Non-invasive smartphone-based saliva glucose sensing system using CuO NPs/MWCNTs composite-modified screen-printed electrodes

To address the limitations of traditional invasive glucose monitoring, including pain, infection risk, and poor patient compliance, this study develops a non-invasive, smartphone-based electrochemical sensing system for saliva glucose detection using a CuO NPs/MWCNTs composite-modified screen-printed electrode. The CuO nanoparticles (CuO NPs) were derived from copper metal-organic frameworks (Cu-MOFs) via high-temperature calcination, yielding a material with a high specific surface area and abundant pore structures that provide numerous glucose-reactive sites. Given the low glucose concentration in saliva, multi-walled carbon nanotubes (MWCNTs) were further incorporated to enhance the electrochemical performance. The developed sensor exhibited excellent glucose response in 0.1 M NaOH, with a wide linear range of 0.05–3 mM, a sensitivity of 0.51 mA mM −1  cm −2 , and a low detection limit of 8.94 μM (S/N = 3). Furthermore, the sensor demonstrates outstanding repeatability, long-term stability, and good anti-interference capability. In practical saliva sample tests, the system successfully tracked dynamic changes in human saliva glucose after oral glucose intake, showing good consistency with blood glucose trends. These results highlight the feasibility and preliminary potential of this platform for non-invasive glucose trend monitoring, with clinical validation in diabetic populations reserved for future work.