A water soluble cationic fluorescent probe (TPEDPyMe) was designed and synthesized by attaching two pyridinium moieties onto the tetraphenylethene(TPE) core.The molecular structure of TPEDPyMe was characterized by multiple spectroscopic techniques

and its fluorescence property was examined.As its maternal compound

TPEDPyMe exhibited typical aggregation-induced emission (AIE) behavior

and the emission peaked at around 630 nm in aqueous solution.TPEDPyMe was used as a fluorescent probe to detect ctDNA in tris-HCl buffer solution at a pH value of 7.2. It was found that the fluorescence intensity of the TPEDPyMe in the buffer solution was boosted up to 20 folds when the concentration of ctDNA increased from 0 g/mL to 500 g/mL.Meanwhile

the emission peaks blue-shifted from 627 nm to 576 nm.In the concentration region from 0 g/mL to 50 g/mL

the change in fluorescence intensity was linearly proportional to the concentration of ctDNA.In this region

the Stern-Volmer constant or KSV was calculated to be 1.4 102

showing a desirable sensitivity of TPEDPyMe to ctDNA.Moreover

when the concentration of ctDNA increased from 0 g/mL to 500 g/mL

the emission peak shifted from 633 nm to 578 nm.This phenomenon implies that the TPEDPyMe can be used as a dual-responsive fluorescent label for probing ctDNA

which is of great significance in biosensor technologies.In summary

the present results indicate that TPEDPyMe is a promising fluorescent probe for the detection of DNA species and more detailed investigation is going on in the laboratory.