Engineering thermoresponsive polymeric nanoshells.

This study describes a family of hollow nanoscale constructs able to display a large and reversible change in size, within a narrow temperature interval. These thermoresponsive nanostructures are generated by crosslinking functionalized amphiphilic molecules, such as poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) triblocks, while constrained to their particular micellar configuration. This contribution focuses on the generation of these supramolecular architectures, by intra-micellarly crosslinking PEO-PPO-PEO dimethacrylate amphiphiles, and investigates their temperature-dependent dimensional behavior. Spherical nanoshells displaying a 200 nm diameter at 15 degrees C, shrink sharply around 28 degrees C, generating a compact structure of approximately 40 nm at body temperature. Thermoresponsive nanotubes were created by generating them from rod-like micelles at higher temperatures. By varying the composition of the triblock, the transition temperature can be fine tuned, from around 25 degrees C to slightly above body temperature. Also, the nanoshells were rendered biodegradable by incorporating aliphatic oligoesters into their structure. Numerous applications for these nanostructures are foreseen in various biomedical areas, such as in drug and gene delivery, in the tissue engineering and in the biosensors field.