In vitro bioactivity and cytocompatablity of an injectable calcium phosphate cement/silanated gelatin microsphere composite bone cement

Abstract

Different weight ratios of microemulsion-based gelatin uniform microspheres (GMs) were added to the tetra calcium phosphate (TTCP)-based cement (CPC) to investigate the physical, mechanical and apatite-forming ability of the CPC. The GMs contained 20 wt% of glycidoxypropyltrimethoxysilane (EPPTMS) as a crosslinking agent. The average size of GMs was on the order of 35 μm. For CPC, the initial and final setting times were 10 min and 21 min, respectively. These values were prolonged up to 18 min and 28 min, respectively, for CPC containing 10 wt% of GM (CPC-10GM). The highest injectability percentage and injection time was related to the CPC-10GM. The highest mechanical values were related to CPC-5GM while CPC-10GM possessed the lowest compressive strength and Young's modulus. Apatite formation on the surfaces of all samples was confirmed by acellular in vitro bioactivity experiment after various periods of soaking time in simulated body fluid (SBF). Needle-like HA precipitates were manifested on the surface of CPC-5GM. According to MTT colorimetric assay, the viability rate of cells on the surfaces of CPC-5GM and CPC increases significantly with time. An appropriate attachment of G-292 cells on the surface of both samples after 48 h was observed by DAPI staining and SEM imaging methods. There was considerable difference in the ALP activity per cell basis between CPC and CPC-5GM at intervals of 7–21 days. These results indicate the potential of the CPC–5GM composites to be used in bone replacement.