Improved Biological Properties of Calcium Phosphate Cement by Nacre Incorporation: An In Vitro Study

To investigate the effect of incorporating nacre into calcium phosphate cement (CPC), one of the most commonly used bone substitutes. In this study, nacre at 25 wt% and 50 wt% was incorporated into a CPC powder mixture. The composites were characterized, and their in vitro osteoblast functions were examined. X-ray diffraction (XRD) patterns revealed that the inorganic composition of the composites mainly was consisted of aragonite, hydroxyapatite ( HA) and carbonate-apatite. Scanning electron microscopy (SEM) and micro-computed tomography (micro-CT) images indicated that the porosity of the CPC composites was increased by nacre incorporation. However, the setting time increased, and the compressive strength decreased with increased nacre addition into CPC. In addition, the in vitro degradation rate of the nacre/CPC composites was faster than that of CPC. Cell tests revealed that nacre/CPC composites are cytocompatible and, compared with CPC, could enhance the cell adhesion, spreading and proliferation of MC3T3-E1 cells on materials. Moreover, the composites exhibited stronger osteogenicity than CPC and inorganic calcium carbonate-incorporated CPC composites by promoting alkaline phosphatase ( ALP) activity and the gene expression levels of ALP, runt-related transcription factor 2 (Runx2), osteocalcin (OCN) and osteopontin (OPN). Thus, nacre could be a promising additive to increase the biological performance of CPC.