| Photodynamic therapy (PDT) is a relatively new method for the treament of cancer that has received considerable attention in recent years. PDT relies on the selective accumulation of a photosensitizer (PS) into cancerous tissues followed irradiation of the diseased area. Upon irradiation, the excited states of the photosensitizer generates singlet oxygen (and other reactive oxygen species) which will kill or damage cellular components and ultimately leads to cell death. In the dissertation the fundamental features and recent progression for photosensitizer of PDT are described. PDT has some peculiar advantages compared with other treaments, which are that 1, PDT avoids systemic treatment and has no side effects in therapy; 2. PDT possess selectivity for treatment and may not damage normal tissue; 3. PDT could be used when surgery is not possible and also is repeatable for cancer treatment; and, 4, PDT is low cost and the therapy period is shortest. The advantages show that PDT is a prospective and worthy developing technology. The problems, however, exhibited from the current clinical PDT technology should be solved as soon as possible, which are mainly relative to PS being used. HpD is only a PS useds in clinical for PDT now, and is of some disadvantages. First, the long-wave length absorption band appears at 630nm (with a low extinction coefficient), the biological effects after irradiation at this wavelength occur only to a tissue depth of 5mm. Second, its nonselective accumulation in the tumor and slow drug metabolism makes the PS be retained in the body of patient for 2-3 months, which requires that the patient shields from bright light for long period. Finally, HpD is a mixture of its isomers,whichdoes not allow one to use only its active components. These defects have prevented PDT technology from extensive application. It, therefore, has been the urgent research subject at home and abroad to develop a new generation of PS.The dissertation focus on Hypocrellin A (HA), a new generation photosensitizer, which has a good development foreground and will be potential to used in clinic. Through analysed the spectrum properties and the photobleaching of HA, It is some significant reference data for clincial application that are provided. And it is hoped to be used in diagnosis and treatment on tumors. Some new experiment results are obtained and illustrated as following:1. The HA absorption spectra in different solvent were studied, especially in NS, Glucose saline and NS including 10% human serum.Two stronger absorption are showed in NS including 10% human serum and NS, but three in others. The absorption peaks in NS including 10% human serum are stronger than NS and Glucose saline. And have a Einstein shift above 10nm. The study has revealed that HA appeared Einstein shift under the relevant body environment. The spectra parameters provided basis for selecting light source of PDT. The strongest peak is between 460nm and 490nm.2. Effect on the absorption spectra by solution polarity and concentration were studied.There isn't an abviously regular change in the absorption peaks with the variety of solution polarity. No matter what concentration is, the change of the peak isn't found except change in absorption intensity. And no new band appears.3. Evaluating the photobleaching of HA by absorptionspectra.It has also three band in visible range after irradiation. But there is a movement about 7nm to short wavelength in band I, and no movement in band II and III, but III/I and II /I is down, especially, the intensity of band III decrease faster. Perhaps the reason is photosensitive molecular's self-oxidation.During the photobleaching, the color of HA got to jasmine, finally it wouldn't change. At first, the photobleaching was obvious, but after sometime, there is no change. Photobleaching's half lifetime, about 4h is drawn. When the concentration keeps no cahnge, the photobleaching time decreased with the increase of the power of light source.4. Effect of temperature, concentration,excitation wavwlength and intensity on fluorescence spectra were studied.It have two bands,stronger in 600nm and another in 650nm. The concentration have no effect on the proportion of two bands. At low tempreture, the spectrum is similar to the spectrum at normal tempreture. the proportion of two bands decreseaed. The shape of the spectra don't change with the excitation wavelength. But the excitation intensity will make the spectra change when it is enough high.Finally, HA is potential to be used in clinic andis proved to be efficient. But the study improves slowly, it is a long time that HA would be used in clinical treatment. So the pursuer in every field must work together. |
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