Principal Investigator: Prof. Sahika Inal and Prof. Stefan Arold

Poster Presenter: Raik Gruenberg

Lab: StruBE; Organic Bioelectronics Lab

High Density Nanobody Surfaces for Bioelectronic Protein Sensing




The performance of biosensor devices depends critically on the density, orientation and stability of the biological receptor. Traditional approaches rely on random adsorption or chemical immobilization of antibodies. This necessarily leads to a variable fraction of binding-incompetent receptors with often compromised stability and lifetime. We here introduce the SpyDirect biofunctionalization method that creates an ultra-high-density array of correctly oriented nanobody receptors which are stably linked to the gate electrode of an organic electrochemical transistor (OECT). The method builds on cysteine-terminated spyTag peptides to which nanobody-spyCatcher fusion proteins are autocatalytically attached. Our structure-guided design allowed nanobody packing up to the physical limit of 7.8 × 10^12 protein molecules per cm2 and featured ~70% binding capacity for SARS-CoV-2 Spike S1 subunit proteins (likely again limited by physical packing). When combined with our rapid and highly sensitive OECT immunosensor platform [1], the new SpyDirect functionalization improved long-term stability, and lowered the background noise from complex media, such as saliva and unprocessed wastewater. Moreover, SpyDirect functionalization was faster, easier, and did not require organic solvents. Therefore, SpyDirect is a broadly applicable biofunctionalization method for improved biosensor performance. [1] Guo et al. (2021) Rapid single-molecule detection of COVID-19 and MERS antigens via nanobody-functionalized organic electrochemical transistors. Nat. Biomed. Eng. 5, 666-677