Fluorescence turn-on detection of live cell apoptosis using a hyperbranched conjugated polyelectrolyte

Abstract

A fluorescence “turn-on” assay for live cell apoptosis imaging is developed based on self-assembled complexes between a cationic water-soluble hyperbranched conjugated polyelectrolyte (HCPE) and an Asp-Glu-Val-Asp (DEVD) peptide substrate labelled with a fluorescence quencher (DEVD-dabcyl). The polymer fluorescence can be significantly quenched upon DEVD-dabcyl binding, and the fluorescence is switched on upon treatment of the complexes with caspase-3/7, which are activated in the cell apoptotic process and are able to cleave the DEVD moiety. The light-up nature of the assay allows monitoring of caspase-3/7 activities both in solutions and in living cells with a high signal to noise ratio, which provides a new opportunity to screen caspase inhibitors and detect cell apoptosis.