Biosynthesis, characterization and monitoring in vitro antibacterial efficiencies of AgNPs with filamentous cyanobacteria Spirulina sp. And S. Subsalsa against pathogenic bacteria

Abstract

Silver nanoparticles are a fascinating nanomaterial group among metallic nanoparticles for several possible uses, mainly for controlling multidrug-resistant human pathogenic bacteria. The objectives here are to focus on the characterization and observation of antibacterial efficacies of AgNPs biosynthesized using the aqueous extracts of two filamentous non-nitrogen fixing cyanobacteria, Spirulina sp. and Spirulina subsalsa against bacteria. Characterizations of biosynthesized AgNPs with ultraviolet–visible spectroscopy, field emission scanning electron microscopy, Fourier transform infrared spectroscopy, dynamic light scattering, and X-ray diffraction analysis were done. The ultraviolet–visible spectrum demonstrated the reduction of S. subsalsa-AgNPs with a plasmon resonance peak of 458 nm and Spirulina sp.-AgNPs with a peak value of 432 nm, indicative of the yield of biosynthesized AgNPs. The antibacterial efficiencies were observed against MDR strains isolated from clinical samples of this hospital with Gram-negative bacteria, Escherichia coli (MTCC443), Acinetobacter baumannii (MTCC1425), and Gram-positive bacterium, Streptococcus pyogenes (MTCC1982) by the agar-well diffusion method. The minimum inhibitory concentration was 50–100 µg/ml, and the minimum bactericidal concentration value was 80–140 µg/ml in both Spirulina species. The synthesized AgNPs were more potent during in vitro control of MDR h-pathogenic bacteria with the zones of inhibitions at 14 and 15 mm for Spirulina sp.-AgNPs. and 15, 14, and 13 mm for S. subsalsa-AgNPs. Additionally, FESEM images were used to analyze spherical surface morphology with sizes ranging from 40 to 50 µm. The novelty of the study highlights the biosynthesis of AgNPs individually with S. subsalsa and Spirulina sp.; eventually, each cyanobacterial biomass holds some great promise for antimicrobial use against h-pathogenic MDR bacteria. Furthermore, research signifies the AgNP biosynthesis with cyanobacteria, evaluates the biocompatibility, and check for host-toxicities of the biosynthesized AgNPs for future possible therapeutic applications.

Keywords

• Cyanobacteria
• Biosynthesis
• Silver nanoparticle
• Characterization
• Antibacterial efficiency