Luminescence, Photochemical And Oxygen Sensing Properties Of Phosphorescent Photosensitizers-rare Earth Metalloporphyrins

Photodynamic Therapy?PDT?is one of the most advanced methods of cancer treatment.The measurement of its three elements?light,photosensitizer and oxygen?,helps to achieve precise treatment of cancer.The multifunctional photosensitizer-metalloporphyrin not only has imaging features but also room temperature phosphorescence emission for oxygen detection.However,the currently available phosphorescent metalloporphyrins are limited to platinum group metal porphyrins,while platinum group metal porphyrins have the following problems:?1?platinum-based ion imaging features are weak;?2?luminescence quantum yield is low;?3?the accuracy and stability of oxygen measurement need to be improved;?4?poor water solubility.In this paper,the luminescent properties and PDT applications of multifunctional phosphorescent photosensitizers-rare earth metalloporphyrins were systematically investigated.The luminescence and oxygen sensing properties of a series of palladium and porphyrins were studied and compared.Palladium and porphyrin porphyrin monomethyl ether?Pd-and Gd-HMME?were synthesized by thermal solvent method and characterized by mass spectrometry,Fourier infrared absorption and UV-visible absorption spectroscopy.The spectral analysis showed that the absorption and luminescence of porphyrins were red-shifted compared with palladium porphyrins,indicating that the excited states of porphyrins were lower than the corresponding palladium porphyrins.The oxygen intensity of Gd-HMME phosphorescence intensity and lifetime is larger than that of Pd-HMME.To understand this difference,the oxygen quenching rate constants of the two materials were calculated.It was found that the oxygen quenching rate constant of Gd-HMME was 4972.9 s^-1 and that of Pd-HMME was 26.4 s^-1.The large difference in oxygen quenching rate constants is the main reason for their differences in oxygen response.The analysis found that the energy balance between the lowest triplet energy level of Gd-HMME and the excited state energy level of oxygen is better.This is confirmed by the large singlet oxygen quantum yield of Gd-HMME.The enhancement and mechanism of the phosphorescence of Gd-HMME by imidazole and cerium ions are revealed.Imidazole is a hot solvent used in the synthesis of Gd-HMME,and can effectively enhance the phosphorescence of Gd-HMME.In the presence of imidazole,the continued addition of cerium ions will further enhance the phosphorescence,and a total of 40 times the enhancement effect is obtained in both cases.Spectroscopic analysis revealed that imidazole formed a protective medium and the degree of protection was further enhanced by the addition of cerium ions.The protective medium reduces the non-radiative relaxation by forming a rigid and ordered environment,enhancing the phosphorescence emission,while the protective medium also partially blocks the energy transfer between the Gd-HMME and the oxygen.This is confirmed by the decrease in the singlet oxygen quantum yield of Gd-HMME after the addition of imidazole.These results indicate that imidazole can act as a phosphorescent enhancer and a triplet protectant.A method for measuring dissolved oxygen based on the ratio of phosphorescence and fluorescence was studied.Firstly,a ratiometric system based on Gd-HMME phosphorescence and HMME fluorescence was developed.The fluorescence of porphyrin does not change with oxygen,while the phosphorescence of Gd-HMME is sensitive to oxygen.The relationship between the ratio between phosphorescence and fluorescence and the oxygen concentration was found to be linear.When the phosphorescence and fluorescence are comparable,the spectrum can be brought close to full scale by adjusting the integration time of the spectrometer,thereby simultaneously measuring the high signal-to-noise ratio of phosphorescence and fluorescence.The measurement uncertainty for oxygen at 62.5?M is 1.2?M,indicating that the system has a measurement range of up to 300?M and an accuracy of 1.9%.When measuring the oxygen concentration in different ranges,the appropriate Gd-HMME and HMME concentration ratio can be used to make the phosphorescence and fluorescence equivalent,thereby reducing the measurement uncertainty.A single molecule,hemoglobin monomethyl ether?Lu-HMME?,which has both phosphorescence and fluorescence emission,was designed.The phosphorescence and fluorescence of Lu-HMME in air-saturated solutions are on the order of magnitude.The phosphorescence intensity response to oxygen is approximately 4.6,and the uncertainty of the measurement system in air-saturated methanol solution is 0.06?M.The phosphorescence and photosensitivity of water-soluble porphyrin DVDMS and its rare earth metal porphyrins were studied.Gd-DVDMS can be used as a photosensitizer in photodynamics,a magnetic resonance contrast agent,and an oxygen indicator based on phosphorescence quenching.Since Gd-DVDMS has two porphyrin rings,its molar absorption absorption is twice as large as that of Gd-HMME.The Gd-DVDMS has a phosphorescence emission lifetime of 49?s at712 nm and a quantum yield of 0.015.It was found that the phosphorescence of the Gd-DVDMS was effectively quenched by oxygen:the phosphorescence intensity under air dissolution was 33%under oxygen removal conditions.It shows that Gd-DVDMS has potential application value for oxygen quantification in photodynamic process.The singlet oxygen quantum yield of Gd-DVDMS was measured to be 0.46.Gd-DVDMS is a multifunctional photosensitizer with many advantages over existing photosensitizers.