Thermally activated reversible shape switch of polymer particles.

The particles that can reversibly switch shape in response to an environmental stimulus are preferable for controlling the performance of drug carriers. In this work, we present a facile strategy towards the design and fabrication of polymer particles that can reversibly switch their shape on the basis of a biocompatible and biodegradable polymer network containing well-defined six-arm poly(ethylene glycol)-poly(ε-caprolactone) (6A PEG-PCL). These polymer particles have a capacity of reversibly changing shape from spherical to elliptical either extracellularly or intracellularly with the cyclic heating and cooling between 43 °C and 0 °C under a stress-free condition via a reversible two-way shape memory effect (2W-SME) of a polymer matrix. This study of the shape-switching particles opens up exciting possibilities for engineering dynamically shape-switching drug delivery carriers to either avoid or promote phagocytosis.