Fabrication of enzyme-based coatings on intact multi-walled carbon nanotubes as highly effective electrodes in biofuel cells

Abstract

CNTs need to be dispersed in aqueous solution for their successful use, and most methods to disperse CNTs rely on tedious and time-consuming acid-based oxidation. Here, we report the simple dispersion of intact multi-walled carbon nanotubes (CNTs) by adding them directly into an aqueous solution of glucose oxidase (GOx), resulting in simultaneous CNT dispersion and facile enzyme immobilization through sequential enzyme adsorption, precipitation, and crosslinking (EAPC). The EAPC achieved high enzyme loading and stability because of crosslinked enzyme coatings on intact CNTs, while obviating the chemical pretreatment that can seriously damage the electron conductivity of CNTs. EAPC-driven GOx activity was 4.5- and 11-times higher than those of covalently-attached GOx (CA) on acid-treated CNTs and simply-adsorbed GOx (ADS) on intact CNTs, respectively. EAPC showed no decrease of GOx activity for 270 days. EAPC was employed to prepare the enzyme anodes for biofuel cells, and the EAPC anode produced 7.5-times higher power output than the CA anode. Even with a higher amount of bound non-conductive enzymes, the EAPC anode showed 1.7-fold higher electron transfer rate than the CA anode. The EAPC on intact CNTs can improve enzyme loading and stability with key routes of improved electron transfer in various biosensing and bioelectronics devices.

Photobiocatalysis: Activating Redox Enzymes by Direct or Indirect Transfer of Photoinduced Electrons

“…Fore xample,c ross-linking of glucose oxidase on carbon nanotubes led to superior stability of the enzyme over 270 days. [199] TheR OS generated during photosensitization may damage enzyme prosthetic groups and amino acid residues,s oi ti sn ecessary to minimize ROS formation through simplified and efficient electron transfer. Spatial separation of enzymes from awater oxidation environment in aP EC platform will protect the enzymes from potential damage caused by oxygen and ROS.O vercoming these challenges through further studies should open anew avenue in sustainable and scalable biotransformation.…”

Inulinase immobilization on polyethylene glycol/polypyrrole multiwall carbon nanotubes producing a catalyst with enhanced thermal and operational stability

“…Kim et al, 2009 [36] have shown successfully achieved immobilization of HRP on MWCNTs using succinimidyl ester as a cross-linker; while Garlet et al, 2014 [24] have used the oxidized MWCNTs containing carboxylic groups (-COOH) for non-covalent inulinase immobilization and reported very fast and highly efficient adsorption of the enzyme into immobilized formulation. On contrary, Kim et al [45] reported a simple immobilization of glucose oxidase on intact MWCNTs by adding them directly into an aqueous enzyme solution, resulting in simultaneous CNT dispersion and facile enzyme immobilization through sequential enzyme adsorption, precipitation, and crosslinking by glutaraldehyde. In more recent study, Singh et al [3] used modified MWCNTs with 3-aminopropyl-triethoxysilane to generate amino-terminated surfaces for inulinase from Penicillium oxalicum immobilization and obtained maximal inulinase activity of 60.7% and immobilization yield of 74.4%, while the enzyme lost 28% of its initial activity after the tenth cycle.…”

“…On contrary, Kim et al. reported a simple immobilization of glucose oxidase on intact MWCNTs by adding them directly into an aqueous enzyme solution, resulting in simultaneous CNT dispersion and facile enzyme immobilization through sequential enzyme adsorption, precipitation, and crosslinking by glutaraldehyde. In more recent study, Singh et al.…”

Biomass based bio-electro fuel cells based on carbon electrodes: an alternative source of renewable energy

“…Carbon derivatives have their unique combination of optical, mechanical, electrical and thermal properties which makes them widely being used in drug delivery, biosensors, nanoscale electronics and electron emitting devices etc. The characteristic features of high electronic conductivity with large surface area, nanoscale size, corrosion resistance of carbon derivatives [59][60][61][62][63] reduces the weight, size and cost of electrodes and makes them important in fuel cell applications, such as the ballistic electronic transport in carbon derivatives [64][65][66] enables them to carry a large amount of current without causing heating of the system. Figure 1 shows the carbon nanomaterials significantly being used for fuel cells.…”