A wearable sensor integrating a MXene-PLL-GOx-modified electrode and a Janus nanofibrous membrane for electrochemical monitoring of sweat glucose.

Abstract

MXene is a two-dimensional transition metal carbide with large specific surface area, good conductivity, and outstanding biocompatibility, which can be integrated with electrochemical devices, significantly enhancing the sensing performance. Herein, we present a wearable electrochemical sensor based on MXene composites modified electrode and Janus nanofibrous membranes for active sweat collection and precise detection of sweat glucose. Poly-l-lysine (PLL) is highly positively charged because of the -NH3+ groups, which acts as the crosslinker to bond MXene and glucose oxidase (GOx, containing -COO- groups) both negatively charged, forming a functional composite with high catalytic activity for glucose sensing. In this way, GOx was efficiently immobilized on the MXene nanosheets and then deposited on the screen-printed carbon electrode (SPCE). The intermediate H2O2 from enzymatic glucose oxidation was catalytically decomposed by MXene into H2O and O2. The recycled O2 further accelerated the enzymatic reaction on the SPCE. PU/PVA Janus nanofibrous membrane was prepared through electrospinning for active and effective sweat collection due to the unidirectional moisture conduction from its hydrophobic/hydrophilic side. The modified SPCE was integrated with the Janus nanofibrous membrane to fabricate a wearable sweat sensor, with the sensitivities of 16.70 μA mM-1 cm-2 for 0∼300 μM glucose levels, with a detection limit of 24.35 μM. The sensor also showed good stability, selectivity, and reproducibility, providing a new strategy for non-invasive sweat glucose monitoring.