Biomacromolecules in microgels — Opportunities and challenges for drug delivery

This brief review aims at providing some illustrative examples on the interaction between microgels and biological macromolecules, with special focus on peptides and proteins, as well as current applications of such systems in drug delivery. In doing so, novel insights on factors affecting peptide/protein incorporation to, distribution within, and release from, sparsely cross-linked microgels are addressed, including effects of network charge and cross-linking density, as well as peptide/protein length/size, charge (distribution), and hydrophobicity. Effects of ambient conditions are also illustrated, with special focus on pH and ionic strength. Notably, factors precluding the application of microgel systems in biomacromolecular drug delivery, e.g., shell formation and incomplete drug release, are discussed, together with challenges and opportunities of these effects in the application of biomacromolecule/microgel systems in drug delivery.