Fluorescent Probes For Nitric Oxide And Reactive Oxygen Species Based On1,8-naphthalimide

Fluorescent probes can transfer the information generated from the processes of molecular recognition into fluorescent signals. The advantages of fluorescent probes are as followed:high selectivity down to the single molecule; detection in situ with fluorescence imaging; high resolution down to subnanometer and submillisecond, etc. Compared with intensity-responsive fluorescent probes, ratiometric ones can observe the changes in the ratio of the intensities of the two emission wavelengths as the change of the concentration of the substrate, therefore providing built-in correction and reducing the inferences.4-amino or4-hydroxy-1,8-naphthalimide fluorophore with a pull-push electron system is characterized by the intramolecular charge transfer (ICT). When the electron-donating ability of4-amino or4-hydroxyl group in1,8-naphthalimide changes, a shift in the emission wavelength can be expected. In this thesis, a series of1,8-naphthalimide fluorescent probes based on the ICT mechanism were designed and synthesized.A fluorescent probe, termed DAN, for sensing nitric oxide (NO) based on the structure of1,8-naphthalimide was designed and synthesized using specific reaction of o-phenylenediamino with NO to generate triazole. The probe DAN can be obtained through simple synthsis which exhibits high sensitivity (19nM) and selectivity in response to NO. DAN showed a remarkable enhancement in the emission that is160-fold increase after the addition of NO. Meanwhile, the solution color changed from yellow to colorless. Thereofore, the probe DAN can detect NO in dual channel of fluorescence and colorimetric menthod. In addition, DAN was applied to HT29cells to make the fluorescence imaging and the results demonstrated that DAN is cell-permeable and can detect intramolecular NO.A ratiometric and colorimetric fluorescent probe A for detection hydrogen peroxide (H2O2) was designed and synthesized based on the ICT mechanism. Using the specific reaction of the boronate with H2O2, the boronate was derectly tethered to4-position of1,8-naphthalimide to generate the probe A. The probe A can be synthesized by two steps from4-bromo-1,8-naphthalimide. The boronate was hydrolyzed by H2O2to produce4-hydroxyl-1,8-naphthalimide which dehydrogenized under physiological condition to increase the electron-donating ability. The result shows a150nm red-shift in the emission wavelength and a remarkable change in the fluorescence colored from blue to yellow green. The maximum absorption wavelength redshifts from346nm to450nm accompanied by the change of the solution color from colorless to yellow green.A ratiometric fluorescent probe B for superoxide (O2·-) ion was designed. Using specific hydrolysis reaction of O2·-with phosphate, dipenylphosphate was induced to4-hydroxyl-1,8-naphthalimide to produce4-phosphate-1,8-naphthalimide. However, the probe B was hydrolyzed during the separation and purification process on the silicagel column, and the reason for that was analyzed.A fluorescent probe C for sensing Cu2+based on the ICT mechamism was developed. On the basis of the former work in our research group, the ligands,2-(N-phenylamino)-ethylamino and2-(N-phenylamino)-acetamino, were induced to4,5-positions in1,8-naphthalimide to form the probe C. After the addion of Cu2+, there was little change in the emission wavelength and the intensity of the probe C. The mechanism of the binding mode of the probe C and the addition of Cu2+was proposed.