A Review on the Advances in Nanomaterials for Electrochemical Non-Enzymatic Glucose Sensors Working in Physiological Conditions

Although an enzymatic electrochemical biosensor is a major keystone in Diabetes Mellitus management, its replacement with a low-cost and stable non-enzymatic glucose sensor (NEGS) is of high interest to scientific and industrial fields. However, most NEGS for direct glucose electrooxidation (DGE) must be performed under extreme alkaline conditions, implying additional pretreatments before detection and a limited application for on-body, real-time monitoring. Thus, research on DGE in physiological conditions is fundamental to successfully translating the current NEGS into clinical applications. In physiological conditions, drawbacks such as low current, low selectivity, and poisoning appear due to the reduction of OH ions in neutral electrolytes and the presence of chloride ions in biofluids. Therefore, an increasing number of nanomaterials based on Pt, Au, and their nanocomposites have been proposed to improve the electrochemical performance. Additionally, transition metals such as Cu, Pd, Ni, or Co combined with high surface area supports have shown promising results in increasing catalytic sites for DGE. The molecular interaction of phenylboronic acid with glucose has also been demonstrated in neutral conditions. Overall, the present review summarizes the current strategies for DGE in physiological conditions and highlights the challenges still faced for further development of functional glucose NEGS.