Biofilm-inhibiting ZnO@Eggshell nanocomposites: green synthesis, characterization, and biomedical potential

This study explored the eco-friendly synthesis, characterization, optimization, and biomedical potential of zinc oxide-eggshell (ZnO@ES) nanocomposites using Althaea officinalis flower extract. HPLC analysis identified pink flower extract as the highest in quercetin (88.452 ppm), making it the optimal choice for synthesis. UV-Vis spectroscopy confirmed ZnO nanostructures (384 nm peak), while characterization analyses using different spectroscopic and microscopic techniques validated their successful incorporation within the eggshell matrix. The hemocompatibility of ZnO@ES nanocomposites was assessed through hemolysis tests, which demonstrated low hemolytic activity (<5%), ensuring blood compatibility. Antimicrobial assays against Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, and Candida albicans revealed significant inhibitory effects, particularly with ZnO@ES4. Agar well diffusion tests showed that while eggshell alone lacked antimicrobial activity, ZnO@ES2 formed inhibition zones against P. aeruginosa and E. coli, whereas ZnO@ES4 was effective against P. aeruginosa, E. coli, and S. aureus. Biofilm inhibition tests further demonstrated that ZnO@ES2 and ZnO@ES4 significantly reduced E. coli and P. aeruginosa biofilms, with ZnO@ES4 being more effective. MTT cytotoxicity assays using L929 fibroblast cells confirmed biocompatibility, with ZnO@ES2 enhancing cell proliferation. By repurposing eggshell waste, this study promotes a circular economy approach, transforming an abundant biowaste into value-added biomaterials. The green synthesis method eliminates the need for toxic chemicals, ensuring an environmentally friendly and sustainable clean production process. These findings support the development of antimicrobial and biocompatible nanocomposites with biomedical applications.