STUDIES TOWARDS A DISPOSABLE SCREEN-PRINTED AMPEROMETRIC BIOSENSOR FOR PROGESTERONE

A screen-printed carbon electrode (SPCE) has been investigated as the base transducer for a disposable amperometric progesterone biosensor. The biorecognition element was a monoclonal sheep anti-progesterone an tibody (mAb). This was immobilized onto the transducer by interaction with a layer of rabbit IgG which had been previously coated onto the S PCE; optimum conditions for these loadings were deduced experimentally . The device was employed in a competitive assay using alkaline phosph atase-labelled progesterone. Three possible substrates for the enzyme were considered, namely, phenyl phosphate, phenolphthalein phosphate a nd 4-aminophenol phosphate. Cyclic voltammetry and amperometry were ca rried out on the corresponding aromatic phenols and phenol itself was found to give the best electrochemical characteristics; consequently, phenyl phosphate was employed as the substrate. Chronoamperometry was used to measure the phenol produced by the reaction of bound enzyme-la belled progesterone and substrate. The chronoamperometric response was dependent on unlabelled progesterone over at least three orders of ma gnitude with a detection limit of about 1 x 10(-9) mol/dm(3). This sug gests that the device may have applications for the analysis of biolog ical fluids. (C) 1997 Published by Elsevier Science Limited.