Research To Quantum Dots As Photosensitizer Mediating Photodynamic Therapy Of Tumor In Vitro

Nearly half a century, tumor itself has seriously threaten human health as a common disease and frequently-occurring disease. Since 1990s, main cause of death are malignant tumor, cerebrovascular disease and respiratory apparatus disease in our country. At the present, many traditional treatments to tumor have showed a variety of deficiency. So it need be found more efficient treatment to tumor. Photodynamic treatment which can treat malignant tumor, is a new developing technique in latest 20 years. Its principle is photosensitizer selectively accumulates and retention in tissue, under the illumination of special wavelength, tumor tissue can be killed by photochemical or photobiological reaction, thus to achieve the purpose of partly treating tumor. By compared with traditional surgery, radiotherapy and chems, PDT has the characters of having relative specificity to kill tumor cell, little normal tissue damage and few toxicity and by-effect, and so on. So this method suitably applies to the patients which are old, weak, inoperableness and vein chemo. There has been 30 years since PDT has come out. Because of its merits of utility, safe and low cost, it has been a main treatment to tumor in Europe, U.S.A and Japan. In our country, PDT is also a important method to treat tumor. Photosensitizer, as a important factor in PDT, has been studied more and more. Nowadays, photosensitizers having applied in clinic are mainly porphyrin or its derivate. Although these photosensitizers have achieved definite effect, there are still many shortages. So new and high efficient photosensitizers are being studied by scientific research groups all over the world.In this paper, because Quantum dots possess several characteristics that make them potential photosensitizers, here, quantum dots, as a photosensitizer, mediating photodynamic therapy to study the effect in vitro. Objective to probe growth inhibiting effect of tumor cell Bel7402 treated by photosensitivity reaction mediated by quantum dots, and to study new type of photosensitizes Methods (1) adding different concentrations of quantum dot to medium, then illuminated by light source, cell survival rate is determined by MTT reduction assay. ( 2 ) with same concentration of quantum dots, by different light energies, cell survival rate is determined by MTT reduction assay. (3) only adding adding different concentrations of quantum dot to medium, cell survival rate is determined by MTT reduction assay. (4) only illuminated by light source, cell survival rate is determined by MTT reduction assay. (5)using acridine orange staining and flow cytometry determining DNA contents of cells detect the apoptosis of tumor cells resulting from PDT. Results with constant light energy, concentration higher, cell survival rate lower. It shows that photosensitivity reaction of quantum dot has strong lethal effect and katogene to tumor cell Bel7402. This effect is related to the concentration of quantum dot itself in some light energy range. Using quantum dot or light separately, there are no significant lethal effect to tumor cell. It is showed by acridine orange staining that it comes out apoptotic body in the tumor cell Bel7402 via PDT. To use flow cytometry determining the percentage of apoptotic cells, the result is the time after PDT longer, percentage of apoptotic cells higher. Conclusions quantum dots can be used as a perspective photosensitizer with low toxicity. It has probability to apply in photodynamic therapy of tumors.