Contact angle and biocompatibility of sol‐gel prepared TiO 2 thin films for their use as semiconductor‐based cell‐viability sensors

We have investigated the surface, biocompatibility, and H 2 O 2 sensitivity of TiO 2 thin films prepared by sol‐gel technique, from the viewpoints of aptitude for a gate‐oxide film on field‐effect transistors (FETs) for cell‐viability sensors. The surface of TiO 2 thin films had nanometer‐scale roughness (approximately 1 nm in height), but was uniform and flat in micrometer scale. The contact angle of the TiO 2 thin films increases with time, when the TiO 2 /GaAs samples were preserved in air at room temperature, probably because of hydrophobic contaminates. A stretched exponential dependence fits well to the temporal evolution of the TiO 2 contact angle. Scattered data obtained in cell‐adhesion experiments show that the cell adhesion is mostly independent of the contact angle of the TiO 2 surfaces. In order to evaluate TiO 2 thin films for biosensor use, TiO 2 thin films were formed on two‐dimensional electron‐gas (2DEG) FETs as the gate‐oxide film. TiO 2 /2DEG‐FETs exhibit a high H 2 O 2 sensitivity up to 4.5 mV/µ M , whereas conventional ISFET (Ta 2 O 5 /Si‐FET)is insensitive to H 2 O 2 . Copyright © 2008 John Wiley & Sons, Ltd.