Biocompatibility, Bioactivity and Mechanical Properties of Portland Cement and Portland Cement-Metakaolin Blends for Bone Tissue Engineering Applications

Abstract

We studied the potential applications of Portland cement and Portland cementMetakaolin blends as scaffolding materials for load bearing bone tissue engineering. Cementitious pastes were prepared by mixing Portland cement and Metakaolin at different ratios (100:0, 85:15), and hydrated under a concentrated CO 2 atmosphere (carbonated pastes). Pastes fabricated similarly, but hydrated under normal atmospheric conditions were used for comparison (non-carbonated pastes). Compressive tests were run to evaluate the mechanical properties of the pastes. The bioactivity of the samples was tested in a simulated body fluid (SBF) solution for 1 and 4 days. Sample morphology and chemistry were characterized via scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS), respectively. The cytocompatibility was studied using human osteosarcoma (HOS) cell cultures and the direct contact assay. Mechanical characterization did not show significant differences in the compressive strength of the blends compared to pure cement controls. The bioactivity test revealed that the pastes induced surface precipitation of calcium phosphate (CaP) when exposed to the SBF solution (as confirmed by SEM and EDS). Non-carbonated pastes induced early CaP precipitation. Cytocompatibility experiments showed that the carbonated blends allowed adequate cell growth. Non-carbonated blends presented a highly cytotoxic behavior. The introduction of Metakaolin did not affect the cytocompatibility of the samples. These results show that Portland cement and Portland cement-Metakaolin blends could present suitable characteristics for applications as scaffolding materials in load bearing bone tissue engineering.