RESUMO
The aim of this work was to investigate guar gum/ethylcellulose mix coated pellets for potential colon-specific drug delivery. The coated pellets, containing 5-fluorouracil as a model drug, were prepared in a fluidized bed coater by spraying the aqueous/ethanol dispersion mixture of guar gum and ethylcellulose. The lag time of drug release and release rate were adjustable by changing the ratio of guar gum to ethylcellulose and coat weight gain. In order to find the optimal coating formulation that was able to achieve drug targeting to the colon, the effect of two independent variables (the ratio of guar gum to ethylcellulose and the coat weight gain) on drug release characteristics was studied using 3×4 factorial design and response surface methodology. Results indicated that drug release rate decreased as the proportion of ethylcellulose in the hybrid coat and the coat weight gain increased. When the ratio of guar gum to ethylcellulose was kept in the range of 0.2 to 0.7, and the coat weight gain in the range of 250% to 500%, the coated pellets can keep intact for about 5 h in upper gastrointestine and achieve colon-specific drug delivery. The pellets prepared under optimal conditions resulted in delayed-release sigmoidal patterns with T5% (time for 5% drug release) of 5.1-7.8 h and T90% (time for 90% drug release) of 9.8-16.3 h. Further more, drug release was accelerated and T90% of the optimum formulation pellets decreased to 9.0-14.5 h in pH 6.5 phosphate buffer with hydrolase. It is concluded that mixed coating of guar gum and ethylcellulose is able to provide protection of the drug load in the upper gastrointestinal tract, while allowing enzymatic breakdown of the hybrid coat to release the drug load in the colon.
RESUMO
PurposeTo study the effect of phospholipid on the ability of HDL3 mediated cholesterol efflux from rat skin fibroblasts. Methods At the present of phosphatidylcholine (PC) or sphingomyelin (SPM), to measure the changes of HDL3-mediated cellular cholesterol efflux, cellulax phospholipid content and balance between free cholesterol and cholesteryl ester.Results① BSA (control) ,HDL3,PC,SPM, PC + HDL3 and SPM + HDL3 group mediated 4.70 %, 31.55 %, 7.35 %, 8.06 %,42.95 % and 46.98 % of cellular cholesterol efflux from the cells respectively. ② After the incubation of the cells with BSA, HDL3, HDL3 +SPM and HDL3 + PC, the cellular phosphorous content in PC(PC-p) and SPM (SPM-p) were 20.02,5.56; 17.56,5.28; 18.62,7.00 and 22.50,5.52 μg/plate respectively. ③ After the incubation of the cell with PC and SPM, ratio of free cholesterol to total cholesterol were 49.65 and 59.57 respectively. The ratio was 48.64 before incubation.ConclusionsO PC and SPM couldn' t mediated directly cellular cholesterol effiux, but they could enhance significantly HDL3 mediated cellular cholesterol efflux, and this ability of SPM was stronger than PC. ① With cellular cholesterol efflux,a part of cellular PC went out of the cells, but the content of cellular SPM didn' t change significantly. ③ SPM could induce cholesterol ester to convert into free cholesterol in the cells.