Fabrication of a Single Layer and Bilayer Potentiometric Biosensors for Penicillin by Galvanostatic Entrapment of Penicillinase into Polypyrrole Films

A single layer and bilayer potentiometric biosensors for the detection of penicillin have been developed. The favourable conditions that were established for the polypyrrole-penicillinase ((PPy-P'nase) single layer biosensor were 0.03 M pyrrole, 50 U/mL P'nase, 0.01 M penicillin, applied current density of 0.9 mA/cm(2) and a polymerisation time of 40 s. The optimum conditions for the formation of the outer layer of the bilayer were: (a) 0.1 M Py, 19 U/mL P'nase, 0.01 M pen, current density of 0.9 mA/cm(2) and a polymerisation time of 40 s. The minimum detectable penicillin concentration with the bilayer potentiometric biosensor was 0.3 mu M and the linear concentration range was 7.5-146 mu M. The average percentage recovery of penicillin that was found in amoxycillin 500 mg was 113 +/- 24%. The determination of penicillin in milk was fraught with problems of non-specific binding of penicillin to the milk.