Antimicrobial and Antifungal Activities of Bletia Purpurea-Mediated Gold Nanoparticles

The development of antimicrobial resistance and the requirement for new antifungal agents have led to the investigation of alternative approaches for the treatment of microbial infections. In this research, we describe the synthesis, characterization, and assessment of antimicrobial and antifungal properties of gold nanoparticles (AuNPs) mediated by Bletia purpurea. The orchid extract was used as a reducing and capping agent. The AuNPs were characterized by UV-Vis spectroscopy, transmission electron microscopy (TEM), energy-dispersive spectroscopy (EDS), and X-ray diffraction (XRD). The AuNPs were found to be spherical in shape with an average size of 20 nm and a surface plasmon resonance peak of 530 nm. The antimicrobial potential of AuNPs was assessed against a number of bacterial strains, namely Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, and Klebsiella pneumoniae, by the broth microdilution technique. The AuNPs were found to possess strong antimicrobial potential with minimum inhibitory concentrations ranging from 0.1 to 1.5 μg/mL. The antifungal properties of AuNPs were tested against various fungal strains such as Candida albicans, Aspergillus niger, and Fusarium oxysporum using the broth microdilution technique. The AuNPs showed strong antifungal properties with MIC values ranging from 0.05 to 1.0 μg/mL. Mechanistic studies showed that AuNPs caused membrane damage, oxidative stress, and DNA fragmentation in microbial cells, resulting in cell death. The AuNPs also showed synergistic properties with existing antibiotics, increasing their potency against resistant microorganisms. The efficacy of Bletia purpurea-mediated AuNPs has been shown in this study to have potential as a novel antimicrobial and antifungal agent, providing a promising approach to counteract microbial infections and the rising problem of antimicrobial resistance.