In vitro behavior of tape-cast biphasic calcium phosphate ceramics

Objectives: The aim of this study was to investigate the in vitro behavior of biphasic calcium phosphate (BCP) ceramics, consisting of hydroxyapatite (HAP) and b-tricalcium phosphate (TCP), prepared by tape-casting technique for bone-tissue engineering. Methods: The slurries of BCP ceramics were prepared to HAP/b-TCP weight ratios of 100/0 (H100), 75/25 (H75T25), 50/50 (H50T50), 25/75 (H25T75) and 0/100 (T100). The green BCP ceramic sheets were fabricated by tape-casting technique, and were sintered at 1200șC for 4 hours. The sintered BCP ceramics were characterized by X-ray diffraction (XRD). The solubility of BCP ceramics in phosphate buffered saline (PBS) solution with pH 7.4 was monitored during 30 days at 37șC. Cell culture tests were carried out using MC3T3-E1 osteoblast-like cells; the number adherent cells onto BCP ceramics were counted after cell cultivation for 7 days. Results: We confirmed from the XRD pattern that b-TCP in BCP ceramics was transformed to a-TCP at 1200șC, but HAP showed no change. After 30-days' immersion of BCP ceramics in PBS solution, the solubility of BCP ceramics increased with increasing HAP ratio. The BCP ceramics of H100, H75T25, H50T50, H25T75, and T100 had cell numbers of 11.2±1.29, 12.6±0.40, 13.0±1.19, 16.4±2.91, and 14.3±2.66 x10⁴, respectively, showing there to be a tendency for osteoblast-like cell numbers to increase with increasing TCP ratio. Meanwhile, H100 showed a significantly lower cell number than H25T75 (Scheffe's test, p<0.05). Thus, it was assumed that the higher solubility of H100 interrupted cell proliferation onto the BCP ceramics. Conclusion: The results of this investigation indicated that the in vitro behavior of tape-cast BCP ceramics strongly depended upon the weight ratio of HAP/TCP. Furthermore, the solubility of BCP ceramic surface was considered to have affected cell proliferation. (Supported by a Grant-in-Aid for Young Scientists (B)(No.19791463) from the Japan Society for the Promotion of Science)