| Objective: First, to prepare carboplatin-loaded PLGA microspheres (CBP-PLGA Ms) for intra-tumoral injection (i.t.). Then the CBP-PLGA Ms would be injected directly in human pancreatic cancer in nude mice guided by ultrasound, and the anti-tumor effects would be evaluated. Our purpose is finding a novel therapy method for pancreatic cancer .Method:W/O/W emulsion solvent evaporation method and uniform test design were applied to optimize the formulation and procedure in the preparation of CBP-PLGA Ms, then physical characteristics and drug loading (DL) of the microspheres and release time of carboplatin from the Ms in vitro were tested. Also the subcutaneous implanting nude mice model of human pancreatic cancer was established successfully with sw1990 cell strain. Its ultrasound imaging and biological characteristics including the curve of tumor growth were studied by high frequence ultrasound (HFU). Then 20 mice was divided into 4 groups of CBP-PLGA Ms, carboplatin and blank microspheres mixture(CBP+Ms), free CBP and 5% glucose injection(5%GS). Intra-tumoral injections were performed respectively. The changes of tumor growth and ultrasound imaging were observed every 5 days, and blood changes were checked from 3 to 15 days after i.t. And pathology was examinated at the end of 30days.Result : The optimum factors of preparation of CBP-PLGA Ms were 10% CBP solution 1.5ml, PLGA concentration 2.5% in dichloromethane, stirring speed 1000 r/min, and the ratio of oil in water 1:5. The CBP-PLGA Ms were suitable for i.t. due to the rate of 96.7% of microspheres smaller than 100μm. in particle size.The DL was 10.16%, and release time of CBP from the microspheres was over 10 days. The human pancreatic cancer imaging in nude mice was low-echo and an-theca and clear border node. The CDFI and pathologic examination showed the vasculature was very rich in tumor. The suitable time for observation or injection was from 15 days to 20 days after implanting. The tumor growth double time (DT) of group of CBP-PLGA Ms was -33.9days, the difference from the other groups was significant (p<0.0001). The DT of those groups of CBP+Ms, free CBP, 5%GS were 4.65days, 4.32 days and 2.39 days respectively. The HFU also observedinjection process of CBP-PLGA Ms and its imaging characteristics in tumor, which was hyper-echo at the early stage and weakened bit by bit to low-echo at the end of 30 days. The tumor imaging of experimental group was unequal low-echo or weak-echo node with unclear border. The sign of color flow becomes insufficiency. The amount of WBC, RBC and PLT in the groups of CBP+Ms, free CBP became less after i.t., and lower than the group of CBP-PLGA Ms, p<0.05. The pathologic examinations showed that big coagulation necrosis masses with small colliquative necrosis and cell vacuolation were observed in the tumor in experimental mice, these signs were significantly different from the others. A few microspheres were found in some tumor tissues in the groups of CBP-PLGA Ms and CBP+Ms, which showed that the microspheres could be degradable slowly over 30 days in vivo.Conclusion: CBP-PLGA Ms can be used to injection in animal experiment,due to its good physical characteristics and degradation. Because of sustaining degradation of microspheres, the CBP can cause tumor to necrosis and vacuolation effectively and continously in vivo. HFU is sensitive, convenience and accurate using for observation on human pancreatic cancer in nude mice. The method, intra-tumoral injection with CBP-PLGA Ms guided by ultrasound, should be a new pathway using for therapy pancreatic cancer.
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