Improving the Environment for Immobilized Dehydrogenase Enzymes by Modifying Nafion with Tetraalkylammonium Bromides

Abstract

Recent research in our group has shown that mixture-casting Nafion with quaternary ammonium bromides can increase the electrochemical flux of redox couples through the membrane and allow for larger redox species to diffuse to the electrode surface. The research has also suggested that when these salts are cast with Nafion micellar pore size is changing. Therefore, it was proposed that the quaternary ammonium salts could be employed to tailor the structure of the Nafion membrane for immobilizing enzymes in the polymer. For cations with a high affinity for the sulfonic acid groups of Nafion, the modified structure of Nafion can also help to stabilize the enzyme and increase activity by providing a protective outer shell and an ideal chemical environment that resists a decrease in pH within the pore structure. This research examines the ability to immobilize dehydrogenase enzymes in Nafion that has been modified with quaternary ammonium bromides. Fluorescence assays, fluorescence microscopy, and cyclic voltammetric studies were employed to analyze the ability to immobilize an enzyme within the membrane, to determine the activity of the immobilized enzyme and to examine the transport of coenzyme within the membrane. Dehydrogenase enzymes immobilized in tetrabutylammonium bromide/Nafion membranes have shown high catalytic activity and enzyme active lifetimes of greater than 45 days. A variety of dehydrogenase enzymes have been successfully immobilized in the membrane, including: alcohol dehydrogenase, aldehyde dehydrogenase, glucose dehydrogenase, and lactic dehydrogenase.

Operational Stability Assays for Bioelectrodes for Biofuel Cells: Effect of Immobilization Matrix on Laccase Biocathode Stability

“…51 TBAB modified Nafion has previously been shown to provide stabilizing properties when immobilizing enzymes, while allowing ion conductivity. 52 Polyamines, specifically poly-ethylenimines (PEI), are a group of polymers that have been shown to cross-link in the presence of biological surfaces, which can assist in stabilization and/or immobilization of biomolecules on surfaces. 53 Branched PEIs have been shown to adsorb onto the surface of CNTs.…”

Pyruvate/Air Enzymatic Biofuel Cell Capable of Complete Oxidation

“…Because our enzymatic system involves a variety of dehydrogenases, TBAB was the quaternary ammonium bromide salt employed in modifying the Nafion membrane as previous research has shown that it is ideal for immobilization of the majority of dehydrogenases. [9][10][11] The TBAB-modified Nafion membrane was formed in a two-step process. The first step was to cast a suspension of Nafion with TBAB dissolved in suspension.…”

Controlled Deposition of Structured Polymer Films: Chemical and Rheological Factors in Chitosan Film Formation

“…Nafion is currently the archetype material for and lactic dehydrogenases) in a tetraalkylammonium bromide modified Nafion membrane. 10,11 Although Nafion is capable of immobilizing a variety of enzymes, it is expensive and is lacks biocompatibility and biodegradability. 5 Chitosan is, therefore, an ideal alternative to Nafion as it is less expensive, biodegradable and has better biocompatibility.…”