An ISFET-based penicillin sensor with high sensitivity, low detection limit and long lifetime

By choosing an optimal pH-sensitive transducer material and a low capacity polymix buffer, excellent working characteristics were achieved for a penic illin-sensitive field-effect transistor (PenFET) with adsorptively immobili sed penicillinase. The developed PenFET possesses a high sensitivity of 120 +/- 10 mV/mM in the concentration range of 0.05-1 mM penicillin G, a low d etection limit of 5 muM, a small hysteresis of less than 4 mV and a long li fetime of more than 1 year. For the PenFET a temperature-independent workin g point was found. A simple biosensor regeneration in the case of loss of t he enzyme activity is experimentally demonstrated. A pH ISFET/PenFET dual c hip is developed and investigated in order to eliminate disturbing factors such as temperature and drift influences as well as the possible variation of the pH of the bulk solution. (C) 2001 Elsevier Science B.V. All rights r eserved.