Side-Gate-FET Test Strips for Invasive and Non-Invasive Saliva-Based Glucose Monitoring Using GO-Catalyzed CuO-ZnO Hollow Spheres

This article reports the development of saliva glucose biosensors utilizing GO-catalyzed CuO-ZnO hollow spheres. We have created six sensors with the same design of noninvasive biosensors to monitor the glucose levels in saliva, employing a field-effect transistor (FET) architecture. Using the hydrothermal method, we synthesized the composite GO-catalyzed CuO-ZnO hollow spheres with varying concentrations of graphene oxide (GO) to serve as the FET channel. The proposed Bio-FETs exhibit a low limit of detection (LOD) of $0.001~\mu $ M, a high sensitivity of $1600~\mu \text {A}\cdot \text {mM}^{-{1}}$ , and promising reproducibility, stability, and repeatability. We also developed a mobile-enabled device that facilitates convenient saliva glucose monitoring. This article provides an in-depth discussion of the fabrication processes, material characterizations, and performance metrics of the Bio-FETs, emphasizing their potential for accurate and reliable noninvasive health monitoring marking an advancement in the technology for monitoring glucose levels in real saliva.