Electrochemical studies of glucose oxidase immobilized on glutathione coated gold nanoparticles

Glutathione (L-gamma-glutamyl-L-cysteinyl-L-glycine; GSH) forms a surface monolayer on gold nanoparticles by tethering via sulfur bonds (Au:GSH). In the present study, glucose oxidase (GOx; EC 1.1.3.4) was immobilized by covalent chemical coupling reactions on to Au:GSH nanoparticles and the enzyme coupled nanoparticles formed a stable colloid (stable for several weeks) in water. The immobilized enzyme was investigated for electrochemical characteristics to monitor the FAD (prosthetic group of the GOx) redox potentials. Various concentrations of substrate (glucose) were added to check the oxidation characteristics. It was observed that with increase in substrate concentrations, the oxidation rate increased proportionally with the current. The present study demonstrated that GOx was effectively coupled to the gold nanoparticle (Au:GSH). The coupled nanoparticle system could be used in a potential biosensor application. Similarly, other enzymes (e.g., horseradish peroxidase) could be immobilized to the Au:GSH nanoparticles via the peptide arm (GSH) to achieve the desired characteristics needed for a specific application in biosensor.