Nitric Oxide-responsive Probe Based On Dihydropyridine And It's Application In Molecular Imaging

Nitric oxide(NO),a kind of signaling molecule plays a extremely important role in living organisms and participates in many physiological processes.NO,a lipophilic molecule is easy to penetrates cell membrane,and it diffuses following the concentration gradient.The detection of NO and the application to nitric oxide properties can provide a new strategy for molecular imaging.The 1,4-dihydropyridine and NO can react specifically,and the products are different depending on the substituent at the 4-position.When the 4-position substituted with a benzyl group,the C-C bond between the benzyl moiety and the dihydropyridine moiety will cleave after the reaction of the 1,4-dihydropyridine with the NO.By using this cleavage reaction,application in fluorescence imaging and nulcear imaging has been validated in this dissertation.A 4-benzyl substituted 1,4-dihydropyridine was synthesized.it was proved that the product of reaction between nitric oxide and 4-benzyl substituted 1,4-dihydropyridine is aromatized pyridine and benzyl radicalTo realize real-time detetion of NO in vivo,a 4-position benzyl-substituted 1,4-dihydropyridine was designed and synthesized as a linker.Based on the fluorescence resonance energy transfer mechanism,the NO fluorescent probe DHPFQ was composed by a fluorophore FITC and the quencher DABCYL which were linked to two ends of the dihydropyridine.DHPFQ can react with NO quantitatively in solution,and can detect NO produced by exogenous NO donor drug nitroprusside in HeLa cells,and can detect endogeous NO in Raw264.7 macrophages,and the fluorescence intensity would decrease by adding NOS inhibitor.DHPFQ is the first fluorescent probe to achieve real-time fluorescence detection in mammals,and can give a semi-quantitative result.Furthermore,the dihydropyridine could link different fluorophores and corresponding quenchers according to different requirments to adjust fluorescent imaging under different conditionsTo improve the contrast ratio of nuclear imaging and reduce the radiation dose in non-target organs,this dissertation first proposed the concept of "On/Off" of radioactive signals by taking advantage of the high sensitive response characteristics of dihydropyridine and NO.radiolabeled nanoparticles NP-3 was designed and synthesized.Dihydropyridine was linked between gold nanoparticles and 131I.After injection,NP-3 was entiched in mice liver,and "turn the radioactive signal on".After i.p.injection of exogenous NO drug glycerin trinitrate(GTN),liver metabolized GTN to generate NO,and NO cut off the dihydropyridine linker between nanoparticle and the radionuclide to make the radioactive moiety detached from nanoparticle and cleared rapidly,and "turn the radioactive signal off".The radioactivity in heart,blood,kidney,intestine,lung in the control group was 12.1 times,8.5 times,11.5 times,8.3 times and 6.0 times that of the GTN treated group after 1 h injection of saline and GTN respectively.The radioactivity in the heart,blood,kidney,intestine and lung of the control group was 9.1 times,14.4 times,11.1 times,9.9 times,5.0 times that of the GTN treated group after 2 h injection of saline and GTN respectively.The cut-off part distribution caused the radionuclide secondary distribution.The radioactive uptake of the liver is first decreased,then increased,and finally lowered.In the future,the improvement of radioactive labeling method can accelerate the in vivo clearance rate of labeled small molecules after the cleavage of bonds.The change in the internal irradiation dose after the clearance was simulated by calculation,and it was found that the amount of internal radiation absorbed by the mice injected with nitroglycerin was 48%of the mice injected with physiological saline in the control group,although the secondary distribution.