Enhancing the Cell-Biological Performances of Hydroxyapatite Bioceramic by Constructing Silicate-Containing Grain Boundary Phases via Sol Infiltration

Hydroxyapatite (HA) is well-known as one of the excellent bone repair biomaterials because of its chemical similarity with biological apatite. However, weak bioactivity obstructs its application. Although the bioactivity of HA bioceramic could be enhanced by the incorporation of bioactive glass (BG), the dramatic decrease of its mechanical property is consistently a disturbance to the reliable efficacy of traditional modified HA bioceramic. In this study, HA bioceramic was modified by infiltration of BG sol and formation of silicate-containing grain boundary phases during subsequent sintering. The phase compositions, microstructure, mechanical performance, in vitro degradation behaviors, and osteogenesis of the bioceramic were investigated. The modified HA bioceramic exhibited an interesting phenomenon in which the HA grains were uniformly enveloped by the small silicate-containing grains in the boundaries of HA grains. The microporosity of modified HA bioceramics was up to 25.27% ± 0.01%, much higher than that of unmodified HA bioceramic (1.74% ± 0.27%). The compressive strength of the modified HA bioceramic via BG sol infiltration was much higher than that of the HA bioceramic modified by BG via mechanical blending method, though slightly lower than that of the blank. Moreover, mouse bone mesenchymal stem cells (mBMSCs) cultured on modified bioceramic displayed better adhesion morphology and proliferation, and had an enhanced expression of osteogenesis-related genes. This study offers a new strategy to improve the bioactivity of HA bioceramic without obvious deterioration in mechanical strength.