Bioelectronics represents an interdisciplinary field merging biology with electronics with the focus on developing devices that interact with biological systems. Therefore, bioelectronics can help us to understand and utilize biological processes with electronic means. This can aid in the progression of healthcare such as improved diagnostic tools, innovative therapy, or personalized medicine. Interfacing biology and electronics presents significant challenges in material science, necessitating the continuous exploration of new materials and measurement systems that meet both electronic and biological requirements. Organic mixed ionic-electronic conductive polymers are one material class that has gained great interest due to, as the name suggests, their dual ionic and electronic properties. Furthermore, these polymers have shown greatly adaptability at interfacing with biology, often superior to traditional materials as has been observed in neural probes. This curious interplay of ions and electrons in these polymers is harnessed by organic electrochemical transistors (OECTs), which transduce biological signals into electrical ones. OECTs are used to amplify measured electric signals or when functionalized with specific biorecognition elements to detect analytes. Given the operation principle of OECTs within aqueous environments, a variety of (bio-)sensors can be realized to interact with biological processes based on capacitive or faradaic currents. An adaptable sensor platform that can be used as a point-of-care device is highly sought after, as for example glucose sensors. In general, biosensors and their point-of-care applications play an important role in society for diagnostics, as evidenced by the COVID-19 pandemic, and for personalized medicine.

This work explores various aspects of OECT biosensors, including capacitive sensors with aptamers, enzymatic sensing, and enzymatically polymerized OECTs. OECTs are integrated with recognition elements on different surfaces to measure biomarkers for inflammation, and enzymes are incorporated into ad-hoc formed glucose sensor. The first works employ a classical layer-by-layer technique, clearly delineating the interaction sites. Later investigations utilize the small size of electro-polymerizable monomers to achieve conformability between enzymes and polymers, resulting in seamless, interconnected bioelectronic devices. Furthermore, biological processes can be utilized in the fabrication of enzymatically formed OECTs. Lastly OECTs formed by enzymatic polymerization exhibit high electrical stability with bio-integrability. These studies highlight various facets of OECTs and their interactions with biological entities, underscoring their potential in advancing bioelectronic applications.