Enhanced BSA Detection Precision: Leveraging High-Performance Dual-Gate Ion-Sensitive Field-Effect-Transistor Scheme and Surface-Treated Sensing Membranes

Bovine serum albumin (BSA) is commonly incorporated in vaccines to improve stability. However, owing to potential allergic reactions in humans, the World Health Organization (WHO) mandates strict adherence to a BSA limit (≤50 ng/vaccine). BSA detection with conventional techniques is time-consuming and requires specialized equipment. Efficient alternatives such as the ion-sensitive field-effect transistor (ISFET), despite rapid detection, affordability, and portability, do not detect BSA at low concentrations because of inherent sensitivity limitations. This study proposes a silicon-on-insulator (SOI) substrate-based dual-gate (DG) ISFET platform to overcome these limitations. The capacitive coupling DG structure significantly enhances sensitivity without requiring external circuits, owing to its inherent amplification effect. The extended-gate (EG) structure separates the transducer unit for electrical signal processing from the sensing unit for biological detection, preventing chemical damage to the transducer, accommodating a variety of biological analytes, and affording easy replaceability. Vapor-phase surface treatment with (3-Aminopropyl) triethoxysilane (APTES) and the incorporation of a SnO2 sensing membrane ensure high BSA detection efficiency and sensitivity (144.19 mV/log [BSA]). This DG-FET-based biosensor possesses a simple structure and detects BSA at low concentrations rapidly. Envisioned as an effective on-site diagnostic tool for various analytes including BSA, this platform addresses prior limitations in biosensing and shows promise for practical applications.

Development of Tungsten Oxide Nanoparticle Modified Carbon Fibre Cloth as Flexible pH Sensor

A reagent-less pH sensor based on disposable and low cost carbon fibre cloth (CFC) is demonstrated for the first time, where tungsten oxide nanoparticles were grown directly onto the CFC substrate. For comparison purpose, tungsten oxide nanoparticle modified glassy carbon electrode (GCE) was also fabricated as a pH sensor, where hydrothermally synthesized tungsten oxide nanoparticles were drop casted onto the GCE surface. The corresponding equilibrium potential using tungsten oxide/CFC as a pH sensor was measured using open circuit potential (OCP), and was found to be linear over the pH range of 3-10, with a sensitivity of 41.38 mVpH^-1, and response time of 150 s. In the case of tungsten oxide/GCE as a pH sensor, square wave voltammetry (SWV) was used to measure the shifts in peak potential and was found to be linear with a pH range of 3-11, and a sensitivity of 60 mVpH^-1 with a potential drift of 2.4-5.0% after 3 hour of continuous use. The advantages of tungsten oxide/CFC and tungsten oxide/GCE as pH sensing electrode have been directly compared with the commercial glass probe based electrode, and validated in real un-buffered samples. Thereby, tungsten oxide nanoparticles with good sensitivity and long term stability could be potentially implemented as a low cost and robust pH sensor in numerous applications for the Internet of Things (IoT).

Effects of UV-Ozone Treatment on Sensing Behaviours of EGFETs with Al₂O₃ Sensing Film

The effects of UV-ozone (UVO) treatment on the sensing behaviours of extended-gate field-effect transistors (EGFETs) that use Al₂O₃ as the sensing film have been investigated. The Al₂O₃ sensing films are UVO-treated with various duration times and the corresponding EGFET sensing behaviours, such as sensitivity, hysteresis, and long-term stability, are electrically evaluated under various measurement conditions. Physical analysis is also performed to characterize the surface conditions of the UVO-treated sensing films using X-ray photoelectron spectroscopy and atomic force microscopy. It is found that UVO treatment effectively reduces the buried sites in the Al₂O₃ sensing film and subsequently results in reduced hysteresis and improved long-term stability of EGFET. Meanwhile, the observed slightly smoother Al₂O₃ film surface post UVO treatment corresponds to decreased surface sites and slightly reduced pH sensitivity of the Al₂O₃ film. The sensitivity degradation is found to be monotonically correlated with the UVO treatment time. A treatment time of 10 min is found to yield an excellent performance trade-off: clearly improved long-term stability and reduced hysteresis at the cost of negligible sensitivity reduction. These results suggest that UVO treatment is a simple and facile method to improve the overall sensing performance of the EGFETs with an Al₂O₃ sensing film.

WO3 nanoparticle-based conformable pH sensor

pH is a vital physiological parameter that can be used for disease diagnosis and treatment as well as in monitoring other biological processes. Metal/metal oxide based pH sensors have several advantages regarding their reliability, miniaturization, and cost-effectiveness, which are critical characteristics for in vivo applications. In this work, WO3 nanoparticles were electrodeposited on flexible substrates over metal electrodes with a sensing area of 1 mm(2). These sensors show a sensitivity of -56.7 ± 1.3 mV/pH, in a wide pH range of 9 to 5. A proof of concept is also demonstrated using a flexible reference electrode in solid electrolyte with a curved surface. A good balance between the performance parameters (sensitivity), the production costs, and simplicity of the sensors was accomplished, as required for wearable biomedical devices.