## 2 Organic Electrochemical Transistors (OECTs)
In chemical sensors, the measurement of chemical information within a system (such as analyte concentration) involves correlating a physical property with an analytically useful signal (e.g., absorbance). On the other hand, biological sensors detect analytes of biological origin, including enzymes, antibodies, DNA, proteins, and microorganisms [28]. Recent OECTs are more focused on the last ones. OECT devices exhibit promising capabilities in translating minor fluctuations in ion concentration into substantial variations in electrical current, a feature highly advantageous for bioelectronics applications. These devices are gradually finding their place as integral components in logic circuitry and flexible devices in computing. However, for this technology to transcend scientific interest and become viable for future portable and wearable applications, it must meet certain criteria, including lightweight and flexibility, stability under normal operating conditions, low-power consumption, and continuous recording capabilities. Bioelectronics, the most remarkable application of OECTs, has experienced a significant surge in research funding in recent years [29; 30]. Presently, it encompasses a wide spectrum of applications ranging from medical devices to sensors designed for environmental monitoring. In the realm of medical devices, many patients have witnessed enhancements in their quality of life attributable to innovations like cardiac pacemakers, cochlear and retinal implants, and glucose sensors. As bioelectronics becomes increasingly integrated into our daily lives, it has garnered considerable attention from the media, driven both by speculative portrayals in science fiction and by real-world research breakthroughs. The growing interest in OECT development is evident, with several examples emerging in 2024. For instance, [PERSON] et al. addressed the challenge of accurately detecting trace levels of glycoproteins in biofluids--a capability often missing in portable point-of-care (POC) diagnostic devices--by creating a compact, highly sensitive bioelectrochemical patch utilizing boronate-affinity amplified organic electrochemical transistors (BAAOECTs). This innovative device takes advantage of the cascading signal enhancement from boronate-affinity, which targets multiple glycoprotein regions, combined with the signal amplification properties of OECTs. As a result, the BAAOECTs achieved an outstanding detection limit of 300 aM within 25 min, offering approximately three orders of magnitude greater sensitivity than commercial electrochemical luminescence (ECL) kits [31]. The system also integrates a microfluidic chip, a microcontroller module, and a wireless sensing network, automating the testing process and making it feasible to operate in resource-limited settings. The effectiveness of this portable biosensing platform has been confirmed through clinical diagnostic applications, particularly for heart failure. Overall, the significant sensitivity improvements and automated workflow of the BAAOECTs biosensing system demonstrate a promising, scalable approach to advancing POC diagnostic capabilities for glycoproteins. In addition, [PERSON] et al. described selenophene n-type polymers as glucose sensors. Furthermore, with a remarkably low detection limit of 10 nMm and decent selectivity, it is further implemented [32]. Research has shown that incrementally augmenting the amount of selenophene integrated into polymer structures can result in decreased levels of the lowest unoccupied molecular orbitals, enhanced properties related to charge transport, and better capabilities for ion absorption simultaneously, and improving the capacity of the OECTs.