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Metabolites are essential molecules involved in various metabolic processes, and their deficiencies and excessive concentrations can trigger significant physiological consequences. The detection of multiple metabolites within a non‐invasively collected biofluid could facilitate early prognosis and diagnosis of severe diseases. Here, a metal oxide heterojunction transistor (HJ‐TFT) sensor is developed for the label‐free, rapid detection of uric acid (UA) and 25(OH)Vitamin‐D3 (Vit‐D3) in human saliva. The HJ‐TFTs utilize a solution‐processed In2O3/ZnO channel functionalized with uricase enzyme and Vit‐D3 antibody for the selective detection of UA and Vit‐D3, respectively. The ultra‐thin tri‐channel architecture facilitates strong coupling between the electrons transported along the buried In2O3/ZnO heterointerface and the electrostatic perturbations caused by the interactions between the surface‐immobilized bioreceptors and target analytes. The biosensors can detect a wide range of concentrations of UA (from 500 nm to 1000 µM) and Vit‐D3 (from 100 pM to 120 nm) in human saliva within 60 s. Moreover, the biosensors exhibit good linearity with the physiological concentration of metabolites and limit of detections of ≈152 nm for UA and ≈7 pM for Vit‐D3 in real saliva. The specificity is demonstrated against various interfering species, including other metabolites and proteins found in saliva, further showcasing its capabilities. [ABSTRACT FROM AUTHOR]

Transistor-based biosensors represent an emerging technology for inexpensive point-of-care testing (POCT) applications. However, the limited sensitivity of the current transistor technologies hinders their practical deployment. In this study, we developed tri-channel In 2 O 3 /ZnO heterojunction thin-film transistors (TFTs) featuring the surface-immobilized enzyme glucose oxidase to detect glucose in various biofluids. This unusual channel design facilitates strong coupling between the electrons transported along the buried In 2 O 3 /ZnO heterointerface and the electrostatic perturbations caused by the interactions between glucose and surface-immobilized glucose oxidase. The enzyme selectively binds to glucose, causing a change in charge density on the channel surface. By exploring this effect, the solid-state biosensing TFT (BioTFT) can selectively detect glucose in artificial and real saliva over a wide range of concentrations from 500 nM to 20 mM with limits of detection of ∼365 pM (artificial saliva) and ∼416 nM (real saliva) in less than 60 s. The specificity of the sensor towards glucose has been demonstrated against various interfering species in artificial saliva, further highlighting its unique capabilities. Moreover, the BioTFTs exhibited good operating stability upon storage for up to two weeks, with relative standard deviation (RSD) values ranging from 2.36% to 6.39% for 500 nM glucose concentration. Our BioTFTs are easy to manufacture with reliable operation, making them ideal for non-invasive POCT applications. • We developed a solid-state thin-film transistors-based biosensor (BioTFT) for the noninvasive and rapid detection of glucose. • High-sensitive BioTFT is fabricated using a tri-channel In2O3/ZnO heterointerface via solution-processing of the active materials. • The BioTFTs can detect glucose in artificial and real saliva over a wide range of concentrations (500 nM–20 mM) in under 60 s. • The BioTFT can detect selectively ultralow glucose concentrations in non-invasive biofluids, such as human saliva, with a low limit of detection (LOD) of 365 pM. • The proposed technology could be adapted for rapid, non-invasive detection of multiple analytes in human saliva. [ABSTRACT FROM AUTHOR]