Osteoblast activity on carbonated hydroxyapatite

Hydroxyapatite (HA), has been used commonly as a bone substitute and as a scaffold in bone tissue engineering. However it has certain drawbacks such as limited biodegradability and osteointegration properties. Other forms of HA, for example, carbonated hydroxyapatite (CHA) could prove to have enhanced bioactivity as they more closely mimic the chemical composition of the apatite found in human bone. The aim of this study was to test the efficacy of CHA in comparison to HA used as a control. The CHA (4.9 wt %) and the HA discs were seeded with MC3T3-E1 osteoblastic cells. Results revealed a trend of increased cell attachment on the HA discs at day 0, however, the cell proliferation on the CHA discs at 7 and 28 days showed no significant difference in comparison to the HA control. SEM of the CHA discs showed surface irregularities at 7 days indicating dissolution. Also at 7 days, SEM demonstrated cell attachment and extracellular matrix production on both the CHA and HA samples. There was no significant difference in the total amount of collagen produced in the CHA samples relative to the HA control samples at 28 days as evaluated by the hydroxyproline assay. Real time PCR revealed mRNA increase by 2.08, 7.62, and 9.86 fold for collagen I a1, collagen III a1, and osteocalcin respectively on the CHA as compared to the HA discs. This study demonstrates the use of CHA as a biocompatible material that has potentially increased biodegradation properties and osteogenic capability in comparison to HA.