Zinc Bismuthate-Based Nanocomposites: Promising Antimicro-Bial Properties for Biomedical Applications

Background/Objectives: The growing threat of antimicrobial resistance (AMR) has inten-sified the search for innovative antimicrobial materials. Herein, we synthesized and characterized zinc bismuthate-based nanocomposites (ZB1 and ZB4) and investigated their antimicrobial efficacy against two Gram-positive bacteria (Staphylococcus aureus and Corynebacterium diphtheriae), one Gram-negative bacterium (Klebsiella pneumoniae), and two fungal pathogens (Cryptococcus neoformans and Candida albicans). Toxicity was further as-sessed using Tenebrio molitor larvae as an alternative model. Methods: Nanocomposites were prepared via a hydrothermal process and characterized using X-ray diffraction (XRD), Raman spectroscopy, Zeta potential, and high-resolution transmission electron microscopy (HR-TEM). Antimicrobial activity was evaluated through disk diffusion as-says coupled with minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) assessments. Results: ZB1 and ZB4 inhibited S. aureus (10.7 ± 1.2 mm and 11.3 ± 1.2 mm), C. diphtheriae (10.7 ± 1.1 mm and 11.3 ± 1.1 mm), and C. neoformans (10.7 ± 1.1 mm and 11.7 ± 2.9 mm), while no inhibition was observed for C. albicans and K. pneumoniae. From MIC and MFC evaluations, ZB1 was effective up to 1000 μg/mL, and ZB4 up to 500 μg/mL. Toxicity assays revealed survival rates of 70% for ZB1 and 60% for ZB4, with no statistically significant differences compared to the control (p = 0.156). Notably, ZB4 is a promising candidate due to its enhanced antimicrobial performance and moderate toxicity. Conclusions: Our findings highlight ZB1 and ZB4 nanocomposites as promising antimicrobial agents, offering new avenues in nanotechnology-driven healthcare solutions aimed at tackling antimicrobial resistance.