Nanogels: Emerging Smart Platforms for Drug Delivery

Nanogels are nanoscale hydrogel-based drug delivery systems that have gained remarkable attention in recent years due to their unique physicochemical properties and clinical potential. Characterized by high water content, tunable swelling behavior, biocompatibility, and capacity for surface modification, nanogels provide an efficient platform for controlled and site-specific delivery of a wide range of therapeutic agents. Their ability to encapsulate small molecules, proteins, peptides, nucleic acids, and vaccines, while protecting them from enzymatic degradation, makes them superior to many conventional nanocarriers. Importantly, nanogels exhibit stimuli-responsive behavior, releasing drugs in response to environmental cues such as pH, temperature, redox potential, or enzymatic activity, thereby enabling precision medicine. Significant progress has been made in the application of nanogels for cancer therapy, gene delivery, diabetes management, ophthalmic formulations, and brain-targeted treatments. Furthermore, the integration of nanogels with diagnostic agents has opened avenues for theragnostic applications. Despite their immense promise, challenges related to large-scale production, reproducibility, long-term safety, and regulatory approval remain obstacles to clinical translation. This review provides a comprehensive overview of nanogel systems, highlighting their preparation strategies, classification, drug loading and release mechanisms, therapeutic applications, safety considerations, and future directions.