The development of microgels/nanogels for drug delivery applications

Microgels/nanogels are crosslinked polymeric particles, which can be considered as hydrogels if they are composed of water soluble/swellable polymer chains. They possess high water content, biocompatibility, and desirable mechanical properties. They offer unique advantages for polymer-based drug delivery systems (DDS): a tunable size from nanometers to micrometers, a large surface area for multivalent bioconjugation, and an interior network for the incorporation of biomolecules. Present and future microgel applications require a high degree of control over properties. They include stability for prolonged circulation in the blood stream, novel functionality for further bioconjugation, controlled particle size with uniform diameter, and biodegradability for sustained release of drugs for a desired period of time and facile removal of empty devices. This review describes the recent developments of microgel/nanogel particles as drug delivery carriers for biological and biomedical applications. Various synthetic strategies for the preparation of microgels/nanogels are detailed, including photolithographic and micromolding methods, continuous microfluidics, modification of biopolymers, and heterogeneous free radical and controlled/living radical polymerizations.