Calcium phosphate-based resorbable ceramics:: Influence of MgO, ZnO, and SiO2 dopants

Resorbable calcium phosphate (CaP)-based biomaterials are important because they can significantly improve health care by shortening the time necessary for restoration of functional loading of grafted bones. Although synthetic CaPs show exceptional similarities to natural bone, however, they are deficient in one major area, in that they do not have the same mineral content of bone. The focus of our work is to understand the influence of dopants on the physical, mechanical, and biological properties of tricalcium phosphate (TCP) resorbable ceramics with special emphasis toward in vitro strength degradation and cell-materials interactions as a function of time. For this purpose, beta-TCP was doped with magnesia (MgO), zinc oxide (ZnO), and silica (SiO2). Those dopants were added as individual dopants, and their binary and ternary compositions. It was found that these dopants significantly influenced densification behavior and as sintered microstructures of TCP. In vitro mineralization studies in simulated body fluids (SBF) for 12 weeks showed apatite growth on the highly porous compositions either on the surface or inside. From scanning electron microscopic analysis it was evident that surface degradation occurred on all compositions in SBF. Compression strengths for samples up to 12 weeks in SBF showed that it is possible to tailor strength loss behavior through compositional modifications. The highest compression strength was found for binary MgO-ZnO doped TCP. Overall, samples showed either a similar strength level during the 12 weeks test period, or a continuous decrease or a continuous increase in strength depending on dopant chemistry or amount. In vitro human osteoblast cell culture was used to determine influence of dopants on cell-materials interactions. All samples were non-toxic and biocompatible. Dopant chemistry also influenced adhesion, proliferation, and differentiation of osteoblastic precursor cell line 1 (OPC1) cells on these matrices.