Q-Bodies from Recombinant Single-Chain Fv Fragment with Better Yield and Expanded Palette of Fluorophores

Fluorescence-based immunosensors serve a vital role in biotechnology and diagnostic and therapeutic applications. Our group recently developed a unique fluoroimmunosensor named Quenchbody (Q-body) that operates based on the principle of quenching and the antigen-dependent release of fluorophore, which is incorporated to a recombinant antibody fragment, either the single-chain Fv (scFv) or the Fab fragment of an antibody, using a cell-free transcription-translation system. With the objective of extending the functionality and diversity of the Q-body, here we attempted to make Q-bodies by labeling the recombinant scFv, which was prepared from. E. coli using several commercially available dye-maleimides. As a result, we reproducibly obtained larger amounts of antiosteocalcin Q-bodies, with an improved yield and cost-efficiency compared with those obtained from a conventional cell-free system. The fluorescence intensity of each Q-body, including that labeled with newly tested rhodamine red, was significantly increased in the presence of an antigen with a low detection limit, although some differences in response were observed for the dye with different spacer lengths between dye and maleimide. The results indicate the Q-body's applicability as a powerful multicolored sensor, with a potential to simultaneously monitor multiple targets in a sample.