A dual enzyme functionalized nanostructured thulium oxide based interface for biomedical application

In this paper, we present results of the studies related to fabrication of a rare earth metal oxide based efficient biosensor using an interface based on hydrothermally prepared nanostructured thulium oxide (n-Tm₂O ₃). A colloidal solution of prepared nanorods has been electrophoretically deposited (EPD) onto an indium-tin-oxide (ITO) glass substrate. The n-Tm₂O₃ nanorods are found to provide improved sensing characteristics to the electrode interface in terms of electroactive surface area, diffusion coefficient, charge transfer rate constant and electron transfer kinetics. The structural and morphological studies of n-Tm₂O₃ nanorods have been carried out by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) spectroscopic techniques. This interfacial platform has been used for fabrication of a total cholesterol biosensor by immobilizing cholesterol esterase (ChEt) and cholesterol oxidase (ChOx) onto a Tm ₂O₃ nanostructured surface. The results of response studies of the fabricated ChEt-ChOx/n-Tm₂O₃/ITO bioelectrode show a broad linear range of 8-400 mg dL^-1, detection limit of 19.78 mg (dL cm^-2)^-1, and high sensitivity of 0.9245 μA (mg per dL cm^-2)^-1 with a response time of 40 s. Further, this bioelectrode has been utilized for estimation of total cholesterol with negligible interference (3%) from analytes present in human serum samples. The utilization of this n-Tm₂O₃ modified electrode for enzyme-based biosensor analysis offers an efficient strategy and a novel interface for application of the rare earth metal oxide materials in the field of electrochemical sensors and bioelectronic devices.