The utility of controlled and sustained release of drugs from polymeric systems, both bulk (hydrogels) and colloids (nanoparticles), is a key point that should be addressed. Unfortunately, classic delivery systems are essentially driven by diffusion, which is very quick due to the high concentration gradient present in the body. Area covered: This review provides an overview of functionalization strategies which have been used to reduce release rates by taking advantage of post-polymerization functionalization of polymers. This paradigm is extremely useful in the pharmacological treatment of several diseases, particularly multifactorial diseases, which may require a variety of release kinetics for different drugs from a single device. Expert opinion: Polymer chains can be functionalized with several post-polymerization strategies in order to link, with a cleavable bond, drug molecules to reactive points of the polymeric network. Following this strategy, the main mechanism related to drug release is the breakage of the link that could be opportunely chosen depending on the medical needs: the weaker the bond, the higher the release rate.
Keywords: Diffusion; hydrogels; nanoparticles; post-polymerization; transport phenomena.