Significantly different fluorescent responses of two aggregation-induced emission probes to heparin

Heparin (Hep) is a widely used clinical anticoagulant which requires regular detection to avoid hemorrhage complication. Herein, we found that Hep could be quantitatively determined by both the four-armed (TPE-4Py) and three-armed (TPA-3Py) cationic water-soluble, aggregation-induced emission (AIE) luminogens. TPE-4Py and TPA-3Py could quantify 5.95 ng/mL to 1.996 mg/L, and 49.53 ng/mL to 6.14 mg/L Hep, with the quan-tum yield of 25.94% and 7.81%, respectively. In addition, the two probes showed many different fluorescent responses to Hep such as opposite fluorescence spectral shift with increased Hep, and opposite circular dichroism spectra, etc. Finally, the fluorescence emitted by the TPE-4Py binding to sulfate-removed Hep is stronger than that emitted by the TPE-4Py binding to Hep. According to the simulation results, it was probably because that in Hep the third sulfonic group competes with the other two sulfonic groups, thus weakening its binding ability with the two methylated vinylpyridine groups in TPE-4Py. Those demonstrate that small structural changes of the dyes can impact on the binding preference of Hep. On the other hand, the sulfonic group in Hep can take the unexpected way to affect on its binding ability with TEP-4Py. This study helps us to understand the binding preference of Hep with AIE probes and adds important knowledge on Hep interaction with different cationic molecules which could be practically useful for drug development in which Hep is involved.