Nanohybrid Materials Consisting of Poly[(3‐aminobenzoic acid)‐co‐(3‐aminobenzenesulfonic acid)‐co‐aniline] and Multiwalled Carbon Nanotubes for Immobilization of Redox Active Cytochrome c

Abstract

The development of a new surface architecture for the efficient direct electron transfer of positively charged redox proteins is presented. For this reason different kinds of polyaniline terpolymers consisting of aminobenzoic acid (AB), aminobenzenesulfonic acid (ABS) and aniline (A) with different monomer ratios were synthesized. The P(AB‐ABS‐A) were grafted to the surface of multiwalled carbon nanotubes (MWCNTs). FTIR measurements prove the covalent binding to the carboxylic groups of the MWCNTs while conductivity tests show an increase in the conductivity of the nanohybrid in comparison to the polymers. The [MWCNT‐P(AB‐ABS‐A)] nanohybrids were used for the immobilization of redox active cytochrome c (cyt.c). The positively charged protein can electrostatically interact with the negatively charged nanohybrid. Cyclic voltammetry (CV) shows an increase in the protein loading on [MWCNT‐P(AB‐ABS‐A)] coupled to cysteamine modified gold electrodes in comparison to non‐grafted MWCNTs. A further increase in the sulfonation degree of P(AB‐ABS‐A) leads to an enhanced current output of the modified electrodes. The redox activity of the polymer decreases after the immobilization of the cyt.c on the nanohybrid. For the first time polymers covalently grafted to the surface of MWCNTs are used in a biosensor.

Polymer–Lipid Hybrid Membranes as a Model Platform to Drive Membrane–Cytochrome c Interaction and Peroxidase-like Activity

“…So far, in order to provide a better environment for cyt c to function, different electrodes which are mainly based on nanomaterials (e.g. carbon nanotubes, graphene and nanoparticles) have been used [40][41][42][43][44][45] . Nevertheless, these attempts might not be sufficient to preserve the whole cyt c activity.…”

“…For example, it is well known that functional properties of cytochrome c (cyt c ) were hampered because it adsorbed strongly on electrodes ( e.g., Pt, Hg, Au, and Ag) because this adsorption caused large conformational changes and denaturation. − Moreover, direct electron transfer between cyt c and unmodified electrode surface is slow due to undesired contact between the prosthetic group and the electrode . So far, in order to provide a better environment for cyt c to function, different electrodes which are mainly based on nanomaterials ( e.g., carbon nanotubes, graphene, and nanoparticles) have been used. − Nevertheless, these attempts might not be sufficient to preserve the whole cyt c activity. By forming planar membranes on solid support as a mean of electrode surface modification, (i) a natural biocompatible means of cyt c –substrate interactions and (ii) effective, highly dynamic platform to host biomolecules can be achieved. , Such a system improves the protein–membrane–substrate communication for the development of highly sensitive and efficient biosensors.…”

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

“…Such nanohybrids consisting of CNTs and polyaniline‐derivates have been synthesized 13,14 and used in a lactose biosensor 15. Immobilization of cytochrome c (cyt.c) on the negatively charged surface of a nanohybrid (MWCNT‐P(AB‐ABS‐A)) resulted in an increase in electroactive surface concentration of cyt.c in comparison to unmodified MWCNTs 16.…”

“…For the negatively charged nanohybrid the surface concentration at saturation was calculated to be either 3.1 pmol cm −2 ( n =6). For comparison, the surface concentration of cytochrome c (taking the size of 10.2 nm 2 ), immobilized on nanostructured surface, was reported to be 16.2 pmol cm −2 16.…”

Carboxylated or Aminated Polyaniline—Multiwalled Carbon Nanotubes Nanohybrids for Immobilization of Cellobiose Dehydrogenase on Gold Electrodes

“…By increasing the degree of sulfonation, the peak current of the redox protein could also be enhanced. The study showed that the immobilization of cyt c was possible and that a more efficient DET to the nanostructured electrode could be achieved [ 38 ].…”