Glucose oxidase immobilization onto carbon nanotube networking

TL;DR

This study presents a method for immobilizing glucose oxidase onto carbon nanotube networks using a molecular interface, enhancing enzyme localization and activity for biosensor applications.

Contribution

The paper introduces a covalent immobilization technique of glucose oxidase on carbon nanotubes via a PSE molecular interface, improving enzyme stability and localization.

Findings

Successful enzyme immobilization confirmed by AFM imaging.

Resonance Raman spectra indicate effective molecular isolation.

Conductivity measurements show maintained network properties.

Abstract

When elaborating the biosensor based on single-walled carbon nanotubes (SWNTs), it is necessary to solve such an important problem as the immobilization of a target biomolecule on the nanotube surface. In this work, the enzyme (glucose oxidase (GOX)) was immobilized on the surface of a nanotube network, which was created by the deposition of nanotubes from their solution in 1,2-dichlorobenzene by the spray method. 1-Pyrenebutanoic acid succinimide ester (PSE) was used to form the molecular interface, the bifunctional molecule of which provides the covalent binding with the enzyme shell, and its other part (pyrene) is adsorbed onto the nanotube surface. First, the usage of such a molecular interface leaves out the direct adsorption of the enzyme (in this case, its activity decreases) onto the nanotube surface, and, second, it ensures the enzyme localization near the nanotube. The comparison of the resonance Raman (RR) spectrum of pristine nanotubes with their spectrum in the PSE environment evidences the creation of a nanohybrid formed by an SWNT with a PSE molecule which provides the further enzyme immobilization. As the RR spectrum of an SWNT:PSE:GOX film does not essentially differ from that of SWNT:PSE ones, this indicates that the molecular interface (PSE) isolates the enzyme from nanotubes strongly enough. The efficient immobilization of GOX along the carbon nanotubes due to PSE is confirmed with atom-force microscopy images. The method of molecular dynamics allowed us to establish the structures of SWNT:PSE:GOX created in the aqueous environment and to determine the interaction energy between hybrid components. In addition, the conductivity of the SWNT network with adsorbed PSE and GOX molecules is studied.