Foundational Study On Photodynamic Therapy Of Zinc-bacteriochlorophyll

Nowadays, photodynamic therapy (PDT) has become a hot Point whichhas been broadly employed to diagnoses and therapy of tumorous andnontumorous diseases. Photo sensitizer plays an important role in PDT. Theoptical characteristics of photosensitizer have the directly influences oncurative effect of PDT. The characteristic absorption of the second-generationphoto sensitizer locates in 670 nm or 690nm. However, there are manydisadvantages of the second-generation photo sensitizer to therapy cancerssuch as the poor penetrable ability in tissues, the wide absorption spectrum invisible range and the obvious side-effects. In our study, we have synthesizedsome new photo sensitizers which have characteristic absorption in 750 nm.Because of their great penetrable ability, the new photo sensitizer can bedirectly used to diagnoses and therapy tumorous and nontumorous diseases.Moreover, the side-effects have decreased greatly. The mechanism of PDTand the bioactivities of the new photo sensitizers have been studied in theresearch as well.(1) Bacterialchlorophyll a was extracted by supersonic in ethanol fromRhodobacter sphaeroides, absorbed by French chalk, separated withDEAE-sepharose CL-6B(2.7×6.5)and Sepharose CL-6B(2.7×18). Bchla50mg/100g (wet weight) is obtained. The synthesis of transition metal (Cu,Zn, Co, Fe) was investigated by using bacteriochlorophyll a as ligand. Theultraviolet-visual spectrum and the fluorescence spectrum of thesecompounds were analyzed respectively. The conclusions showed that thecharacteristic absorption of different metal-bacteriochlorophyll a appearedbiggish red and blue shift. The most remarkable Cu-BCA' characteristic absorption had blue shift 97 nm and red shift 29 nm. In addition, allmetal-bacteriochlorophyll a but Cu-BCA emitted fluorescence, and Zn-BCAhad red shift 57 nm and blue shift 80nm, the biggest emission wavelength ofZn-BCA was 770 nm.(2) Liposomes were introduced to be a drug carrier because of smallpolarity's metal-bacteriochlorophyll. It could be one of the most effectivemethods that could improve drug targer and minish the side effects of body.In the experiment, liposomes were sized by extrusion through 100nm porepolycarbonate membrane and then incubated with Zn-BCA. The procedureprovided unilamellar liposomes with a mean diameter and high temperatureof phase shift at 50℃. The recovery rates of the liposomes were high(＞95.00%). The relative standard deviations (RSD) of intra-day and inter-daywere less than 5.84%. The envelop rates were more than 53.00%.(3) MTT colorimetry was used to investigate parameters ofZn-BCA-PDT to HL-60 leukaemic cells, which contained Zn-BCA dose,dark incubating time, photoreaction time and light wavelength, Theoptimized comditions of experiment of light sensitization of Zn-BCA-PDT toHL-60 were observed, cell density was 1×10~5/mL; Zn-BCA dose was 10μg/mL; dark incubating time and photoreaction time were 3 h and 50 min;light wavelength was 800 nm, respectively.(4) As a photosensitizer in PDT, the key factor of effecting the curativeeffect of Zn-BCA were high selective in tumor tissue and cell. Therefore,It'distributing in animal tissues would influence not only the curative effectbut also the side effect on common tissue. In this article, spontaneityfluorescence of Zn-BCA was used to observed metabolism of Zn-BCA inmice tissues. The results showed that metabolizing of Zn-BCA in tissue werevery fast, and it' fluorescence intensity were very low after 5 hours.(5) Kunming mice were inoculated to execute tumor mice modelthrough injected into HL-60 leukaemic cells, and treated with 0.25mg/Kg and1.0 mg/Kg Zn-BCA, respectively. The photodynamic effect and side effect ofZn-BCA were remarkably observed. The results showed that the survive time of tumor mice which were treated with PDT were significantly prolongedcompared with the control group. Injected with 1.0 mg/kg Zn-BCA liposomeand immediately photoreacted without dark incubation, mice presentedstrong skin photosensitive effect and short survive time compared withcontrol group. It's suggested that the curative effect of Zn-BCA-PDT wasprominent. No remarkable skin photosensitive effects were observed in tumormice which were carried out PDT after 4 hours' dark incubation.