Self-cleavable chemiluminescent probes suitable for protease sensing

A new generation of dioxetane-based chemiluminescent substrates suitable for detecting protease activities is described. Our strategy involves the use of a self-cleavable spacer as the key molecular component of these protease-sensitive chemiluminescent probes. Among the assayed strategies, the PABA (para-aminobenzylic alcohol) linker associated with an ether linkage enables the release of the light-emitting phenolic 1,2-dioxetane moiety through an enzyme-initiated domino reaction. To validate this strategy, two proteolytic enzymes were chosen: penicillin amidase and caspase-3, and the corresponding self-cleavable chemiluminescent substrates were synthesised. Their evaluation using an in vitro assay has enabled us to prove the decomposition of the linker under physiological conditions and the selectivity for the targeted enzyme.