Overview

Physical hydrogels present direct interactions between polymeric chains and forms non-permanent networks, providing an attractive alternative to chemically cross-linked systems. These hydrogels allow incorporation of macromolecular drug substances under mild process conditions, comprising properties such as water permeability, biocompatibility and tensile strength. The aim of the present work was to provide an overview of physical hydrogels for drug delivery applications. The main focus of this review was based on chemical and structural composition, and on the physicochemical properties necessary for drug release. The structural basis of these drug delivery systems was discussed on the many different macromolecular structures presented: physical entangled networks of linear polymers, polymer blends and composites block or graft copolymers and hydrogels formed by aggregation or complexation of polymers, intended for drug, peptide and protein delivery applications.