Carbon nanotubes/polyethylenimine/glucose oxidase as a non-invasive electrochemical biosensor performs high sensitivity for detecting glucose in saliva

With the aim of improving the life quality for diabetics, we develop a novel electrode for the noninvasive glucose sensor which can determine the glucose levels in saliva. In this work, carbon nanotubes (CNTs) are directly grown on a fluorine-doped tin oxide (FTO) coated glass substrate through chemical vapor deposition, followed by the immobilization of glucose oxidase (GOx) via electrostatic force with the aid of polyethylenimine (PEI). The results confirm that the CNT forest can substantially enhance the charge transferability, and considerable quantities of GOx can be stably immobilized on the rough surface of the electrode because of the networked structure of the CNT forest. With a fast electron transfer rate and short electron transfer distance, both the current difference of the oxygen consumption and enzyme reduction reaction are detected for glucose sensor using the cyclic voltammetry method. The FTO-CNTs/PEI/GOx electrode exhibits the high sensitivity of 63.38 mu A/mMcm2 with a wide linear range of 70-700 mu M glucose. Furthermore, the FTO-CNTs/PEI/GOx electrode shows good stability as well as high selectivity towards glucose. Finally, the glucose sensing performance of the FTO-CNTs/ PEI/GOx electrode is investigated in artificial saliva, which exhibits great sensitivity even under high-viscosity conditions such as artificial saliva, thus, reveals excellent potential for use in practical applications.

Automated summary

In this research, a novel electrode was developed for noninvasive glucose sensing, which can determine glucose levels in saliva. The electrode consists of carbon nanotubes grown on a fluorine-doped tin oxide coated glass substrate, with glucose oxidase immobilized using polyethylenimine. The electrode demonstrated enhanced charge transferability and stable immobilization of glucose oxidase. It exhibited fast electron transfer rate, short electron transfer distance, and high sensitivity and stability towards glucose in artificial saliva. This research shows great potential for practical applications.