Eco-Friendly Metal Complex Nanozymes Emerging Tools in Diagnostics and Therapeutics

Eco-friendly metal complex nanozymes represent a rapidly evolving class of catalytic nanomaterials engineered to mimic natural enzymes while adhering to green chemistry principles. Traditional nanozyme synthesis relies on hazardous reductants, toxic solvents, and energy-intensive conditions, resulting in materials with limited biocompatibility and notable environmental burdens. Green synthetic approaches—including plant-mediated phytochemical reduction, microbial templating, bio macromolecular scaffolding, mechanochemical processing, and aqueous low-temperature fabrication—yield metal complex nanozymes with enhanced safety, improved catalytic efficiency, and reduced ecological impact. These nanozymes exhibit versatile catalytic behaviours, such as peroxidase-, oxidase-, catalase-, superoxide dismutase-, and Fenton-like activity that support advanced diagnostic and therapeutic applications. Expanded diagnostic uses include colorimetric biosensors, electrochemical platforms, fluorescence-based sensing, wearable devices, and imaging-guided systems. Therapeutic applications range from antioxidant and antimicrobial treatments to cancer chemodynamic therapy, immunomodulation, wound healing, and metabolic disease intervention. Despite significant promise, challenges remain regarding toxicity, biodegradation, environmental persistence, and clinical translation. This extended review provides an in-depth examination of eco-friendly synthesis strategies, catalytic mechanisms, biomedical applications, and future research directions, including machine-learning-driven design, bioinspired catalysis, and circular chemistry frameworks.