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 penicillin-sensitive field-effect transistor (PenFET) with adsorptively immobilised 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 detection limit of 5 μM, a small hysteresis of less than 4 mV and a long lifetime of more than 1 year. For the PenFET a temperature-independent working point was found. A simple biosensor regeneration in the case of loss of the enzyme activity is experimentally demonstrated. A pH ISFET/PenFET dual chip 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.