Hepatocyte spheroid formation on a titanium dioxide gel surface and hepatocyte long-term culture

The cell morphology and expression of differentiated functions of primary rat hepatocytes on a titanium dioxide (TiO₂) gel surface were investigated. Polystyrene culture dishes were coated with TiO₂ gel by spin-coating an ethanol solution of titanium n-butoxide, hydrolyzing in a humidity chamber and drying with nitrogen gas. The TiO₂ gel layer formed on the polystyrene dishes was transparent and robust, and its surface was quite flat. Rat hepatocytes inoculated on the TiO₂ gel-coated polystyrene dishes gradually accumulated with increasing culture time, and then spontaneously formed many hepatocyte spheroids at 90 ± 21 μm diameter from about 3 days of culture. The diameter of the spheroids increased during the culture, and was 151 ± 43 μm at 14 days of culture. Ammonia removal and albumin secretion by hepatocytes on the TiO₂ gel-coated polystyrene dishes were maintained at a high level for at least 14 days of culture compared with on a type I collagen-coated dish and a non-coated polystyrene dish. These results indicate that TiO₂ gel is an adequate material for hepatocyte spheroid formation and long-term culture of spheroids.