Monitoring supported lipid bilayers with n-type organic electrochemical transistors

Supported lipid bilayers (SLBs) have emerged as powerful model systems to study various membrane-governed cellular events. Conducting polymers are excellent materials to establish electrical communication with SLBs. However, forming SLBs that are defect-free on the existing library of electronic polymer films, which have not been designed to interface lipids, remains a challenge. Moreover, the existing polymers are predominantly p-type conductors, hindering the development of devices that can be superior to current technologies. In this work, we synthesized an n-type semiconducting polymer based on a naphthalene 1,4,5,8 tetracarboxylic diimide bithiophene (NDI-T2) backbone functionalized with bio-inspired, lysine-based side chains (L2). The lysine chains, that are oriented on the surface of the film, facilitated the assembly of the zwitterionic lipid vesicles into an SLB. The n-type polymer also proved to be an ideal channel material for the state-of-the-art bioelectronic transducer, i.e., organic electrochemical transistor (OECT). We used the n-type, accumulation mode OECTs to assess the quality of the SLB as well as to monitor the activity of a pore forming protein integrated into the SLB. Our work marks the first demonstration of a bio-functionalized n-type polymer, specifically designed for interfacing the lipid membrane, alongside the high operational stability in biologically relevant electrolytes and sufficient performance in microscale transistors for biosensing applications.