Surface-engineered microparticles; with a biodegradable polymer core and a programmable thermoresponsive biocompatible copolymer corona are produced. The particles form free-flowing dispersions below 37 degrees C, but form porous space-filling gels above this temperature, as a result of chain collapse of the copolymer corona. When particles are mixed with biological materials, they form encapsulating gels that can support cell growth.