Design,Synthesis And Properties Of Novel NO And GSH Fluorescent Probes

Fluorescent probes have the advantages of simple operation,high sensitivity,and rapid real-time,which can realize non-invasive monitoring of various biomolecules in cells and in vivo.For example,two-photon fluorescent probes can be used to monitor the dynamic changes of biomolecules in cells and biological tissues over a long period of time due to their advantages such as less photodamage,low background fluorescence,and strong tissue penetration.Near-infrared fluorescent probes also show great potential in early tumor diagnosis,drug delivery,and intraoperative navigation.Compared with nanoprobes,small-molecule fluorescent probes based on organic dyes have unique advantages,such as well-defined metabolic pathways and good tissue permeability.However,traditional small molecule fluorescent probes suffer from solvatochromism fluorescence quenching and limited selectivity.In response to the above problems,a two-photon NO fluorescent probe with anti-solvatochromism and a highly specific nearinfrared GSH(glutathione)fluorescent probe were designed and developed in this paper,which were successfully applied to the imaging detection of cells and related analytes in vivo.The details are as follows:First,most of the existing D-A(Donor-Acceptor)type two-photon fluorescent probes are prone to intramolecular charge transfer in strong polar solvents,resulting in fluorescence quenching(called solvatochromism),which inevitably affects their applications in living organisms.To address this problem,we linked the recognition group to a hydrogen-bond-induced fluorescence-enhanced dye to construct a twophoton fluorescent probe with anti-solvatochromism.Compared with traditional fluorescent probes,anti-solvatochromic fluorescent probes show significant fluorescence enhancement in strong polar solvents,and have the advantages of good water solubility,high selectivity,and large two-photon absorption cross-section,and have been successfully used to detect the dynamic changes of NO in living cells and tumor tissues.Second,because GSH,Cys(Cysteine),and Hcy(Homocysteine)are similar in molecular framework and reactivity,it is difficult for many probes to specifically recognize GSH in three similar thiols.In response to this problem,we designed a novel probe-responsive site that specifically recognizes GSH based on halogen nucleophilic substitution and intramolecular self-elimination,and constructed a series of probes.Through spectral testing and selective screening,we identified compounds 3-7 as the best probes for GSH detection.This probe has the advantage of good selectivity and has been successfully applied to monitor the dynamic changes of GSH content in different cells.Third,on the basis of the above work,we synthesized near-infrared GSH fluorescent probes 4-3 by using near-infrared Huda dye as a fluorophore to connect with the selected GSH recognition sites.The probe selectively detects GSH in both buffer solution and cells,and can be slowly activated by high concentrations of GSH in tumors.Based on this feature,we further covalently linked the recognition site to antitumor drugs to synthesize GSH-activated prodrug molecules P-CA4.Experiments have confirmed that prodrug molecules P-CA4 can slowly release tumor drugs by reacting with GSH in cancer cells,so as to achieve the purpose of killing cancer cells.