Antioxidant and antimicrobial activities of Spirulina platensis extracts and biogenic selenium nanoparticles against selected pathogenic bacteria and fungi

Abstract

This study investigated the antimicrobial and antioxidant activity of three <i>Spirulina</i> extracts (methanol, acetone, and hexane) and the biological selenium nanoparticles (SeNPs) fabricated by <i>Bacillus subtilis</i> AL43. The results showed that <i>Spirulina</i> extracts exhibited antimicrobial activity against tested pathogens. Besides, <i>Spirulina</i> extracts significantly scavenged ABTS and DPPH radicals in a dose-dependent manner. The methanolic extract had higher total phenolic content, antimicrobial activity, and antioxidant activity than other extracts. The selenium nanoparticles were synthesized by <i>Bacillus subtilis</i> AL43 under aerobic conditions and were characterized as spherical, crystalline with a size of 65.23 nm and a net negative charge of -22.7. We evidenced that SeNPs possess considerable antimicrobial activity against three gram-positive, three gram-negative bacteria, and three strains from both <i>Candida</i> sp. and <i>Aspergillus</i> sp. Moreover, SeNPs were able to scavenge ABTS and DPPH radicals in a dose-dependent manner. An association was found between the total phenolic content of <i>Spirulina</i> and SeNPs and their biological activities. Our results indicate that <i>Spirulina</i> and SeNPs with significant antimicrobial and antioxidant activities seem to be successful candidates for safe and reliable medical applications.