Enhancement of the transdermal delivery of catechins by liposomes incorporating anionic surfactants and ethanol

The aim of this study was to develop and evaluate liposomal formulations encapsulating tea catechins, which possess antioxidant and chemopreventive activities. Liposomes were characterized for size, zeta potential, and entrapment efficiency. Both in vitro and in vivo skin permeation were examined using nude mouse skin as a model. The results suggested that the liposomal composition plays an important role in affecting the efficiency of transdermal catechin delivery. Incorporation of anionic surfactants such as deoxycholic acid (DA) and dicetyl phosphate (DP) in the liposomes in the presence of 15% ethanol increased the (+)-catechin permeation by five to seven-fold as compared to the control. The flexibility of bilayers is suggested as an important factor governing the enhancing effect of liposomes. Intercellular spaces within the stratum corneum but not shunt routes are the major pathways for catechin delivery from liposomes. (+)-Catechin and (−)-epicatechin are isomers which showed similar encapsulation efficiencies and skin permeation in liposomes. (−)-Epigallocatechin-3-gallate showed the highest encapsulation rate and in vivo skin deposition level in liposomes among all catechins tested. The stability and in vitro tranepidermal water loss test indicated the safety of the practical use of liposomes developed in this study.     

甲氨喋呤脂质体药物释放动力学研究

本文应用荧光分光光度法研究了甲氨喋呤脂质体冻干粉针在几种输液中药物释放动力学。结果表明:甲氨喋呤脂质体的药物释放速率符合一级动力学方程。甲氨喋呤脂质体在不同输液中药物释放速率常数不同。温度升高、药物释放速率常数增大。     

An effect of antibiotic amphotericin B on ion transport across model lipid membranes and tonoplast membranes

A pH sensitive fluorescence probe piranine trisulfonate, entrapped inside small unilamellar liposomes formed with egg yolk phosphatidylcholine, was applied to investigate effect of polyene antibiotic amphotericin B (AmB) on proton transport across lipid membranes. Time dependencies of fluorescence-monitored pH changes inside lipid vesicles, upon sudden acidification of the liposome suspension, were analyzed in terms of two-exponential kinetics. It appears that addition of AmB at 3 mol%, with respect to lipid, considerably increases the rate constant of the fast component of proton transport (a change from (60 to 149) x 10(-3)s(-1)) and decreases the rate constant of the slow component (a change from (11 to 5) x 10(-3)s(-1)). Incorporation of 0.1 mol% AmB results in the decrease of both parameters (to (33 and 2) x 10(-3)s(-1), respectively). The increase in the rate of proton transfer across the lipid membrane is interpreted as related to the formation of membrane channels by AmB, at higher concentration of the drug or nonspecific destabilization of the membrane structure. At low concentrations, at which formation of molecular structures of AmB is not possible, the antibiotic molecules are oriented horizontally with respect to the plane of the membrane and act in making the membrane more compact and less permeable to ions. The presence of sterols (cholesterol, ergosterol and cholesterol dimer) in the lipid phase, in the concentration 3 mol% and lower, decreased the rate constants of proton transfer across the membranes but did not influence significantly the effect of AmB on the ion transport. The presence of AmB in the bathing solutions of tonoplast membranes isolated from Conocephalum conicum at the concentrations range 1 x 10(-7) to 3.6 x 10(-5) does not influence considerably the ion current, as monitored by means of the patch-clamp technique.     

RGD-targeted paramagnetic liposomes for early detection of tumor: in vitro and in vivo studies

Magnetic resonance molecular imaging has emerged as a potential approach for tumor diagnosis in the last few decades. This approach consists of the delivery of MR contrast agents to the tumor by specific targeted carriers. For this purpose, a lipopeptide was constructed by using a cyclic RGD peptide headgroup coupled to palmitic acid anchors via a KGG tripeptide spacer. Targeted paramagnetic liposomes were then prepared by the incorporation of RGD-coupled-lipopeptides into lipid bilayers for specific bounding to tumor. In vitro, study demonstrated that RGD-targeted liposomes exhibited a better binding affinity to targeted cells than non-targeted liposomes. MR imaging of mice bearing A549 tumors with the RGD-targeted paramagnetic liposomes also resulted in a greater signal enhancement of tumor compared to non-targeted liposomes and pure contrast agents groups. In addition, biodistribution study also showed specific tumor targeting of RGD-targeted paramagnetic liposomes in vivo. Therefore, RGD-targeted paramagnetic liposomes prepared in the present study may be a more promising method for early tumor diagnosis.     

Degradation Kinetics of Water-Insoluble Lauroyl-lndapamide in Aqueous Solutions: Prediction of the Stabilities of the Drug in Liposomes

The aim of this study was to explore the degradation kinetics of water-insoluble lauroyl-indapamide in solutions and predict the stabilities of lauroyl-indapamide encapsulated in liposomes. Buffer-acetone (9:1) was used as the reaction solution and the reaction temperature was maintained at 60 degrees C. The correlation of the apparent degradation constants (k(obs)) of lauroyl-indapamide in liposomes and in buffer-acetone solutions at different pH has been explored. The degradation of lauroyl-indapamide in solutions was found to follow pseudo-first-order kinetics and was significantly dependent on the pH values. Lauroyl-indapamide was the most stable at pH 6.8, increasing or decreasing the pH of the solutions would decrease its stabilities. Buffer concentration had some effects on the stabilities of lauroyl-indapamide. The degradation active energies Ea were 68.19 kJ x mol(-1), 131.75 kJ x mol(-1) and 107.72 kJ x mol(-1) at pH3.6, 6.8 and 12 respectively in acetone-free buffer solutions (0.05M) calculated according to the Arrhenius equation with the extrapolation method. The apparent degradation constants (kobs) of lauroyl-indapamide in liposome and in buffer-acetone (9:1) solutions showed a good correlation at different pH levels, which indicates that the stabilities of the drug that dissolved in acetone-buffer mixture solutions can be used to predict the stabilities of the drug in liposomes as well.     

尿激酶免疫脂质体靶向溶栓治疗兔肺动脉血栓栓塞

目的 观察以抗纤维蛋白D-二聚体单克隆抗体(DDmAb)为靶向装置的血栓靶向尿激酶(urokinase,UK)免疫脂质体(liposome,Lip)的溶栓效果.方法 新西兰大白兔32只,随机分为4组,每组8只,每只兔均采用自体血栓栓子颈静脉注入法建立急性肺动脉血栓栓塞模型.各组经股静脉输入不同溶栓剂进行溶栓治疗,通过观察右心室压变化及比较肺内残留栓子评价各组溶栓疗效.4组分别为阴性对照组(输入TBS缓冲液),阳性对照组(输入15万IU/kg UK),UK-Lip组(输入3万IU/kg尿激酶脂质体,反相蒸发法制备),DDmAb-UK-Lip组(输入3万IU/kg尿激酶免疫脂质体,戊二醛交联法连接UK-Lip和DDmAb制备).结果 栓塞后各组右心室压均明显升高(P均<0.01),平均升高(6.75±6.82)mm Hg(1 mm Hg=0.133 kPa).阴性对照组溶栓结束时右心室压[(40.15±11.22)mm Hg]与溶栓即刻[(41.67±14.23)mm Hg]相比下降轻微,阳性对照组和DDmAb-UK-Lip组降到与正常近似[阳性对照组和DDmAb-UK-Lip组溶栓结束时与栓塞前右心室压分别为(34.71±8.67)mm Hg比(33.98±9.32)mm Hg和(30.65±6.67)mm Hg比(30.77±6.85)mm Hg,P均>0.05],UK-Lip组情况居于阴性对照组和阳性对照组及DDmAb-UK-Lip组之间.阳性对照组及DDmAb-UK-Lip组栓子溶解最充分,残留柃子数近似(P>0.05),UK-Lip组栓子部分溶解,阴性对照组栓子未溶解.阳件对照组的心、肝、肾组织明显出血,其他组内脏未见明显病理学改变.结论 DDmAb-UK-Lip治疗急性肺动脉血栓栓塞的尿激酶用量仪为单独应用尿激酶的1/5即达到相似的溶栓效果,且不良反应较少,以DDmAb-UK-Lip进行靶向溶栓可能是肺动脉血栓栓塞的一种理想溶栓方式.     

CA02脂质体注射液大鼠长期毒性试验

目的：观察大鼠连续腹腔注射CA02脂质体产生的毒性反应与靶器官损害的可逆性.方法：设高、中、低剂量组和溶剂对照组,分别腹腔注射给予CA02脂质体注射液45.0,22.5,11.25 mg·kg^-1和等容量生理盐水（NS）对照品,通过对大鼠血液学、血液生物化学和病理靶向相关指标的观察,考察CA02脂质体对大鼠的毒性反应及程度.结果：连续腹腔注射CA02脂质体13周,动物全部存活,高剂量组大鼠PLT降低（P＜0.01）、CREA降低（P＜0.05）、TCHO升高（P＜0.01）较溶剂对照组比较的差异有统计学意义,但停药4周后能恢复正常.中、小剂量组未见明显毒性反应.停药后各剂量组均未见迟缓性毒性发生.结论：大剂量[45.0 mg·（kg·d）^-1]（相当于临床人用量的450.0倍）CA02腹腔注射对肾功能有一定的损害性,但为可逆性.     

猴头菇多糖脂质体包封率的测定方法及其稳定性研究

目的对猴头菇多糖脂质体进行质量和稳定性评价,测定猴头菇多糖脂质体包封率和进行脂质体稳定性考察。方法采用超滤法分离脂质体与游离药物;采用紫外分光光度法,最大吸收波长为（625±1）nm,测定药物含量,计算包封率;分别在40、60、80℃下对脂质体的化学稳定性和物理稳定性进行考察。结果超滤法能很好的将脂质体与游离药物分离,游离药物的平均回收率为96.3%,加样回收率为95.9%,脂质体不能透过超滤膜;加速试验中40、60℃下稳定性较好。结论该方法可用于猴头菇多糖脂质体的质量控制。     

Synergistic targeted delivery of payload into tumor cells by dual-ligand liposomes co-modified with cholesterol anchored transferrin and TAT

This study was mainly focused on developing a dual-ligand liposomal delivery system to enhance both targeting specificity and cellular uptake. The specific ligand transferrin (TF) and the cationic cell-penetrating peptide TAT were connected with cholesterol via a polyethylene glycol (PEG) spacer to prepare the dual-ligand liposomes (TAT/TF-PEG-LP). Then the in vitro cellular uptake by three kinds of cells that possessed different expressing levels of transferrin receptor (TFR) and the in vivo delivery efficiency were evaluated. Compared to the single-ligand TAT or TF modified liposomes (TAT-PEG-LP or TF-PEG-LP), TAT/TF-PEG-LP exhibited the enhanced cellular uptake and selectivity via the synergistic effect of both ligands in vitro. The ex vivo fluorescence imaging of tumors, the qualitative observation of tumor frozen section and the quantitative determination of cellular uptake in tumor tissues altogether showed the in vivo delivery efficiency of TAT/TF-PEG-LP was higher than that of other liposomes. In conclusion, the dual-ligand liposomes co-modified with TF and TAT possessed a strong capability for synergistic targeted delivery of payload into tumor cells both in vitro and in vivo.     

Encapsulation of ATP into liposomes by different methods: optimization of the procedure

Different methods and conditions for ATP incorporation into PEGylated liposomes were compared in order to obtain a preparation with a maximized ATP content. Such a preparation may find the application for the in vivo treatment of ischemic tissues suffering from an insufficient ATP supply. Several different methods of liposome preparation and purification were used and HPLC was employed to determine the concentration of ATP in the liposomes. Thin lipid film hydration produced vesicles with the lowest ATP encapsulation (ca. 5?mol%). A pH gradient method yielded liposomes with ca. 10?mol% of ATP. Reverse phase evaporation and freezing-thawing methods resulted in a maximum entrapment of ATP on the level of 36–38?mol%. The freezing-thawing method was chosen for further investigation because of its simplicity and absence of a need to use organic solvents. The separation of the non-entrapped ATP by gel-filtration, centrifugation or dialysis yielded virtually identical liposomal preparations. The incorporation of PEG (as PEG-distearoyl phosphatidylethanolamine, PEG-DSPE) into the liposomal membrane decreases the quantity of the entrapped ATP (from 38?mol% for liposomes with 0.5?mol% of PEG-DSPE to only 17?mol% for liposomes with 5?mol% of PEG-DSPE).