Enhancement of Direct Electrocatalytic Activity of Horseradish Peroxidase on Polyaniline Nanotubes

Abstract

The advantages of nanotubes over compact conducting polymer films include the large surface area available for enzyme immobilization, facile diffusion of analyte molecules and enhanced conductivity. Heat treatment of PANI induces the formation of phenazine cross-links between PANI chains, which influences the electrocatalytic response of the immobilized enzymes. In this study, both polyaniline (PANI) bulk films and nanotubes were studied as a support for horseradish peroxidase (HRP). Two types of nanotubes, with diameters of 100 and 400 nm, were investigated. HRP was immobilized by physical adsorption or covalent bonding via the carbodiimide reaction. The influence of the heat treatment of PANI prior to enzyme immobilization on the electrochemical responses of the PANI/HRP electrodes was studied. The electrocatalytic current due to hydrogen peroxide (H 2 O 2 ) reduction was observed in all of the studied samples. However, the current values observed for HRP immobilized on PANI nanotubes with diameters of 100 nm (PANI/100 nm) were an order of magnitude higher than that of the bulk film. The electrocatalytic currents for the PANI/ 400 nm nanotubes had intermediate values between PANI/100 nm and the PANI bulk film. Linear responses to H 2 O 2 were observed over a wide concentration range for all of the HRP/PANI systems. The formation of phenazine cross-links due to the thermal treatment of PANI was confirmed from the Raman spectra. The cross-linking contributes to the enhanced mechanical stability of the PANI nanotubes. However, this cross-linking does not enhance significantly the electrocatalytic activity of the immobilized enzyme.

Nanoforest: Polyaniline Nanotubes Modified with Carbon Nano-Onions as a Nanocomposite Material for Easy-to-Miniaturize High-Performance Solid-State Supercapacitors

“…This band includes a less visible shoulder at 1192 cm −1 connected with C–H in-plane benzenoid ring bending. The signals at 1335 cm −1 and those near 1250 cm −1 are characteristic for charge carriers and correspond to delocalized polaronic units and ring deformation vibrations, respectively [57,58]. This indicates that the polymer nanotubes are in a conductive form.…”

Electrocatalytic Properties of Immobilized Heme Proteins: Basic Principles and Applications

“…Peroxidases were adsorbed on organic (lypopolissaccaride, polyaniline, DNA, glutaraldehyde) [158][159][160] or inorganic (titanium or manganese oxides) [161,162] components or directly included in carbon nanotubes or nanoparticles. These thoroughly studied enzymes act as electrocatalyst for the reduction of different substrates, mainly hydroperoxides.…”

“…Many substrates and different procedures are used to immobilize peroxidases on electrode (glassy carbon and graphite) surfaces. Peroxidases were adsorbed on organic (lypopolissaccaride, polyaniline, DNA, glutaraldehyde) [158][159][160] or inorganic (titanium or manganese oxides) [161,162] components or directly included in carbon nanotubes or nanoparticles. [60,145,163] Peroxidases show high versatility and good analytical responses (low detection limit and large linear range) towards hydroperoxides also under severe conditions like high temperatures.…”

Permselectivity and thickness-dependent ion transport properties of overoxidized polyaniline: a mechanistic investigation

“…Among various conducting polymers, polyaniline has been extensively investigated on account of its high conductivity, thermal stability and facile synthetic protocols. [1][2][3] Owing to its metal-like conductivity and polymeric properties, diverse applications of polyaniline (PANI) can be envisaged such as in sensors, 4 supercapacitors, 5 electrocatalysts, 6 batteries, 7 electrochromic devices, 8 corrosion inhibitors, 9 etc. The synthesis of PANI can be accomplished using chemical or electrochemical routes; electrochemical polymerization results in the formation of films on the electrodes and hence is especially convenient for analytical and catalytic applications.…”