Application Of Activatable Optical Small Molecular And Self-assembled Nanoprobe In Molecular Imaging

Molecular imaging refers to the investigation of molecular abnormalities of disease in vivo,it usually exploits specific molecular probes and intrinsic tissue characteristics as the source of image contrast to provide the potential for early detection of disease and evaluation of treatment.The signal of activatable molecular probe is "off",which turns "on" after the stimulus of specific target with a relatively high signal-to-noise ratio for specific molecule imaging.Therefore,the study of activatable molecular probe has attracted extensive attention.In this dissertation,we designed several activatable small molecular probes and self-assembled nanoprobes for highly sensitive optical imaging analysis of biologically relevant important molecules(e.g.metal ions,anions,proteases)and self-assembly processes,which are expected to be used for the early diagnosis of related diseases or cancer.In chapter 2 of this dissertation,we reported a new pyridine-biquinoline-derivative fluorophore L for effectively sensing pyrophosphate(PPi)and monohydrogen sulfide(HS)in aqueous buffer and in living cells.L could selectively coordinate with metal ions(Mn+)in IB and IIB groups to form L-Mn+complexes with 1:1 stoichiometry,resulting in fluorescence quenching via photoinduced electron transfer(PET)mechanism.L-Zn2+ complex was applied to competitively coordinate with PPi to form a new "ate"-type complex,turning on the fluorescence by a 21-fold-increase.L-Cu2+ complex was applied for highly selective detection of HS-with an excellent sensitivity by 25-fold decomplexation-induced fluorescence increase.We successfully applied these two complexes for sequential imaging Zn2+ and PPi,Cu2+ and HS-in living cells,respectively.Since PPi and HS-occur in vascular calcification in positive correlation,our multifunctional probe L might help doctors to more precisely diagnose this disease in vivo in the future.In chapter 3 of this dissertation,we rationally designed two GGT-cleavable BL probes GluAmLH2(1)and Glu-p-aminobenzyloxycarbonyl-AmLH2(2),and successfully applied them for sensing GGT activity with high sensitivity and excellent selectivity both in vitro and in vivo.These results indicated that,although 2 had lower background BL signal than 1,GGT had higher catalytic efficiency for 1 than 2,and 1 was superior to 2 for sensing GGT activity in living cells and tumors.We envision that our probe 1 could be widely applied for the diagnosis of important GGT-related diseases in animal models in the near future.In chapter 4 of this dissertation,by co-incubating a hydrogelator precursor 1P and a CL agent 2 with ALP,we employed CL to directly characterize and image the simultaneous hydrogelation process.Kcat/KM values of the ALP-dephosphorylation reactions of 1P and 2 are close to each other,suggesting 2 is an ideal CL indicator for ALP-triggered hydrogelation of 1P.By altering the amount of 2,we found that at a 2/1P ratio of 0.071 the solution II reached its CL peak and gelling point simultaneously.Using an IVIS optical imaging system,we obtained the time-course CL images of 2 to track the simultaneous hydrogelation process of 1P in the same solution.Interestingly,even an anticancer drug(e.g.,doxirubicin)was added into the system,we still could use the CL to track the hydrogelation process.We envision herein that our CL method could be employed to track more biological events in the near future.In chapter 5 of this dissertation,by employing a click condensation reaction and rational design of a single quenched probe Cys(StBu)-Lys(Gly-Lys(DABCYL)-Gly-Gly-Arg-Arg-Val-Arg-Gly-FITC)-CBT(1),we developed a "smart" dual quenching strategy and applied it to detect intracellular furin activity with enhanced sensitivity.At physiological conditions,1 was subjected to reduction-controlled condensation reaction to form 1-NPs and its fluorescence intensity further dropped to 1/2.8 of its original.Upon furin cleavage in vitro,the dual quenched 1-NPs had fluorescence "Turn On" contrast 11-fold more than that of single quenched control probe FITC-Gly-Arg-Val-Arg-Arg-Gly-Gly-Lys(DABCYL)-GlyOH(1-P).Live cell imaging results indicated that 1 showed fluorescence "Turn-On" contrast 6.3-fold of that of 1-P for sensing intracellular furin activity.We envision that,by replacing the RVRR substrate with other enzyme-cleavable ones,our versatile "smart" dual quenching strategy could be easily adjusted for the detection(or imaging)of other intracellular enzymes' activity with enhanced sensitivity.