Green Synthesis of ZnO Nanoparticles From <i>Spirulina platensis</i> : Antimicrobial and Cytotoxic Evaluation With Molecular Docking Studies

Zinc oxide nanoparticles (ZnO NPs) have drawn some attention due to its antimicrobial properties and potential for their usage in biomedicine. ZnO NPs were synthesized using algal biomass filtrate, characterized subsequently, and the antimicrobial, antibiofilm, and cytotoxic activities of the ZnO NPs were evaluated. The synthesized ZnO NPs were characterized with fourier transform infrared, X-ray Diffraction, scanning electron microscopic, and transmission electron microscopy to analyze their morphological and compositional properties. Agar well diffusion, time-kill assays and antibiofilm experiments were conducted to assess antibacterial efficacy, while Artemia salina nauplii were used to evaluate cytotoxicity. It was found that ZnO NPs had hexagonal wurtzite crystal structure, uniform nanoscale morphology ranging 20-90 nm, and high phase purity. ZnO NPs exhibited potent antibacterial activity, further confirmed by molecular docking analysis. Strong antibiofilm efficacy, reducing biofilm biomass by up to 95%. Exceptional results were shown by wet lab and docking validation. The PBP2a protein of S. aureus showed a binding score of -7.7, indicating strong inhibition by the ZnO NPs. These nanoparticles exhibit a dose-dependent response, where minimal toxicity was observed at lower concentrations. This study highlights the potential of algae-mediated ZnO NPs as a green, sustainable antimicrobial platform that may mitigate the microbial resistance problem.