Flexible organic electrochemical transistors for bioelectronics

Abstract

Organic electrochemical transistors (OECTs) have been shown to be a promising platform for the development of highly flexible, sensitive, and stable biosensors in bioelectronics and wearable electronics, as well as for the implementation of artificial neuromorphic electronics. Biosensors based on OECTs operate through a combination of signal transduction and amplification when specific biological events occur. In this thesis, we present three applications of OECT-based biosensors for non-invasive glucose analysis, rapid detection of SARS-CoV-2 variants, and sweat lactate monitoring. Firstly, we propose a solution to address the lack of reliable non-invasive biosensors for blood glucose monitoring by using highly sensitive and ultrasensitive saliva glucose sensors based on OECTs. These sensors can perform real-time monitoring of glucose levels in unstimulated mixed saliva samples using a portable meter and mobile smartphone. Clinical trials involving both diabetic and healthy human subjects demonstrate a strong correlation between the fasting glucose levels in saliva and blood, with a deviation of approximately 10% that is independent of gender, age, and diabetic condition. This approach provides a promising pathway for clinically non-invasive and continuous glucose monitoring. Secondly, we developed an ultra-sensitive multi-gate OECT-based biosensor for the rapid detection of different variants of SARS-CoV-2 nucleic acid with excellent selectivity. Five dominant VOCs (Alpha, Beta, Gamma, Delta, and Omicron) and, original SARS-CoV-2 virus were synchronously tested with an ultralow detection limit of 1 x 10-17M in human saliva/serum within 15 mins. This approach shows promise for use in point-of-care self-health monitoring of SARS-CoV-2 variants and allows for the diagnosis of any known mutated COVID-19 virus. Lastly, we addressed the challenge of fitting the adaptive subnanometre interlayer spacing (d) into various sizes of guest molecules by incorporating positively charged polymer chains into GO membranes. This approach allowed for the stable and well-controlled nanocapillaries to sieve small molecules, e.g., salts and biomarkers, with a rejection beyond 99.9%. We coupled the molecule-sieving membranes with OECTs and achieved rapid detection of lactate and uric acid at high accuracy. Based on this finding, we demonstrated a user-friendly sweat lactate rapid test kit, which detected sweat lactate secreted from the human body within a few minutes. These results highlight the potential of OECT-based biosensors in various fields, including healthcare and environmental monitoring. In summary, we highlight the potential of OECT-based biosensors for various applications, including healthcare and disease monitoring. These innovative OECT-based biosensors offer a flexible, sensitive, and stable platform that could revolutionize the field of biosensors.