Contact angle and biocompatibility of sol‐gel prepared TiO2 thin films for their use as semiconductor‐based cell‐viability sensors

Abstract

AbstractWe have investigated the surface, biocompatibility, and H2O2 sensitivity of TiO2 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 TiO2 thin films had nanometer‐scale roughness (approximately 1 nm in height), but was uniform and flat in micrometer scale. The contact angle of the TiO2 thin films increases with time, when the TiO2/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 TiO2 contact angle. Scattered data obtained in cell‐adhesion experiments show that the cell adhesion is mostly independent of the contact angle of the TiO2 surfaces. In order to evaluate TiO2 thin films for biosensor use, TiO2 thin films were formed on two‐dimensional electron‐gas (2DEG) FETs as the gate‐oxide film. TiO2/2DEG‐FETs exhibit a high H2O2 sensitivity up to 4.5 mV/µM, whereas conventional ISFET (Ta2O5/Si‐FET)is insensitive to H2O2. Copyright © 2008 John Wiley & Sons, Ltd.