Tetrazine-trans-cyclooctene Mediated Conjugation of Antibodies to Microtubules Facilitates Subpicomolar Protein Detection.

Engineering cargo-loading strategies is crucial to developing nanotechnological applications of microtubule-based biomolecular transport systems. Here, we report a highly efficient and robust bioconjugation scheme to load antibodies to microtubules. Our method takes advantage of the inverse-electron-demand Diels-Alder addition reaction between tetrazine and trans-cyclooctene: the fastest known bioorthogonal reaction, characterized by its excellent selectivity and biocompatibility. As proof of concept, we performed kinesin-1 gliding motility assays with antibody-conjugated microtubules and demonstrated the highly sensitive detection of fluorescent protein analyte down to 0.1 pM in microliter sample volumes. Importantly, the detection selectivity was retained in the presence of other fluorescent background proteins. We envision the applicability of our fast, simple, and robust conjugation method to a wide range of biosensing platforms based on biomolecular transport systems.