From clinic to ecosystem: sustainable zinc oxide nanoparticles as dual-purpose agents for Big Health

green routes, have emerged as multifunctional agents driving the "Big Health" paradigm, which integrates human health, environmental sustainability, and technological innovation. This review systematically examines their multifaceted applications in medical and environmental fields. In healthcare, S-ZnO-NPs exhibit potent antibacterial activity against multidrug-resistant pathogens, enable targeted drug delivery, accelerate wound healing, and facilitate bioimaging. Environmentally, they drive innovations in photocatalytic degradation of organic pollutants, water disinfection, heavy metal remediation, and air purification, while contributing to renewable energy technologies like solar cells and hydrogen production. Critical analysis of risks, including nanotoxicity and ecological accumulation, highlights the need for surface functionalization, refined green synthesis, and hybridization. This review positions S-ZnO-NPs as key tools for achieving Sustainable Development Goals (SDGs) under the Big Health framework, bridging medical and environmental resilience through sustainable nanotechnology.