Chemical and biological sensors based on electrochemical detection using conducting electroactive polymers

The electrochemical behavior of composites of conducting electroactive polyaniline (PAn) and polypyrrole (PPy) formulated within cross-linked hydrogel networks was investigated by cyclic voltammetry and electrochemical impedance spectroscopy (EIS). Composite PAn gels displayed similar anodic charge density compared to the pristine conducting polymer (80 mC/cm(2) and 84 mC/cm(2), respectively), suggesting a similar degree of electroactivity between the two systems. Composite gels of PAn displayed fast cation transport with K+ diffusivity (D-appt= 5.31x10(-7) cm(2)s(-1)) that were three orders of magnitude larger than that of pristine PAn (D-appt=3.12x10(-10) cm(2)s(-1)), while PPy composite gels showed similar ferrocene anion diffusivity (D-appt=7.05x10(-5) cm(2)s(-1)) compared to electropolymerized PPy (D-appt=6.54x10(-5) cm(2)s(-1)). The electrochemical interactions between CYP2D6, a cytochrome P450 isoenzyme, and fluoxetine mediated by electroactive polyaniline films on glassy carbon electrodes (GCEs) were investigated. Cyclic voltammograms indicate that PAn is an effective mediator of CYP2D6 activity under anaerobic conditions. An analytical interrogation methodology based on small-amplitude, pulsed DC was developed and incorporated into the Electroconductive Polymer Sensor Interrogation System (EPSIS). Polypyrrole membranes were rendered biospecific by either copolymerization of pyrrole (Py) with 4-(1-pyrrolyl) butyric acid (4PyBA), followed by direct conjugation with 5-(biotinamido)pentyl amine (5BPA), or by reacting 4PyBA with 5BPA to form pyrrolyl-biotin conjugates. The biotinylated PPy was made responsive to glucose or urea by exploiting strong biotin-streptavidin binding to either streptavidin-glucose oxidase or biotin-urease conjugates. These bioactive conducting polymer membranes were demonstrated as conductimetric glucose and urea biosensing layers using the EPSIS. The rate of conductivity of the bioactive PPy membranes was observed to double upon increasing glucose concentration from 100 muM (4x10(-6) S cm(-1) s(-1)) to 600 muM (9x10(-6) S cm(-1) s(-1)).