Organic Electrochemical Transistors for the Detection of Xanthine

Abstract: Food waste is gradually becoming a serious global issue in recent decades. It is reported that more than 1.3 billion tonnes of food consisting of around 50 % meat products are wasted every year on a global scale, while there are more than 800 million of the global population who are starving at the same time. Therefore, a biosensor that can tell the freshness of food can be one of the solutions to reduce food waste, especially for fish, meat, and dairy products. Xanthine, a purine base derived from adenosine triphosphate (ATP), has been widely used as the analyte for detecting meat freshness. Xanthine is a common specie in all living organisms, but the death of a creature will lead to its accumulation of xanthine. So far, most sensing techniques for xanthine are designed based on traditional electrochemical biosensors. In this project, the sensing system is designed based on both an electrochemical platform and OECT. The OECT has a different working principle with respect to standard electrochemical setups and a huge potential to be used for several sensing applications. A p-type conjugated polymer is deposited on the devices by simple methods including drop casting and spin coating. During the project, the electrochemical biosensors were successfully produced and tested under four different conditions. The results show that PIBET-AO itself can exhibit sensing ability toward xanthine and, after adding the enzyme xanthine oxidase (XOD), the oxidation peak is shifted. Immobilization of XOD may allow the biosensor to work better at lower concentrations of xanthine. In addition to electrochemical biosensors, OECTs with PIBET-AO were fabricated and evaluated. The current result shows that the lowest concentration that can be measured is 50 − 100 µM. Since xanthine biosensor based on OECT has been rarely reported, more investigations should be performed to improve the sensing ability in the future.