Synthesis and characterization of SiO2–gel microparticles as injectable implant biomaterials

Microparticles with a core–shell structure were synthesized from SiO 2 particles as core and thermally sensitive hyaluronate–poly( N -isopropylacrylamide) (HA–PNIPAM) hydrogel as shell. The SiO 2 –HA–PNIPAM microparticles were injectable at room temperature and assembled to settle on to biosurfaces. Dynamic light-scattering measurements at different temperatures showed that the temperature-dependence of the diameters ( d ) of SiO 2 –HA–PNIPAM microparticles was reversible. d decreased abruptly when the temperature was increased to their lower critical solution temperature of 307 K. The Mw of HA and the extent of modification by glycidyl methacrylate, D m , had clear effects on the sizes of the microparticles and their thermal sensitivity. Fluorescein, selected as model drug, was encapsulated in the gel shell to study the dynamics of drug release by this microparticle at body temperature.