The Preparation And Character Of Cyclosporine A Polylactic Acid Microsphere For Allotransplantation Of The Trachea

The allotransplantation of the trachea is one of the important anticipated events in tracheal surgery, being regarded as an ideal technique for reconstruction of tracheal defect after extensive resection. Research on tracheal transplantation progressed sluggishly in the past years because of the subsequent severe stenosis and obliteration of the tracheal grafts. The major causes consist of ischemia which results in cartilaginous necrosis, chondrolysis and resorption, rejection of the tracheal grafts (epithelium, muscle,vasalium). Previous reports have described the ability of cyclosporine A (CsA) at tracheal transplantation. However, there are some problems with the treatment of CsA, the blood levels of CsA above the therapeutic range were related to adverse effects, such as nephrotoxicity and neurotoxicity. While the blood levels of CsA at lower than therapeutic levels would induce higher rates of organ rejection. One approach toward reducing the drug-specific and general adverse consequences of systemic immunosuppression, and thereby improving the clinical feasibility of the procedure, is the use of local aministration systems in multi-organ transplantation. The method of Cyclosporin A polylactic acid microspheres preparation was optimized through orthogonal experiment. The microspheres have been successfully prepared and sustained release of CsA from microspheres has been achieved. The character and the release kinetics of the microspheres was studied in vitro and in vivo.Objective: Orthogonal experiment was used to optimize the technique of Cyclosporin A polylactic acid microspheres preparation for allotransplantation of the trachea. To prepare Cyclosporin A polylactic acid microsphere and study the character of the microsphere.The CsA levels in rats whole blood and tracheal tissue were evaluated and compared between groups of local application and systemic administration.Methods: To prepare the Cyclosporin A polylactic acid microspheres using solvent evaporation method from an oil-in-water system. The microspheres were characterized for drug loading and entrapment efficiency by high-performance liquid chromatography(HPLC), checking the average size by particle size analyser and surface morphology by scanning electron microscopy (SEM). The release kinetics in vitro was studied using a modified dialysis. The CsA level in rat whole blood and tracheal tissue was evaluated and compared between groups of local application and systemic administration with fluorescence polarization immunoassay(FPLA).Results: An ideal technique of Cyclosporin A polylactic acid microspheres preparation for allotransplantation of the trachea was optimized through an orthogonal experiment. The relative importance of factors arranged in descending order was ratio of CSA to PLA> concentration of PVA > stirring time > concentration ot PLA.Studies showed discrete and spherical particles with smooth surfaces.The average particle size was 18.234um in diameter,with more than 80% of the microspheres falling in the range of 9.525-32.400μm.The drug loadings ranging was 34.51±0.63% with a high encapsulation efficiency (86.12±0.77%) determined by HPLC.In vitro release study revealed a profile of sustained release of cyclosporin A from CsA-PLA-MS.The accumulated release percentage of cyclosporin A microspheres were 40.8% in 30d. CsA level in rat whole blood could maintain a high level during the first two weeks, CsA level could maintain at about 200 ng/ml during the rest two weeks.Conclusions: The microspheres have been successfully prepared and release of CsA from the microspheres have been achieved. When CsA was locally administered, effective whole blood level could be achieved and it's level in the rat tracheal tissue was higher than that by systemic administration. an ideal technique to prepare cyclosporin A polylactic acid microspheres was found through orthogonal experiment.