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 0.03M pyrrole, 50U/mL P'nase, 0.01M penicillin, applied current density of 0.9mA/cm² and a polymerisation time of 40s. The optimum conditions for the formation of the outer layer of the bilayer were: (a) 0.1M Py, 19U/mL P'nase, 0.01M pen, current density of 0.9mA/cm² and a polymerisation time of 40s. The minimum detectable penicillin concentration with the bilayer potentiometric biosensor was 0.3μM and the linear concentration range was 7.5-146μM. The average percentage recovery of penicillin that was found in amoxycillin 500mg was 113±24%. The determination of penicillin in milk was fraught with problems of non-specific binding of penicillin to the milk.