Design,Sythesis And Application Study Of Reactive Organic Small Molecule Flurescent Probes

Over the past few decades,several techniques such as high performance liquid chromatography,capillary electrophoresis,fluorescence spectroscopy and electrochemistry have been applied to the detection of biologically active molecules.Among these techniques,fluorescence imaging techniques have been widely given attention due to its simple operation,high sensitivity,high spatial and temporal resolution,and non-invasive imaging properties.It is crucial to develop excellent probes for the imaging of active molecules produced in live cells.As the important reducing protein and gas signal molecule in organisms,respectively,both Nitroreductase(NTR)and Nitric oxide(NO)play a key role in a variety of physiological and pathological activities.Herein,fluorescence probe T-1 and T-2 are developed for the detection of NTR,and N-1 for NO detection.Research on its optical properties and cell imaging capabilities further confirmed the potential of the probes to image target molecules in biological systems.(1)In the passage,probes T-1 and T-2 were synthesized for the detection of NTR based on fused four-ring quinoxaline skeleton.In our previous study,a novel fused four-ring quinoxaline skeleton with high fluoresence quantum yield and excellent photo stability was firstly synthesized,indicating the potential application of the skeleton as a fluorophore in probes.In this paper,we introduced nitro groups at different position based on the skeleton.Probe T-1 and T-2 were developed based on the Intramolecular Charge Transfer(ICT)mechanism.Additionally,the quinoxaline part as highly ?-deficient aromatic heterocycles was used as the electron withdrawing part of the probe,and the nitro group was used as a fluorescence quenching group and the recognition group of NTR.Probes T-1 and T-2 show almost no fluorescence emission.In the presence of nicotinamide adenine dinucleotide(NADH),NTR catalyzes the reduction of the nitro group to produce the corresponding amino compounds F-1 and F-2,which stimulates the ICT effect from the amino group to the quinoxaline moiety.F-1 and F-2 exhibited significant fluorescence emission.When NADH existed,the peak fluorescence intensity was increased sharply and can reach the plateau within 20 min after addition of NTR.The probe also shows a significant fluorescence turn-on response,good selectivity and high sensitivity(Detection of limit < 58 ng/m L).In addition,probes T-1 and T-2 also showed good biocompatibility,indicating that probes T-1 and T-2 can become effective tools for monitoring NTR in biological systems.(2)Probe N-1 was synthesized based on a novel benzoindole skeleton.We select hemicyanine dye G-1 as the fluorophore,ester group as the linking group and o-phenylenediamine(OPD)as the NO recognition group in the probe.The probe is designed with the PET mechanism and shows 7-fold fluorescence decrease toward NO.As the addition of DEA·NONOate(NO donor),the fluorescence intensity at 487 nm gradually decreased and reached a plateau within 12 min.In addition,probe N-1 also has the advantage of high sensitivity(detection of limit < 20 n M)and strong specificity.Due to its excellent membrane permeability and good biocompatibility,probe N-1 has been successfully used to NO bioimaging in Hela cells.