Time-dependent variation of the surface structure of bioceramics in tissue culture medium and the effect on adhesiveness of cells

Biocompatible ceramics made of beta-tricalcium phosphate (TCP) were found to be actively changing their surface characteristics in tissue culture medium. The time-dependent variation of the zeta potential of TCP ceramics immersed in distilled water and in culture medium with and without addition of fetal bovine serum showed that the surface was unstable with significant changes in the charge being measured. Dry TCP had a zeta potential of -9.3 mV, which shifted to -1.8 mV after soaking in water and to -27.6 mV in culture medium with serum. To clarify the effect of the time-dependent variation of the surface structure on growth and adhesion of anchorage-dependent animal cells, the zeta potential of ceramics in dry state was regulated from -11.5 mV to + 27.2 mV by means of silane coupling modification. After soaking in distilled water for six days, zeta potential of the modified TCPs shifted to between +7.5 mV and -7.6 mV, while they were between -9.9 mV and -23.7 mV in culture medium with serum, Concentrations of calcium and phosphate dissolved in distilled water and in culture medium showed the solubility of the ceramics was considerably high and depended on the pH of the surface layer. The suitable surface property for adhesion of L-929 cells was obtained by the most stable ceramics in the culture condition. In conclusion, the solubility of the thin surface layer of the carrier was considered to be the dominant factor in decreasing the adhesiveness of cells on TCP ceramics.