Cu2O-Based Electrochemical Biosensor for Non-Invasive and Portable Glucose Detection

Abstract

Electrochemical voltammetric sensors are some of the most promising types of sensors for monitoring various physiological analytes due to their implementation as non-invasive and portable devices. Advantages in reduced analysis time, cost-effectiveness, selective sensing, and simple techniques with low-powered circuits distinguish voltammetric sensors from other methods. In this work, we developed a Cu₂O-based non-enzymatic portable glucose sensor on a graphene paste printed on cellulose cloth. The electron transfer of Cu₂O in a NaOH alkaline medium and sweat equivalent solution at very low potential (+0.35 V) enable its implementation as a low-powered portable glucose sensor. The redox mechanism of the electrodes with the analyte solution was confirmed through cyclic voltammetry, differential pulse voltammetry, and electrochemical impedance spectroscopy studies. The developed biocompatible, disposable, and reproducible sensors showed sensing performance in the range of 0.1 to 1 mM glucose, with a sensitivity of 1082.5 ± 4.7% µA mM^-1 cm^-2 on Cu₂O coated glassy carbon electrode and 182.9 ± 8.83% µA mM^-1 cm^-2 on Cu₂O coated graphene printed electrodes, making them a strong candidate for future portable, non-invasive glucose monitoring devices on biodegradable substrates. For portable applications we demonstrated the sensor on artificial sweat in 0.1 M NaOH solution, indicating the Cu₂O nanocluster is selective to glucose from 0.0 to +0.6 V even in the presence of common interference such as urea and NaCl.

Keywords: Cu2O nanomaterial; electrochemical sensor; glucose sensor; non-enzymatic sensor.

Figure 1

Schematic fabrication of the glucose sensor. (i) Cu₂O nanoclusters drop casted on the GCE for material study. (ii) Graphene paste printed on cellulose cloth with a Ag/AgCl RE. (iii) Modified WE with Cu₂O on the graphene printed cellulose substrate.

Figure 2

(a) XRD spectrum of simulated Cu₂O, synthesized powder Cu₂O, and WE drop casted with Cu₂O nanoclusters (Cu₂O PE). (b) SEM images of the Cu₂O drop casted on the PEs: (b) Cu₂O nanoclusters, (c) graphene paste and (d) EDS mapping of the interface between Cu₂O and the graphene paste with an inset of the SEM image. Green corresponds to Cu, blue to O, and red to C.

Figure 3

CV (a) and DPV (b) of Cu₂O nanoclusters on GCE with varying glucose concentrations (100–1000 µM) in 0.1 M NaOH. (c) Calibration curve at 0.35 V from DPV analysis.

Figure 4

CV (a) and DPV (b) of Cu₂O nanoclusters on printed WE with varying glucose concentrations (100–1000 µM) in 0.1 M NaOH. (c) Calibration curve at 0.35 V from DPV analysis.

Figure 5

Nyquist plot of 0.1 M NaOH with 100 µM glucose solution of (a) Cu₂O coated GCE with magnitude of impedance inset and (b) Cu₂O coated on PE with magnitude of impedance inset.

Figure 6

Electrochemical analysis of fully printed Cu₂O-based glucose sensors over a glucose concentration range of 100–700 µM. (a) CV and (b) DPV in 0.1 M NaOH. (c) CV and (d) DPV artificial sweat in 0.1 M NaOH.