Journal
ANALYTICAL CHEMISTRY
Volume 75, Issue 17, Pages 4565-4571Publisher
AMER CHEMICAL SOC
DOI: 10.1021/ac034188r
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- NIEHS NIH HHS [ES03154] Funding Source: Medline
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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 similar to40% 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 muA muM(-1) cm(-2) in the submicromolar concentration range and a detection limit of similar to3 nM. Results suggest the future utility of ultrathin layers of conductive self-doping polyions in improving sensitivity of enzyme biosensors.
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