Surface engineering of nanocarriers with polymer coatings: materials, strategies, functional outcomes, and clinical...

Polymer coating of nanocarriers has emerged as a powerful strategy to improve the performance of advanced drug delivery systems by enhancing stability, bioavailability, targeting capability, and therapeutic efficiency. Surface functionalization with biocompatible polymers can significantly modify the physicochemical and biological behavior of nanoparticles, enabling improved interaction with biological barriers and controlled drug release profiles. This review provides a comprehensive overview of the most widely used polymers for nanocarrier surface modification, including chitosan, alginate, hyaluronic acid, polyethylene glycol (PEG), methacrylate copolymers, pectin, dextran, and poly-L-lysine. The mechanisms by which these polymers enhance nanocarrier functionality are discussed in detail. In addition, the review summarizes commonly employed coating techniques such as adsorption, covalent conjugation, layer-by-layer assembly, and polymer grafting, highlighting their influence on nanoparticle characteristics and therapeutic performance. Particular emphasis is placed on the pharmaceutical outcomes associated with polymer-coated nanocarriers, including improved drug stability, enhanced bioavailability, site-specific targeting, and prolonged circulation time. Finally, the major scientific, manufacturing, safety, and regulatory challenges that limit the clinical translation of polymer-coated nanocarrier systems are critically discussed. Overall, polymer surface engineering represents a promising approach for the development of next-generation nanomedicines, although further advances in large-scale manufacturing, standardized characterization, and regulatory frameworks are required to facilitate their successful clinical and commercial implementation.