Biogenic Zinc Oxide Nanoparticles Synthesized via Melaleuca quinquenervia Extract for Transdermal Delivery: Anti-Aging, Skin Whitening, and Anti-Inflammatory Performance

This study evaluated the microwave-assisted green synthesis of zinc oxide nanoparticles (ZnO NPs) utilizing Melaleuca quinquenervia leaf extract (MQLE) as a sustainable reducing and capping agent. The synthesized bio-capped ZnO NPs exhibited a pure crystalline structure with an average hydrodynamic size of 82.6 nm. The biological profiles of the nanoparticles were systematically evaluated. Results demonstrated that bio-capped ZnO NPs possessed superior antioxidant, antityrosinase, anti-aging, and anti-inflammatory activities compared to chemically synthesized ZnO NPs (Che-ZnO NPs) and raw MQLE. Specifically, bio-capped ZnO NPs effectively suppressed melanin synthesis in human epidermal melanocytes (HEMn) and down-regulated key inflammatory mediators. Biocompatibility assessments based on ISO 10993-5 criteria revealed that bio-capped ZnO NPs maintained high cell viability at their effective working doses, with safe dosage thresholds (viability > 70%) determined at 175 mg/L for CCD966SK, 225 mg/L for HEMn, and 175 mg/L for Raw264.7 cells. The safe doses significantly exceeded the concentrations required for their physiological functions, whereas Che-ZnO NPs displayed prominent cytotoxicity. In conclusion, MQLE-mediated green synthesis provided a safe, biocompatible, and high-performance platform for ZnO NPs, offering great potential for advanced cosmetic and transdermal biomedical applications.