After recombinant production, the engineered nanobody can be covalently modified in many ways in order to obtain its final desired format. For instance, nanobodies can be labeled with radioisotopes, small molecules (e.g. biotin) and fluorophores. A common modification site of a nanobody involves the C-terminal cysteine in which the sulfhydryl group reacts with a maleimide group under reducing conditions. We have experience with the chemical coupling of VHHs to single functional groups (e.g. maleimide-NOTA, maleimide-DOTA, and maleimide-Cy7) as well as with conjugations using bifunctional groups (e.g. maleimide-NOTA-myristic acid).
Based on your input, we are keen to explore different options for labeling and to create the optimal nanobody product that serves the application you have in mind.