Research On Optical Imaging Probes For Bioactive Small Molecules

Bioactive small molecules such as reactive oxygen species,biothiols and reactive carbonyl species are involved in many physiological functions in the body and closely associated with a serious of pathological events.Therefore,rapid,real-time and accurate detection of bioactive small molecules is crucial for medical diagnosis,pharmaceutical research and development,as well as in-depth elucidation of the physiological and pathological processes of the diseases.Optical imaging probes are popular due to their advantages including minimal invasiveness,high sensitivity and high spatial resolution and so on.Thus,it is an important research field to develop specific optical imaging probes with excellent performance activated by bioactive small molecules.Based on the design and recognition mechanism of molecular probe,this thesis will focus on the development of bioactive small molecules responsive fluorescent and chemiluminescent probes,as well as perform their further biological applications.Methylglyoxal(MGO)plays an important role in diabetes and its corresponding complications.A 1,8-naphthalimide-based two-photon fluorescent probe termed NI-OPD was designed based on the photoinduced electron transfer(PET),in which o-phenylendiamine serves as the MGO recognition unit and methyl sulphonamide serves as the endoplasmic reticulum(ER)-targeting group.After the reaction with MGO,the PET effect in NI-OPD was inhibited,exhibiting the "Turn-ON" fluorescent signal.NI-OPD can detect MGO with high sensitivity and selectivity,and was used to monitor changes in the exogenous and endogenous MGO levels under ER stress conditions.Accordingly,the probe was successfully used for two-photon fluorescent imaging and detection of MGO levels in different organs in diabetic mouse model.Cysteine(Cys)and homocysteine(Hcy)are essential for maintaining the cellular redox homeostasis.By incorporating labile 4-methlythiophenol into the pyronin fluorophore,a ratiometric fluorescent probe,PYR,was constructed for the response of Cys/Hcy.The fluorescence emission wavelength of PYR is at 620 nm(red fluorescence)and bule-shifts to 540 nm upon addition of Cys or Hcy.And the fluorescence intensity ratio shows a well linear relationship with the concentration of Cys/Hcy.The probe displays a selectively marked signals change in red-to-green fluorescence emission(F540 nm/F620 nm)and absorption intensity ratio(A455 nm/A580 nm)upon detecting Cys/Hcy with high selectivity and sensitivity.PYR possesses good biocompatibility and was successfully used for visualizing Cys/Hcy in MCF-7 cells under H2O2-induced redox imbalance conditions,mouse kidney tissue and D.magna model.Singlet oxygen(1O2)plays a vital role in metabolism and tumor photodynamic therapy(PDT).By caging the precursor of phenoxy-dioxetane scaffolds and a dicyanomethylchromone acceptor,a near-infrared(NIR)chemiluminescent probe(CL-SO)was constructed for selective 1O2 detection.In the presence of 1O2,CL-SO was oxidized to phenol-dioxetane species followed by spontaneous decomposition through chemiexcitation and accompanied by the release of NIR chemiluminescence signals(700 nm).Compared with traditional 1O2 fluorescent probe(SOSG)and chemiluminescent probe(MVP),CL-SO showed higher signal-to-noise ratio(1011-fold enhancement in signal intensity)and chemiluminescence intensity.CL-SO possesses good biocompatibility and was applied to image 1O2 in living cells and the abdominal cavity of the mouse.Importantly,the PDT actions in mice tumor model was successfully monitored and visualized by CL-SO.