Comparative Analysis of ZnO Nanoparticles: Cytotoxic and Genotoxic Effects According to the Synthesis Method

This study presents a comparative evaluation of the cytotoxic and genotoxic effects of zinc oxide nanoparticles (ZnO NPs) synthesized using three different methods: green synthesis (ZnO_Green), green synthesis followed by APTES functionalization (ZnO_Green-APTES), and conventional chemical synthesis (ZnO_Chem.). The nanoparticles were characterized by X-ray diffraction (XRD), UV-Vis spectroscopy, and dynamic light scattering (DLS) with zeta potential analysis, revealing significant differences in crystallinity, optical behavior, and colloidal stability depending on the synthesis method. The biological effects were evaluated using the Allium cepa AgNOR assay and the alkaline comet assay in human lymphocytes at two concentrations (1 and 50 mg/mL). The results demonstrated that all ZnO NPs induced alterations in nucleolar activity and chromosomal integrity, with an increase in the number of AgNORs and the presence of mitotic abnormalities, indicating genotoxic stress. The comet assay revealed a clear increase in dose-dependent DNA damage across all treatments, with ZnO_Chem. exhibiting the greatest genotoxicity, followed by ZnO_Green-APTES and ZnO_Green. Despite maintaining cell viability above 75% under most conditions, variations in viability suggested that surface chemistry and functionalization significantly influence nanoparticle-cell interactions. In this regard, both the synthesis route and surface modification play a fundamental role in modulating the biological impact of ZnO NPs, underscoring the need for controlled design strategies to optimize their safety in biomedical and environmental applications.