Three types of poly(N-vinylcaprolactam)-based temperature-sensitive microgel particles were synthesized by emulsion polymerization. The uptake of a model drug (calcein) into the particles was analyzed in terms of the amount of calcein absorbed and equilibrium-swelling degree. By incubating the microgels with primary neuronal cell cultures of embrionary rats, cell viability and biocompatibility tests were carried out. The results show that the driving force for the model drug to penetrate into the microgel particles is H-bonding associations. On the other hand, cell death was microgel concentration and incubation period dependent. Microgels can be stored in a dried state and resuspended in water when necessary without changing their swelling-deswelling ability. (C) 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1173-1181, 2010