Eco-friendly synthesis of ZnO nanoparticles using Morinda tinctoria: Applications in environmental health and disease prevention

Zinc plays an important role in skin care, especially in today's polluted environment. In this study, zinc oxide nanoparticles (ZnO NPs) were synthesized using a green method utilizing Morinda tinctoria (MT) leaf extract, known to be rich in polysaccharides. The MT-ZnO NPs were characterized by FTIR, UV-Vis, XRD, FE-SEM-EDX, and zeta potential measurements, confirming their spherical shape, crystallinity, average particle size of approximately 100 nm, and stability. The MT-ZnO NPs exhibited potent antibacterial activity against Pseudomonas aeruginosa and Escherichia coli, and antifungal activity against Aspergillus niger. Antioxidant activity was significant, reaching a 45.32% DPPH scavenging rate at 100 µg/mL, which is close to that of ascorbic acid (53.99%). In in vitro cytotoxicity testing, strong anti- cancer activity (74.3%) against A-375 melanoma cells, which is higher than that in normal NHEK cells (42.3%), and is thought to be due to ROS-mediated apoptosis. MT-ZnO nanoparticles prepared in a gel formulation showed 90% mosquito repellent effect for 60 min, gradually decreasing to approximately 65% after 6 h without adverse effects on the skin. These findings suggest that MT-ZnO nanoparticles are a promising and environmentally friendly agent for skincare, antimicrobial therapy, and prevention of mosquito-borne diseases.