Design,Synthesis And Sensing Properties Of Fluorescent Probe Based On Diketopyrrolopyrrole-1,3 Indanedione

Fluorescent probes based on small molecules have received considerable attention in biosensing and chemical sensing. Diketopyrrolopyrrole, which owns excellent property, has received considerable attention as biosensors in literatures. Therefore, we focused on how to design such DPP fluorescet probe, which contains simple structures, high efficiency and sensitivity during the sensing process. The research ideas as follows:(1) Probe DPP1 is synthesized by condensation reaction between DPP1 and 1,3-indanedione, and Michael addition site is introduced Michael addition site.(2) Due to the strong electrophilic effct by DPP unit and 1,3-indanedione fragment, Michael addition reactivity of DPP1 will be enhanced,and the sensitivity between DPP1 and targets will be improved greatly.(3) CN- reacts with double bonds in DPP1 through Michael addition. After that, 1,3-indanedione fragment and DPP core will fold in a sandwich-like mode. Therefore, the sensing mechanism for CN- detection is based on Exciplex formation.(4) Cysteine(Cys) reacts with double bonds in DPP1 rapidly, and then the π framework is reduced. The electrophilic effct produced by 1,3-indanedione fragment is removed. Therefore, the sensing mechanism for Cys detection is based on ICT. A new fluorescent probe DPP1 comprising diketopyrrolopyrrole and 1,3-indanedione-based Michael receptor, which recognizes cyanide anion and Cys respectively, with high selectivity is designed and synthesized. In this work, the photophysical properties of the probe DPP1 and the sensing process(for Cys and CN-) are studied, such as UV-vis absorption, fluorescence emission and 1H NMR titration. When DPP1 reacts with CN- and Cys in solution respectively, the colors of solution change from purple to yellow and orange respectively, which suggests that naked-eye selective detection of them becomes possible. Meanwhile, fluorescent labeling of protein BSA(bovine serum albumin) and adult skin fibroblast cells imaging are studied. In conclusion, DPP1 is a colorimetric and ratiometric fluorescent probe toward CN-, with high selectivity and sensitivity. The absorption peaks of DPP1 at 359 and 553 nm gradually decrease following the formation of one new band centered at 480 nm. The emission peaks of DPP1 at 485 nm and 572 nm increase, due to the formation of Exciplex formation. The detection limit for CN- is 0.36 μM, which is far lower than the WHO guideline of 1.9 μM. At the same time, DPP1 is also a wonderful probe for Cys detection; especially the reaction time is less than 2 minutes. The absorption peaks of DPP1 at 359 and 553 nm gradually decrease following the formation of one new band centered at 484 nm. The emission peak of DPP1 at 485 nm increases, the emission peak of DPP1 at 667 nm keeps stable. The detection limit for Cys is 1.21 μM. Besides, DPP1 shows excellent performance during the fluorescent labeling BSA process, such as high selectivity and short response time(5 minutes), these results are in accordance with the observations in the case of Cys. Subsequently, DPP1 has a very low cytotoxicity and good biocompatibility in cell imaging, and the cell imaging test shows that DPP1 accumulates in the cytoplasm. These results give DPP1 as a biosensor a promising future in the applications.