A biopolymer composite that catalyzes the reduction of oxygen to water

A biopolymer composite consisting of polypyrrole, ABTS, and laccase (PAL) was electrodeposited onto the surface of an electrode and was shown to catalyze the reduction of dioxygen to water under acidic conditions. The catalytic activity of this biopolymer composite is highest at pH 4, decreasing with increasing pH. The activity of laccase immobilized within this polymer composite was found to be higher than laccase dissolved in solution when methanol was present or at elevated temperatures.open283

Direct and mediated electrochemistry of peroxidase and its electrocatalysis on a variety of screen-printed carbon electrodes: amperometric hydrogen peroxide and phenols biosensor

This study compares the behaviour of direct and mediated electrochemistry of horseradish peroxidase (HRP) immobilised on screen-printed carbon electrodes (SPCEs), screen-printed carbon electrodes modified with carboxyl-functionalised multi-wall carbon nanotubes (MWCNT-SPCEs) and screen-printed carbon electrodes modified with carboxyl-functionalised single-wall carbon nanotubes (SWCNT-SPCEs). The techniques of cyclic voltammetry and amperometry in the flow mode were used to characterise the properties of the HRP immobilised on screen-printed electrodes. From measurements of the mediated and mediatorless currents of hydrogen peroxide reduction at the HRP-modified electrodes, it was concluded that the fraction of enzyme molecules in direct electron transfer (DET) contact with the electrode varies substantially for the different electrodes. It was observed that the screen-printed carbon electrodes modified with carbon nanotubes (MWCNT-SPCEs and SWCNT-SPCEs) demonstrated a substantially higher percentage (a parts per thousand 100 %) of HRP molecules in DET contact than the screen-printed carbon electrodes (a parts per thousand 60 %). The HRP-modified electrodes were used for determination of hydrogen peroxide in mediatorless mode. The SWCNT-SPCE gave the lowest detection limit (0.40 +/- 0.09 mu M) followed by MWCNT-SPCE (0.48 +/- 0.07 mu M) and SPCE (0.98 +/- 0.2 mu M). These modified electrodes were additionally developed for amperometric determination of phenolic compounds. It was found that the SWCNT-SPCE gave a detection limit for catechol of 110.2 +/- 3.6 nM, dopamine of 640.2 +/- 9.2 nM, octopamine of 3341 +/- 15 nM, pyrogallol of 50.10 +/- 2.9 nM and 3,4-dihydroxy-l-phenylalanine of 980.7 +/- 8.7 nM using 50 mu M H2O2 in the flow carrier