Biosynthesis, characterization, and antimicrobial assessment of cyanobacterium <i>Spirulina</i> sp. mediated gold nanoparticles, with <i>in silico</i> validation against eubacteria and fungi

This study used gold nanoparticles biosynthesised with the cyanobacterium Spirulina sp. Physical, chemical and optical characteristics of Ssp-AuNPs were examined with a UV-Vis spectrophotometry, dynamic light scattering, Fourier transform infrared spectroscopy, field emission scanning electron microscopy and X- ray diffraction analysis with determination of Zeta potential. Furthermore, the antibacterial and antifungal properties of biosynthesised AuNPs significantly inhibited two Gram-negative pathogenic bacteria, Escherichia coli and Acinetobacter baumannii, and two Gram-positive pathogenic strains, Streptococcus pyogenes and Staphylococcus aureus, as well as the human fungi Candida tropicalis and Trichophyton rubrum in vitro. In addition, molecular docking analysis of 34 ligands using AutoDock identified potential binding interactions with bacterial proteins of E. coli and S. aureus. Compounds such as N-(1-butylpentylidene)-3-ethyl-2,6,10-trimethylundecane, 2,4-di-tert-butylphenol, dibutylphthalate and 2-dimethyl-3(2H)-furanone exhibited favourable binding affinities. Pharmacokinetic profiling further indicated acceptable drug likeness, bioavailability, and safety, with most ligands showing favourable absorption and metabolism and low toxicity risks. Overall, this study uniquely integrates GC-MS-based phycochemical profiling with the dual potential of Ssp-AuNPs as antimicrobial agents; molecular docking and 100 ns molecular dynamics simulations provide molecular-level insights into the bioactive compounds of Spirulina sp. and identify promising drug candidates with strong interaction stability and favourable.