DLS study showed nearly monodispersed nature of AgNPs. TEM observation confirmed the synthesis of 11-15 nm spherical NPs. FTIR analysis of synthesized AgNPs showed the functional moieties responsible for their bioactivity. The biomolecules of AgNPs were confirmed by LCMS/MS. Anabaena variabilis-mediated AgNPs showed good antibacterial and antifungal activity. In combination with standard antibiotic (streptomycin) and antifungal agents (amphotericin B, fluconazole), AgNPs showed significant synergistic effect. The blend of antibacterial and antifungal properties, coupled with their intrinsic "green" and facile synthesis, made these biogenic nanoparticles attractive in nanomedicine.