Polycation-induced benzoperylene probe excimer formation and the ratiometric detection of heparin and heparinase

A benzoperylene probe excimer emission in an aqueous buffer solution is observed for the first time, and a novel ratiometric fluorescence method based on the probe excimer emission for the sensitive detection of heparin and heparinase is demonstrated. A negatively charged benzoperylene derivative, 6-(benzo[ghi]perylene-1,2-dicarboxylic imide-yl)hexanoic acid (BPDI), was employed. A polycation, poly(diallyldimethylammonium) chloride (poly-DDA), could induce aggregation of BPDI through noncovalent interactions. A decrease of BPDI monomer emission and a simultaneous increase of BPDI excimer emission were observed. Upon the addition of heparin, the strong binding between heparin and poly-DDA caused release of BPDI monomer molecules, and an excimer-monomer emission signal transition was detected. However, after the enzymatic hydrolysis of heparin by heparinase, heparin was hydrolyzed into small fragments, which weakened the competitive binding of heparin to poly-DDA. Poly-DDA induced aggregation of BPDI, and a monomer-excimer emission signal transition was detected. Our assay is simple, rapid, inexpensive, sensitive and selective, which could facilitate the heparin and heparinase related biochemical and biomedical research.