Abstract
A stable Fe(4-TMPyP)-DNA-PADDA (FePyDP) film was characterized on pyrolytic graphite electrode (PGE) or an indium-tin oxide (ITO) electrode through the supramolecular interaction between water-soluble iron porphyrin (Fe(4-TMPyP)) and DNA template, where PADDA (poly(acrylamide-co-diallyldimethylammonium chloride) is employed as a co-immobilizing polymer. Cyclic voltammetry of FePyDP film showed a pair of reversible Fe(III)/Fe(II) redox peaks and an irreversible Fe(IV)/Fe(III) peak at –0.13 V and +0.89 vs. Ag|AgCl in pH 7.4 PBS, respectively. An excellent catalytic reduction of NO was displayed at –0.61 V vs. Ag|AgCl at a FePyDP film modified electrode. Chronoamperometric experiments demonstrated a rapid response to the reduction of NO with a linear range from 0.1 to 90 μM and a detection limit of 30 nM at a signal-to-noise ratio of 3. On the other hand, it is the first time to apply high-valent iron porphyrin as catalyst at modified electrode for NO catalytic oxidation at +0.89 vs. Ag|AgCl. The sensor shows a high selectivity of some endogenous electroactive substances in biological systems. The mechanism of response of the sensors to NO is preliminary studied.