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.

Polymer microgels offer large opportunities for delivery of biomacromolecular drugs, responding to a range of stimuli, including temperature, ionic strength, and pH, but also external fields and presence of specific metabolites, the latter exemplified below by competition between dextran and free glucose for cross-linking concanavalin A as a glucose-sensitive insulin trigger.Figure optionsDownload high-quality image (110 K)Download as PowerPoint slideResearch highlights
• Microgels provide responsiveness to a range of parameter, which may be used to trigger drug release and in many other aspects of drug delivery.
• Through absence of hydrophobic domains, they provide stability and retained biological activity to protein, peptide, and other biomacromolecular drugs.
• Precluding factors for this include shell formation in the presence of the biomacromolecular drug, and incomplete drug release.
• Model studies point to ways to avoid such problems, e.g., by reducing charge contrast, hydrophobic interactions, and self-assembly.