Eco‐Friendly ZnO Nanoparticle Synthesis and Colostrum Coating: Structural Insights and Biomedical Potential

ABSTRACT The eco‐friendly synthesis of zinc oxide nanoparticles (ZnONPs) using Grewia asiatica stem extract and their subsequent coating with freeze‐dried bovine colostrum powder was explored for biomedical and environmental applications. This study investigated the role of phytochemicals as natural reducing and stabilizing agents in ZnONP synthesis, while also evaluating the structural and functional impact of colostrum coating. Ultraviolet‐visible spectroscopy confirmed ZnONP formation, with a characteristic absorption peak at 372–377 nm, indicative of ZnO bandgap transitions. Fourier‐transform infrared spectroscopy confirmed colostrum coating by showing shifts in Zn–O bond peaks (400–500 cm −1 ) and amide I (1616.2 cm −1 ) and amide II (1547.1 cm −1 ) bands. Scanning electron microscopy revealed granular nanoparticles (78.79–81.20 nm), increasing to 88 nm after coating. Energy‐dispersive X‐ray spectroscopy detected zinc, oxygen, carbon, and calcium, with an additional magnesium peak attributed to colostrum. X‐ray diffraction confirmed the crystalline wurtzite structure with peaks in the 30° to 40° range. Zeta potential analysis indicated improved colloidal stability with colostrum. C–ZnONPs maintained 14‐day stability in fetal bovine serum via protein corona‐mediated steric effects. Antioxidant activity using the 2,2‐diphenyl‐1‐picrylhydrazyl assay showed G. asiatica extract had the lowest half‐maximal inhibitory concentration (IC₅₀) (5.86 ± 0.04 μg/mL), followed by C–ZnONPs (11.72 ± 0.02 μg/mL), outperforming ascorbic acid and uncoated ZnONPs. Antibacterial assays against Staphylococcus aureus , Escherichia coli , Salmonella typhi , and Klebsiella pneumoniae showed C–ZnONPs had the highest inhibition zones (13–22 mm). C–ZnONPs also showed dose‐dependent cytotoxicity against HeLa cells (IC₅₀ ≈ 34.09 μg/mL). These findings validate the successful eco‐friendly synthesis and coating of ZnONPs, highlighting their potential in nanomedicine, catalysis, and targeted drug delivery.