Hajime Nagae

Effects of the surface wettability and zeta potential of bioceramics on the adhesiveness of anchorage-dependent animal cells

Abstract Using calcium phosphate ceramics that have high biocompatibility with the living body, the effects of the surface characteristics of the bioceramics on cell adhesiveness were investigated. In the case of carriers with contact angles from 35° to 60°, the cell adhesiveness increased according to the increase in the wettability. Measurement of the zeta potentials of HAP-TCP sinters showed that these bioceramics had negative potentials from −2 mV to −6 mV. Electrochemical analysis suggested that the initial cell anchoring ratio (Ria) and adhesive strength (Fa,enz) were affected by the surface ionic condition of the ceramic material. To clarify the effects of the surface potential of the ceramics on cell adhesiveness, the ceramic surface was modified chemically by means of various silane coupling reagents. The surface potential was regulated from −20 mV to +24 mV. Using these ceramics, the affinity and adhesiveness of the cells to the ceramics were found to be dominantly regulated by the surface potential. A negative potential was effective in increasing the adhesiveness, even though living cells have negative charges.

Hydrothermal synthesis of plate-like hydroxyapatite crystals

A precursor hydroxyapatite (HAp) slurry prepared from CaHPC4 2H2O and CaCO3 was treated under hydrothermal conditions at 180°C for 5 hours with various alcohols; i.e. methanol, ethanol, propanol, butanol, ethylene glycol and glycerol. The products were identified as carbonate-containing HAp by X-ray diffraction and IR spectrometry. TEM showed that crystals obtained from the slurry prepared in the absence of alcohol were rod-like, about 20nm in width and 50nm in length. In contrast, the products from slurries containing alcohol were found to be a mixture of plate-like and rod-like crystals. The ratio of plate-like to rod-like crystals increased with increasing alcohol content in the slurry. When 50wt% of monohydroxy or dihydroxy alcohol was used, the shape of products was plate-like. The shape of the crystals depended on the number of hydroxy groups in the particular alcohols used, but was independent of the length of the hydrocarbon chain in the alcohol.