Universal Strategy for Designing Shape Memory Hydrogels

Smart polymeric biomaterials have been the focus of many recent biomedical studies, especially those with adaptability to defects and potential to be implanted in the human body. Herein we report a versatile and straightforward method to convert non-thermoresponsive hydrogels into thermoresponsive systems with shape memory ability. As a proof of concept, a thermoresponsive polyurethane mesh was embedded within a methacrylated chitosan (CHTMA), gelatin (GELMA), laminarin (LAMMA) or hyaluronic acid (HAMA) hydrogel network, which afforded hydrogel composites with shape memory ability. With this system, we achieved good to excellent shape fixity ratios (50-90%) and excellent shape recovery ratios (∼100%, almost instantaneously) at body temperature (37 °C). Cytocompatibility tests demonstrated good viability either with cells on top or encapsulated during all shape memory processes. This straightforward approach opens a broad range of possibilities to convey shape memory properties to virtually any synthetic or natural-based hydrogel for several biological and nonbiological applications.