Tunable Dual-Thermoresponsive Core-Shell Nanogels Exhibiting UCST and LCST Behavior.

Thermoresponsive polymers change their physical properties as the temperature is changed and have found extensive use in a number of fields, especially in tissue engineering and in the development of drug delivery systems. The synthesis of a novel core-shell nanogel composed of N-isopropylacrylamide and sulfobetaine by reversible addition fragmentation chain transfer polymerization is reported. The core-shell architecture of the nanogels is confirmed using energy dispersive X-ray spectroscopy in scanning transmission electron microscopy. These nanogels exhibit dual thermoresponsive behavior, i.e., the core of the nanogel exhibits lower critical solution temperature, while the shell displays upper critical solution temperature behavior. Transition temperatures can be easily tuned by changing the molecular weight of the constituent polymer. These nanogels can be efficiently used in temperature-triggered delivery of therapeutic proteins and drugs.