Optimization of the mixed urease/amphiphile Langmuir–Blodgett film and its application for biosensor development

The interaction of urease in subphase at a certain pH value with amphiphiles at the air–water interface leading to the formation of a stable mixed monolayer is of special interest due to its potential application in biosensor development. The dependence of stability of the mixed monolayers on various factors such as amphiphilic type (octadecylamine and behenic acid in this case), urease concentration in subphase, adsorption time, surface pressure and temperature of the subphase are studied in this paper. Octadecylamine, as amphiphilic molecule, shows a stronger associating ability with urease than behenic acid when urease concentration is kept in a suitable range of 4–12 mg/l. Mixed urease/octadecylamine monolayer can efficiently be transferred onto the hydrophobic surface of octadecylsilane-modified SiO2/Si substrate with an ideal transfer ratio. This is the crucial point to meet requirements for a reproducible deposition on a transducer surface, such as pH-ISFET (ion-sensitive field effect transistors), to achieve good biosensor characteristics.