BACKGROUNDInjectable polymer gels for tissue engineering offer specific advantages over preformed scaffolds. They can transform from a sol to a block gel as a response to an external stimulus. One effective strategy for improving the mechanical strength of a gel is to introduce an inorganic material. RESULTSMicroparticles composed of a hard SiO2 core covered with a thermoresponsive hybrid gel (sodium hyaluronate/poly(N-isopropylacrylamide); NaHA/PNIPAm) were synthesized. The microparticles were characterized by dynamic light-scattering and transmission electron microscopy; rheological measurements were also performed. The microparticles were perfectly spherical and had a core-shell structure. They can perform a sol-gel transformation, that is, they shrank and assembled to form a macroscopic hydrogel through physical cross-linking at the gelation temperature (T-gel), which was determined by rheological measurements. The T-gel was adjusted by changing the concentration of microparticles or Ca2+ ions. CONCLUSIONThe introduction of NaHA and SiO2 improved the mechanical properties of the macroscopic gels. The rigidity and stability of the macroscopic gel were controlled by the molecular weight of NaHA and the amount of PNIPAm. Such injectable hydrogels might have potential as scaffold biomaterials, and are expected to be the ink' for three-dimensional bioprinters. (c) 2014 Society of Chemical Industry