| OBJECTIVE:Ulcerative colitis?UC?,as a refractory disease with unknown etiology,is currently treated mainly by anti-inflammatory drugs like adrenocortical hormone,which effectively worked after oral absorption into blood.This kind of process may cause low drug concentration on inflammation.Increasing the drug concentration on inflammation may cause the strong side toxic effect and down the effect of drug.Another kind of treatment on UC is enema,which do exist an obvious disadvantage:drug can only reach to the inflammation of the descending colon and hardly to the inflammation of ascending colon and transverse colon.Meanwhile,patients have lower acceptance on enema because of its inconvenience.Therefore,oral colon-specific drug delivery system?OCDDS?,taking advantage of the unique pH,transit time and enzyme of gastrointestinal tract?GI?,attempt to achieve the colon targeting.However,OCDDS are targeting to the whole colon not the inflammation site,which means it would also have the same disadvantages that low drug concentration on inflammation,bad targeting to the inflammation and unsatisfactory effect.Based on that,colon inflammation targeting is the main direction on scientific research filed.And because of the character of surface charge of colon:the normal parts of colon are positively charged and the inflammation sites of colon are negatively charged.This study used electrostatic interactions as principle,prepare colon inflammation targeting pellets.We've chosen the colon inflammation targeting acidic polysaccharose which carry strong negatively charge and have high viscosity to prepare curcumin oral colon-inflammation-specific pellets.This kind of pellets can down the side toxic effect of drug,enhance the drug concentration on inflammation sites of colon,protect drug from metabolic enzymes in small intestine,maximize the drug effect and achieve the goal that drug slow controlled-release on inflammation sites of colon.METHODS:Lactoferrin,a cationic protein which can reflect the clinical severity of UC,was used as an index to judge the negatively charge intensity of acidic polysaccharose.Using coomassie blue chromogenic method under ultraviolet spectroscopy,established the detection and analyze method of lactoferrin in vitro.To obtain the acidic polysaccharose with highest negatively charge intensity among hyaluronic acid,chondroitin sulfate,sodium alginate and pectin.Using ex vivo adhesion experiment,taking dextran sulphate sodium salt?DSS?as model drug to establish acute UC mice model,inflammation sites of colon was obtained,incubated with the acidic polysaccharose to verify the negatively charge intensity of the acidic polysaccharose.After verification,taking the acidic polysaccharose,curcumin negatively charged self-microemulsion?NC?our team had prepared before and microcrystalline cellulose?MCC?as materials to prepare curcumin oral colon-inflammation-specific drug delivery pellets.Using Box-Behnken method,taking yield as index,the best recipe and technology of pellets was obtained.Under the best recipe and technology,pellets were prepared and the characters of them?like spherical degree and bulk density?were measured.A proper enteric coating material,whose character was stable in simulated gastric fluid,was chosen among Eudragit S100,L100,L100-55.Well-qualified pellets were coated with the proper enteric coating material to obtain enteric pellets.The colon targeting of Enteric pellets were detected using fluorescence imaging.RESULTS:Pectin had the highest negatively charge intensity,which could closely connect to the cationic protein lactoferrin and down the absorbancy of lactoferrin solution.It was chosen as the material to be verified.According to the results in ex vivo adhesion experiment,the fluorescence intensity of pectin group showed significantly difference to control group,which meant pectin had the colon targeting effect.And it could be sure that pectin was the proper acidic polysaccharose to prepare curcumin oral colon-inflammation-specific pellets.The best recipe was:NC:MCC=0.5,pectin:MCC=0.35.The best technology of pellets was:extrusion speed was 200 r·min-1,rolling speed was 2000 r·min-1,rounding time was4.5min,dried 15min to obtain the qualified pellets.The best recipe of enteric coating was:Eudragit S100 6.25g,triethyl citrate 0.63g and 1.25g talcum powder were completely solved in91.87g 95%ethyl alcohol.The speed of coating pan was 60rpm,the temperature was 60?,the coating weight was 15%.When the weight increment of pellets reached to 15%,turned the temperature to 80?and continually rolled coating pan for half an hour to get the compact enteric coating layer.And according to the results of fluorescence imaging,it could be concluded that the pellets without enteric coating released quickly once got into the stomach,the tendency of fluorescence intensity was weakening gradually.On the contrast,the enteric pellets showed a different tendency.The fluorescence intensity of enteric pellets barely showed at the beginning of experiment,some time later,the fluorescence intensity of enteric pellets appeared,gradually got stronger and to the top on 8h,then the fluorescence intensity was wearing off.We believe that the enteric pellets can target to colon and release drug to inflammation.CONCLUSION:Pectin,selected by lactoferrin model was the excellent acidic polysaccharose with highest negatively charge intensity.And it can be verified by ex vivo adhesion experiment that pectin group got the higher fluorescence intensity compared to control group,the difference was statistically significant?P<0.05?.What we can conclude that pectin has the strong bio-adhere and targeting to inflammation colon.The preparation method of pellets optimized by Box-Behnken experiment was stable.The model R2>0.9,P<0.001,which proved that the model was stable and significant.And this study has successfully prepared the pellets with higher yield and drug loading.The quality of pellets was up to standard.Eudragit S100was chosen as coating material to prepared enteric pellets.The enteric pellets and pellets were examined by fluorescence imaging.Compared to control pellets,enteric pellets showed completely trend in vivo and got the longer residence time,which means that enteric pellets owned higher bio-adhere to colon.Combined all the results,it can be concluded that the enteric pellets we've made would have the lower side effects,higher concentration on inflammation and better effect to UC.This research may provide a new way to similar studies in the future. |
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