Understanding the kinetic arrest in deswelling microgels

Biofriendly microgels, like PNIPAM and dextran, find numerous applications as microscopic delivery agents for advanced therapies of cancer, diabetes, and bacterial infections. We use mesoscale computer simulations to model the deswelling kinetics of spherical microgels. Deswelling occurs as the result of gel-solvent phase separation, leading to the hydrogel network collapse and in certain conditions, to the formation of a dehydrated “skin layer” at the gel-solvent interphase. This dehydrated skin layer hinders solvent flow from the microgel interior which arrests the kinetics of the collapsing microgel. We examine the conditions at which the skin forms and probe how these conditions depend on the microgel size, porosity, and micromechanics. These findings can be useful for designing microgel based drug release systems with controlled release profiles, leading to more effective disease treatments.