Development of Ligand Assay Systems Using Semisynthetic Biosensors Based on Protein

A variety of biological substances and events in cells can be precisely detected and monitored in real time using chemically fabricated biosensors composed of an artificial small molecule and a protein scaffold. In the past, these protein-based semisynthetic biosensors were synthesized in a laboratory and subsequently injected into the cells by means of invasive approaches. Recent advances made in bioorthogonal protein conjugation techniques, as well as covalent, and non-covalent methods for the synthesis of DNA–protein conjugation, now make it possible to design and develop semisynthetic biosensors directly within living cells, opening up new avenues for the advancement of biomedical research. This chapter discusses biosensors based on proteins for targeting subcellular components and site-specific modification using genetically engineered reactive handles. In addition, this chapter focuses on affinity-based semisynthetic biosensors and the characteristics of ligand-directed chemistry, with a particular emphasis on the labelling of native proteins by means of ligand-directed tosyl chemistry. Furthermore, non-covalent protein labelling for the fabrication of protein-based semisynthetic biosensors has been reviewed. Finally, the synthesis of protein–DNA conjugates and their applications in biosensing has been described in detail.