Peroxide-Dependent Analyte Conversion by the Heme Prosthetic Group, the Heme Peptide “Microperoxidase-11” and Cytochrome c on Chitosan Capped Gold Nanoparticles Modified Electrodes

Abstract

In view of the role ascribed to the peroxidatic activity of degradation products of cytochrome c (cyt c) in the processes of apoptosis, we investigate the catalytic potential of heme and of the cyt c derived heme peptide MP-11 to catalyse the cathodic reduction of hydrogen peroxide and to oxidize aromatic compounds. In order to check whether cyt c has an enzymatic activity in the native state where the protein matrix should suppress the inherent peroxidatic activity of its heme prosthetic group, we applied a biocompatible immobilization matrix and very low concentrations of the co-substrate H2O2. The biocatalysts were entrapped on the surface of a glassy carbon electrode in a biocompatible chitosan layer which contained gold nanoparticles. The electrochemical signal for the peroxide reduction is generated by the redox conversion of the heme group, whilst a reaction product of the substrate oxidation is cathodically reduced in the substrate indication. The catalytic efficiency of microperoxidase-11 is sufficient for sensors indicating HRP substrates, e.g., p-aminophenol, paracetamol and catechol, but also the hydroxylation of aniline and dehalogenation of 4-fluoroaniline. The lower limit of detection for p-aminophenol is comparable to previously published papers with different enzyme systems. The peroxidatic activity of cyt c immobilized in the chitosan layer for catechol was found to be below 1 per mill and for p-aminophenol about 3% as compared with that of heme or MP-11.

Direct Electron Transfer and Bioelectrocatalysis by a Hexameric, Heme Protein at Nanostructured Electrodes

“…The surface coverage ( Γ ), determined from the peak areas of the cyclic voltammograms, is around 43 pmol cm −2 . It is smaller than on gold nanoparticle modified gold electrodes (387 pmol cm −2 ) 18 or the value for MWCNT‐modified glassy carbon electrodes (2.7 nmol cm −2 ) 20.…”

“…The heterogenous electron transfer constant ( k s ), calculated by the method of Laviron 21, is 15.4 s −1 . It is higher than on MWCNT‐modified electrodes (2.9 s −1 ) 20 and only sligthly lower than on gold nanoparticle‐modified electrodes (23.7 s −1 ) 18.…”

“…The formal potential is around 60 mV more cathodic than that for hemin entrapped in chitosan 18 but comparable with hemin on pyrolytic graphite electrodes at −380 mV (vs. Ag/AgCl) 19 or on MWCNT modified glassy carbon electrodes (−340 mV; vs. Ag/AgCl) 20. The foot print of hemin is 2.38 nm 2 .…”

Enhancement of the Electrocatalytic Activity of Thienyl‐Substituted Iron Porphyrin Electropolymers by a Hangman Effect

“…These so‐called Hangman porphyrins were shown to exhibit higher catalytic activities than porphyrins lacking the acid hanging group . Various approaches have been reported for immobilization of hemin (ferric chloride heme) and its derivatives by e. g. attachment to self‐assembled monolayers (SAM),, nanoparticles or nanotubes as well as electropolymerization of porphyrin monomers . The latter technique offers the possibility of controlling the film deposition via applied potentials and polymerization duration…”

Electrochemical Based Biosensors

“…This Special Issue has received and published manuscripts relating to electrochemical based biosensors [ 1 , 2 , 3 , 4 , 5 , 6 ]. The recognition process or the reaction mechanism that these biosensors employ include ZnO based enzymatic reaction, carbon nano-tube enzymatic-gelatin reaction and whole cell system.…”