Polyurethane-acrylate photocurable polymeric membrane for ion-sensitive field-effect transistor based urea biosensors

The development of a new electrochemical microsensor based on silicon technology with a photocurable enzyme membrane based on polyurethane acrylate is described. The use of photocurable polymers as the entrapping matrix for enzymes fulfils all the requirements expected for these materials without damaging the biological material. Additionally, the preparation of biosensor devices following this methodology is fast and simple, and this entails the main improvement shown by the new immobilisation method proposed here. The polymer used for enzyme immobilisation enhances the adhesion of the membrane to the previously silanised ion-sensitive field effect transistor (ISFET) gate and assures a long-term stability of more than one month. Additionally, this material provides a membrane deposition methodology compatible with photolithographic techniques allowing mass-production of low cost biosensors. The membrane has been optimised taking into account a good entrapment of the biological material and the effective transport of the substrate and the products through the membrane. After mixing the components of the prepolymer solution, a short exposure (30 s) to 365 nn W-radiation produced a polymeric membrane without damaging the enzyme. The calibration parameters for the sensors prepared compared well with other methods yielding a slope of 58 mV/dec and a linear range of 0.04-36.0 mM urea in a NH4Cl pH 5.6 solution. The response time (t 95%) was approximately 2 min. (C) 1999 Elsevier Science B.V. All rights reserved.