NiOX Template-Grown Ni-MOF-Coated Carbon Paper Electrode Embedded Extended Gate Field Effect Transistor for Glucose Detection in Saliva: En Route toward the Noninvasive Diagnosis of Diabetes Mellitus

Our present work focuses on the development of nickel oxalate (NiOX) template-assisted growth of a nickel–metal organic framework (Ni-MOF) with sheetlike morphology on carbon paper (CP) electrode for the noninvasive detection of glucose. We have utilized an extended gate field effect transistor (EGFET) where the Ni-MOF/CP electrode serves as the extended gate of a commercial n-type metal oxide semiconductor FET for sensing glucose. The electrode detects glucose concentrations ranging from 20 μM to 1.47 mM. The sensor operates at a voltage of 0.7 V in the physiologically relevant electrolyte of phosphate-buffered saline (PBS) with a response time of less than 5 s. The sensitivity is calculated as 86 μA mM^–1 cm^–2 from the linear region of the sensor response to the glucose concentration (20 μM to 0.27 mM). Also, Ni-MOF/CP has shown a good selective response toward glucose against uric acid, sucrose, fructose, and ascorbic acid. Additionally, the glucose sensing mechanism is investigated through work function changes of the sensing electrode using a scanning Kelvin probe. Real-time sample testing has revealed that the sensor preserves the sensitivity in human saliva too. In summary, we conclude that the Ni-MOF/CP extended gate electrode EGFET is an alternative device for salivary glucose detection toward the noninvasive diagnosis of diabetes mellitus that can identify hyperglycemic, normal, and hypoglycemic conditions.