The optimization of enzyme immobilization at Au-Ti nanotextured platform and its impact onto the response towards glucose in neutral media

The market of non-invasive glucose sensors is drastically growing due to increasing number of people suffering from diabetes. Therefore, there is a significant need for any improvement in the field of biosensors that can be used for monitoring glucose level in human body. In recent years the emphasis is put onto the modification of electrode material with enzymes possessing recognition centre specific towards particular molecules. In this work, the nanoscale Au-Ti heterostructures functionalized with glucose oxidase is reported. Au-Ti material is prepared by anodization of Ti foil, chemical etching, thin Au layer sputtering and finally thermal treatment under continuous regime. The formation of dimples as well as the single Au nanoparticle per each structure dimple was revealed by field emission scanning electron and atomic force microscopies. The surface of obtained material is modified with glucose oxidase enzyme by three immobilization methods: covalent bonding, adsorption and cross-linking leading to selection of the most optimized electrode preparation process. In order to confirm enzyme presence and to describe the chemical state of elements, x-ray photoelectron spectroscopy measurements were performed indicating the complete coverage of Au-Ti material by the enzyme layer. The obtained electrodes were tested in 0.1 M phosphate buffer saline with an addition of glucose using cyclic and differential pulse voltammetries. The determined linear range of 0.05-3.05 mM and detection limit of 7.61 mu M satisfy the demands for glucose detection in human body fluids, for example interstitial fluid and sweat. Moreover, no impact onto the electrode response is observed for typical interfering species that is of key importance for further application.