Thermoresponsive behavior and rheology of SiO 2 –hyaluronic acid/poly( N ‐isopropylacrylamide) ( NaHA / PNIPAm ) core–shell structured microparticles

BACKGROUND Injectable 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. RESULTS Microparticles composed of a hard SiO 2 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 Ca 2+ ions. CONCLUSION The introduction of NaHA and SiO 2 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. © 2014 Society of Chemical Industry