| Objective: Irinorecan(CPT-11) used to treat the colorectal cancer andsmall cell lung cancer is a synthetic derivative of the plant alkaloid camptothecin with increased aqueous solubility. At present ,a irinotecan hydrochloride injection is called Campto.It is mainly used to treat advanced stage cancer of colon, and when the 5-FU is failed to cure completely, it can be used to cure. At the same time, using it to cure carcinoma of stomach and carcinoma of esophagus is doing many clinical trials, and from the present outcome, it will have a good future in the clinic. But its solution injection also have some toxic actions and side effects, such as: tardive diarrhea, gag, neutropenia, thrombocytopenia, membranitis, coryza, hypopiesia, vasodilatation, diaphoresis, ague, general malaise, dizziness, visual disorder, amydriasis, amydriasis, dacryorrhea, anhelation, muscle contraction, cramp, cacesthesia and so on. So it is very important for us to choose a good carrier in order to get high efficience and low toxic and side effects.Liposomes are composed of bimolecular leaflet of fatty substance and contain aqueous phase.They are avirulent and immunogenicity,and they can be degraded in biosystem.As a pharmaca carrier, they can reduce dosage and relieve toxic and side effect. The ordinary liposome will be phagocytized by RES, so they can only make medicine get these tissue and organ.But this character will limit their use for cancer of other tissue and organ.Meanwhile,it is proved that cationic liposomes as the carriers can target the medicines to the lung. This experiment through adding octadecylamine makes the liposome get cation,which can get targeted in lung and low concentration of irinotean in heart, kidney and myeloid. The cationic can get high efficience and low toxic and side effects, which is very important for the treat of small cell lung cancer.Irinotean is selected as the sample medicine to prepare the cationic liposome in order to get initiative targeted in the lung. Methods: On the basis of preliminary experiments,determining irinotecan cationic liposome preparation methods and prescription. Then through the single factor consideration to identify the factors affecting irinotecan cationic liposomes.The irinotecan cationic liposome was prepared by film dispersion method , ether injection method ,reverse-phase evaporation vesicles method and ammonium sulfate gradient method.The cationic liposome and free medicine were separated by using Sephadex G-50 column. According to the entrapment efficiency(EE),ammonium sulfate gradient method was selected to prepare cationic liposomes.The EE was taken as criterion to optimize the rate of lipid to cholesterol, the rate of drug to lipid, the rate of lipid to octadecylamine,the concentration of ammonium sulfate and the incubation temperature. On these basis, four factors and three levels orthogonal design was selected to optimize the formula and prepration methods of irinotecan cationic liposomes.According to analysis of range to finalize irinotecan cationic liposome best formula and prepration methods.Respectively mapping irinotecan cationic liposome, irinotecan liposome and solution in vitro release curves, using zero-order, first order, Higuchi and Weibull equation to fit and calculate the coefficient correlation.Taking pH, viscosity, particle diameter and so on as indexs to inspect the physical and chemical stability of irinotecan cationic liposome .A simple HPLC method with fluorescence detection was developed for the determination of irinotecan in rat plasma and mice tissue, Diamonsil C18 column (200×4.6 mm, 5μm) with the fluorescence detection set atλex 370nm andλem 530nm.The mobile phase was acetonitrile- citric acid (2.1% citric acid, pH was 3.8 setted by 30% natrium hydroxydatum, containing 0.2 % triethylamine) 40:60 v/v. Flow rate 1ml/min. The pharmacokinetic parameters were calculated by 3P-97 and statistical moment program. The medicine distribution of mice was investigated to evaluate targeting in tissues.Results: Ammonium sulfate gradient method of irinotecan cationic liposomes preparation is efficient with higher EE. The optimal prescription is lipid 400mg, cholesterol 133mg, octadecylamine 66 mg , irinotecan 40 mg and the concentration of ammonium sulfate is 3%. The entrapment efficiency was 86.82% and pH was 6.18. The size of the resulting liposome was 198.2nm.The irinotecan release behavior from irinotecan solution in vitro was in accord with weibull equation and the equation was as follows: ln[-ln(1-Q)]=1.0311lnt– 1.2435, r2=0.9918; The irinotecan release behavior from irinotecan liposome in vitro was in accord with first order,equation and the equation was as follows: Ln(1-Q)=-0.0704t+ 0.0407 , r2=0.9953 ; The irinotecan release behavior from irinotecan cationic liposome in vitro was in accord with weibull equation and the equation was as follows: ln[-ln(1-Q)] = 1.3771lnt– 4.3699, r2=0.9840。And at 6h and 12h, irinotecan solution can release 79.2% and 98.6%,while at 6h, irinotecan liposome and irinotecan cationic liposome can separately release 25.37% and 12.51%,and at 48h,they separately release 97.09% and 89.51%. so irinotecan liposome can delay release.The physical stability of irinotecan cationic liposome was shown as follows: when irinorecan cationic liposome was stored at 25℃in a month, the EE decreased by 35% and membrane of liposome produced conglutination and disruption; while it was stored at 4℃in a month, the EE decreased by 6.8% and taking slight flocculent precipitate.So the irinotecan cationic liposome should be stored at 4℃.The pharmacokinetic behavior was shown as follows:after caudal vein injection irinorecan cationic liposome, irinorecan liposome and irinorecan solution, the k of irinorecan cationic liposome was 0.21h-1, the k of irinorecan liposome was 0.16h-1, the k of irinorecan solution was 0.56h-1.So liposome preparation can reduce rate of elimination.The AUC of them were 20.43μg·h·ml-1,17.22μg·h·ml-1 and 11.43μg·h·ml-1.So the liposome preparation can improve bioavailability.The biodistribution of irinotecan in mice tissues showed that cationic liposome has the ability to initiatively accumulate in the lung. The relative ingest rate in lung of rats is 2.14 and T% is 33.18.Conclusion: Ammonium sulfate gradient method is chosen to prepare irinotecan cationic liposomes using soybean phospholipid,cholesterol and octadecylamine.These liposomes have the character of high envelopment ratio,well-distributed particle diameter and fine stability. Through pharmacokinetics we know that cationic liposomes can postpone the release of irinotecan,and in tissue disposition it is proved that irinotecan cationic liposomes have apparent target to lung.
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