Development of Bioresorbable Calcium-Phosphate Cements Hybridized with Gelatin Particles and their In Vivo Evaluation Using Pig’s Tibia Model

Novel bioresorbable calcium-phosphate cement (CPC) with anti-washout property was developed by adding thermally cross-linked gelatin particles as pore generator into a CPC. The CPC was composed of α-tricalcium phosphate (α-TCP) and surface-modified hydroxyapatite (HAp) with inositol phosphate as a chelating agent (IP6-HAp). The bioresorbable CPC hybridized with gelatin particles was successfully fabricated by mixing the aqueous sodium chondroitin sulfate solution including Na2HPO4 and the pre-mixed powders composed of α-TCP (72 mass%), IP6-HAp (18 mass%), and the gelatin particles (10 mass%). The hybridized CPC paste showed initial setting time (IST) of 5 minutes and exhibited anti-washout property. Compressive strength after setting for 24 h reached to 4.2 MPa. An in vivo preliminary study using pig’s tibia model demonstrated that the hybridized CPC could be easily injected and set promptly without washout. In addition, no fragmentation in the specimens was observed after 8 weeks implantation. Moreover, a histological observation (Villanueva bone stain) revealed that almost 80% of the hybridized CPC specimens were resorbed and that immature bones were formed inside the specimens.