Conjugated polyelectrolyte as signal amplifier for fluorogenic probe based enzyme activity study

A cationic conjugated polyelectrolyte (CPE) is used as a signal amplifier to enhance the sensory response of a fluorogenic substrate (fluorescein diacetate) for esterase activity study. As fluorescein diacetate is nonfluorescent, it can be cleaved by esterase to yield a negatively charged fluorescent dye. Electrostatic interaction between the cationic CPE and negatively charged fluorescent dye leads to complexes which allow fluorescence resonance energy transfer to amplify the dye signal by a factor of up to ∼19-fold. The presence of CPE does not obviously influence the enzyme efficiency and the assay allows real-time monitoring of enzyme activity. As compared with common fluorogenic assays, the CPE amplified system has the advantage of shorter readout time with higher sensitivity, which could have wide applications in high throughput screening of enzyme activity.