Wiring of enzymes to electrodes by ultrathin conductive polyion underlayers: enhanced catalytic response to hydrogen peroxide.
Stable electroactive films were grown layer by layer on rough pyrolytic graphite electrodes featuring 4-nm underlayers of sulfonated polyaniline (SPAN) covered with a film containing myoglobin or horseradish peroxidase grown in alternating layers with poly(styrenesulfonate). The self-doped polyanionic SPAN layer, grown on a 2-nm polycation layer, was conductive between about 0.1 and -0.4 V vs SCE at pH 4.5. The enzyme films had the architecture PDDA/SPAN/(enzyme/PSS)3, where PDDA is poly(diallyldimethylammonium) ion. Comparisons of voltammetric measurements of electroactive protein with quartz crystal microbalance measurements of total protein showed that 90% or more of the protein was coupled to the electrode when the SPAN underlayer was present, as opposed to approximately 40% protein electroactivity when SPAN was absent. As a consequence of the highly efficient coupling between enzymes and electrode, the PDDA/SPAN/(enzyme/PSS)3 films exhibited a higher sensitivity for the electrochemical catalytic reduction of hydrogen peroxide. Amperometry at a rotating disk electrode at 0 V gave sensitivity for hydrogen peroxide up to 14 microA microM(-1) cm(-2) in the submicromolar concentration range and a detection limit of approximately 3 nM. Results suggest the future utility of ultrathin layers of conductive self-doping polyions in improving sensitivity of enzyme biosensors.
Yu
Xin
X
Department of Chemistry, Box U-60, University of Connecticut, Storrs, Connecticut 06269-3060, USA.
Sotzing
Gregory A
GA
Papadimitrakopoulos
Fotios
F
Rusling
James F
JF
D000818:Animals; D015374:Biosensing Techniques / Q000295:instrumentation* / Q000379:methods*; D002384:Catalysis; D004563:Electrochemistry; D004566:Electrodes; D006735:Horseradish Peroxidase / Q000737:chemistry / Q000378:metabolism; D006736:Horses; D006861:Hydrogen Peroxide / Q000378:metabolism*; D007477:Ions / Q000737:chemistry; D009211:Myoglobin / Q000737:chemistry / Q000378:metabolism
D007477:Ions; D009211:Myoglobin; D006861:Hydrogen Peroxide; D006735:Horseradish Peroxidase