Self-setting particle-stabilized emulsion for hard-tissue engineering

Abstract

Injectable self-setting materials have recently attracted interest for use in minimally invasive medical treatments and tissue engineering. In particular, calcium phosphate cements (CPCs) offer certain specific advantages for the treatment of bone defects. Although the inner structures of set CPCs are important for the apposition and remodeling of new bone, there are still limitations to the design of cements with a well-controlled inner structure.In the present study, we explored self-setting CPCs that generate interconnected macroporous matrices using solid-particle-stabilized emulsion templates. α-Tricalcium phosphate (α-TCP) and poly(ethylene phosphate) sodium salt-coated poly(d,l-lactide-co-glycolide) (PLGA) microparticles were mixed with castor oil and water to form an oil-in-water (o/w) emulsion. The α-TCP and PLGA microparticles functioned as an effective particulate emulsifier by adsorption at the oil–water interface. The resulting emulsion spontaneously set in a humidified atmosphere at ambient temperature. The setting behaviors of different emulsions were characterized through X-ray diffraction analysis and compressive-strength measurements. The PLGA microparticles did not hinder the rate of hardening of the emulsions, and they improved the compressive strengths of the set cements. The PLGA particles incorporated within the set cements were hydrolytically degraded, and the degradation of the PLGA particles resulted in the formation of an interconnected pore structure in the set cement. Finally, mouse osteoblastic (MC3T3-E1) cells were cultivated on the set CPCs. The adherent MC3T3-E1 cells adopted a spindle shape, and significant cellular invasion into the set CPCs was observed after degradation of the PLGA microparticles. In conclusion, self-setting emulsions stabilized with α-TCP and PLGA microparticles constitute a novel candidate material for bone regeneration.