Water-soluble bioprobes with aggregation-induced emission characteristics for light-up sensing of heparin

Two water-soluble cationic fluorene-based fluorescent probes for heparin detection are designed and synthesized. A slight change in the molecular design results in two probes with opposite optical properties in their solution and aggregation states as well as a response to heparin in buffer solution. The probe with a propeller-like conformation exhibits aggregation-induced emission (AIE) characteristics and shows a green fluorescence enhancement upon interaction with heparin; in contrast, the probe with a more planar conformation has a fluorescence quenching response. A comprehensive study on heparin detection using the two probes was conducted, which revealed that the AIE probe shows a better performance than the aggregation-caused quenching (ACQ) probe in terms of sensitivity. The AIE probe integrated with graphene oxide (GO) further improves the heparin detection sensitivity and selectivity. The solution of AIE probe/GO emits strong green fluorescence only in the presence of heparin, which allows for light-up visual discrimination of heparin from its analogues such as chondroitin-4-sulfate and hyaluronic acid. Moreover, the linear light-up response of AIE probe/GO enables heparin quantification in the range of 0-13.2 μM with a detection limit of 10 nM, which is of practical importance for heparin monitoring during surgery or therapy.