Figure 1.

The biosensing principles of the constructs listed in Table 1 are summarized here as split in two groups. In a), the sensing principles underlying cleavable platforms are presented in which simple hydrolysis of protease target site-bearing hybrid proteins by an effector protease (P) result in a macroscopic signal. Among others, variations of the migration pattern, enzyme activation or inactivation, repressor inactivation, enhanced fluorescence by removal of a quencher or dual fluorescence emission by FRET modulation. In b), a ligand (L) promotes conformational modifications in the sensor either multimerization, correct folding or allosteric activation. A few enzyme biosensors are inactivated in presence of the ligand probably by steric hindrance of the active site.