Comparative pharmacokinetics of breviscapine liposomes in dogs, rabbits and rats

AIM: To compare pharmacokinetics of intravenous breviscapine liposomes in Beagle dogs, rabbits and rats. METHODS: Six Beagle dogs, 6 rabbits and 12 rats were intravenously administrated with breviscapine liposomes and commercial injection (breviscapine solution) by the crossover design (two periods), respectively. Plasma concentration of scutellarin, the main active component in breviscapine, at different time intervals was determined by reverse phase-HPLC. The pharmacokinetic parameters including area under the curve (AUC), clearance (CL(s)) and volume of distribution (V(c)) were calculated. RESULTS: The plasma concentration-time profiles were fitted to a two-compartment model. Breviscapine liposomes exhibited significant difference from injection in CL((s)) and AUC, examined by a one-way analysis of variance (ANOVA). With regard to both breviscapine liposomes and commercial injection (free breviscapine), the logarithm values of AUC, CL(s) and V(c) were all related to the logarithm of the body weight by the allometric equation: Y=axW(b). CONCLUSION: The allometric equation might be applied to extroplate dosage for human from animal data and also for dosage adjustment of breviscapine liposomes in order to achieve same AUC as commercial injection. Compared with the breviscapine solution, breviscapine liposomes delivered more scutellarin into the plasma.     

注射用灯盏花素脂质体在Beagle犬体内的药代动力学

目的制备灯盏花素脂质体，研究灯盏花素脂质体在Beagle犬体内的药代动力学。方法采用双周期交叉试验法，6只Beagle犬分别单剂量(以灯盏乙素计为28 mg/只)静脉注射自制灯盏花素脂质体和市售普通注射液，用反相高效液相色谱法测定不同时间血浆中灯盏乙素的浓度，采用3P97计算药代动力学参数，并进行统计学分析。结果脂质体和市售注射液的T_1/2α分别为(4.4±0.7) min和(1.8±1.3) min；T_1/2<>分别为(55±27) min和(28±23) min；V_c分别为(1 580±265) mL和(2 460±2 200) mL；CL_s分别为(88±10) mL·min^-1和(324±69) mL·min^-1； AUC_0-720分别为(363±42) μg·min·mL^-1和(102±19) μg·min·mL^-1。两种制剂的T_1/2α，CL_s及AUC_0-720经方差分析后均存在极显著或显著性差异。结论与市售普通注射液相比，灯盏花素脂质体Beagle犬静脉注射给药后，大大提高了血药浓度，显著改善了灯盏乙素原药的药代动力学性质，具有缓释作用。     

In vivo evaluation of doxorubicin carried with long circulating and remote loading proliposome

Long circulating and remote loading proliposome (LRP-L) was a kind of transparent solution and composed of soybean phosphatidylcholine (SPC), cholesterol, polyethylene glycol derivative of distearoylphosphatidyl ethanolamine (PEG-DSPE) and oleic acid sodium salt. When LRP-L was mixed with 0.9% NaCl aqueous solution containing doxorubicin (DXR), liposomes formed and automatically loaded DXR, in which sonication and extruders were not needed. The average diameter of the liposomal DXR in saline was 129.0+/-1.9 nm and the encapsulation efficiency was 98.1+/-0.6%. The pharmacokinetics, biodistribution, acute toxicity and anticancer effect of DXR carried with LRP-L (LRP-L-DXR) were studied. The plasma concentration-time curves of DXR were best fitted to the triexponential decay curves. The area under the plasma concentration-time curve (AUC) of LRP-L-DXR was 22 and five times of free DXR (F-DXR) and conventional cardiolipin liposomal DXR (CL-DXR), respectively. Following i.v. administration, the biodistribution of LRP-L-DXR in the heart and the liver, unlike that of CL-DXR, was not greater than that of F-DXR. However, the biodistribution of LRP-L-DXR in the spleen was less than that of CL-DXR and greater than that of F-DXR. The acute toxicity of LRP-L-DXR was decreased compared with that of F-DXR. The anticancer effect of LRP-L-DXR was significantly increased compared with that of F-DXR in the ascitic M5076 tumor model of C57BL/6 mice and had no significant difference compared with that of doxorubicin HCl liposome injection (Doxil).     

注射用灯盏花素在7种注射液中的稳定性研究

目的:考察注射用灯盏花素与临床常用溶剂的配伍稳定性,为临床应用提供参考。方法:模拟临床用药情况,将注射用灯盏花素与5%葡萄糖注射液、0.9%氯化钠注射液、10%葡萄糖注射液、5%葡萄糖氯化钠注射液、极化液(含Na+、K+、Ca2+)、果糖注射液、转化糖电解质7种常用溶剂配伍,放置0、1、2、4、8 h后考察配伍液的外观、pH值、不溶性微粒及吸收度的变化。结果:注射用灯盏花素与7种溶剂配伍后,吸收度、pH值无明显变化,但外观、不溶性微粒考察除与5%葡萄糖注射液、0.9%氯化钠注射液配伍后无改变外,另外5种注射液均存在着不同程度的变化。结论:注射用灯盏花素适宜与0.9%氯化钠注射液、5%葡萄糖注射液配伍,在8 h内基本稳定。     

灯盏花素与6种液体配伍时的稳定性观察

目的观察灯盏花素与6种液体配伍时的稳定性。方法将灯盏花素分别溶于0.9%氯化钠注射液、5%葡萄糖注射液、10%葡萄糖注射液、葡萄糖氯化钠注射液、10%转化糖注射液和果糖注射液,观察溶液物理变化并测定含量。结果灯盏花素与0.9%氯化钠注射液、5%葡萄糖注射液和10%葡萄糖注射液配伍比较稳定,澄明度、颜色和药物（灯盏花甲素和灯盏花乙素等混合物）含量均未发生任何变化;而与葡萄糖氯化钠注射液、10%转化糖注射液和果糖注射液配伍则出现乳黄色沉淀,其上清液中的药物含量则明显降低。结论灯盏花素与0.9%氯化钠注射液、5%葡萄糖注射液或10%葡萄糖注射液配伍时,药液稳定性比较好;与灯盏花素配合时还要考虑药液的pH值等因素。     

Characterization, biodistribution and targeting evaluation of breviscapine lipid emulsions following intravenous injection in mice

Breviscapine lipid emulsions were prepared by a high speed dispersion-homogenization method with optimal formulation and technological method. The proportion of liposomes in breviscapine lipid emulsions, an important character for determining the behavior of drug in vivo belongs to which carriers, was less than 5%. Loading breviscapine into lipid emulsions did increase the breviscapine concentrations in plasma, retarded the clearance, and exhibited the properties of sustained-release concluded by pharmacokinetic parameters: after bolus administration, the elimination phase (t(1/2(β))?=?99.535) of lipid emulsions was 5.4-times longer than that of Injectio Breviscapine. The AUC(0→∞) (14.453-times), k(10) (0.047-times), Cl(s) (0.147-times), and MRT(0→∞) (17.766-times) values also confirmed this trend. The amount of drug in every tissue increased at different levels after intravenous administration of breviscapine lipid emulsions compared with Injectio Breviscapine. The relative exposure value of breviscapine lipid emulsions for plasma and lungs were 29.59 and 5.81, respectively, indicating that the exposure of breviscapine to plasma and lungs was significantly increased by entrapment in lipid emulsions. Other targeting evaluation indexes also proved the superiority of lipid emulsions carrier to deliver drug to the targeting region of vascular and lung diseases therapy.     

Preparation,characterization, and biodistribution of breviscapine proliposomes in heart

Breviscapine proliposomes were prepared by ethanol injection–homogenization–lyophilization method. On contact with 5% glucose, the proliposomes were rapidly converted into a liposomal dispersion, in which a certain amount of breviscapine was entrapped by the liposomes. The entrapment efficiency measured by reverse dialysis method was 77.89?±?0.28%. The particle size, polydispersity index, and zeta potential of breviscapine liposomes were 504.83?±?52.88?nm (by intensity), 0.17?±?0.02, and ?(20.31?±?1.03) mV, respectively (mean ± SD, n = 3). In mimic-biomembrane model experiment, breviscapine was distributed not only to n-octanol and buffer phase but also to interfacial phase. After bolus administration, the elimination phase (t_1/2(β) = 66.386) of liposomal formulation in plasma was 4.8 times longer than that of solution formulation (t_1/2(β) = 13.695). The AUC and MRT values of liposomal formulation in heart were increased more than 11.7- and 3.2-fold versus solution formulation, respectively. These results were all beneficial to heart disease therapy.     

Polyethylene glycol-coated liposomes for oral delivery of recombinant human epidermal growth factor

The present study was to investigate the feasibility of oral delivery of recombinant human epidermal growth factor (rhEGF). Polyethylene glycol (PEG)-coated liposomes containing rhEGF was prepared and evaluated for their stability and permeability in Caco-2 cells. In the animal study, we also determined plasma concentration and gastric ulcer healing effect after oral administration of rhEGF liposomes or the solution. Encapsulation of rhEGF into liposomes, suppressed the degradation in Caco-2 cell homogenate compared with the solution. The flux of rhEGF from dipalmitoylphosphatidylcholine (DPPC) liposome across Caco-2 cell monolayer from the apical to basolateral side was three times greater than that from phosphatidylcholine (PC) liposome or the solution. After oral administration of rhEGF liposomes or the solution in rats, the area under the concentration-time curve (AUC) of rhEGF increased 1.7- and 2.5-fold for PC and DPPC liposomes, respectively. The gastric ulcer healing effect was significantly increased in DPPC liposome compared with PC liposome and the solution. The enhanced curative ratio of rhEGF encapsulated into DPPC liposome may be due to the resistance to enzyme degradation, higher permeability and increased plasma AUC. Therefore, PEG-coated liposomes containing rhEGF could be used as an oral delivery formulation with enhanced encapsulation efficiency.     

Multivesicular liposome formulation for the sustained delivery of breviscapine

Breviscapine, a well-known bioactive flavonoid ingredient extracted from the traditional Chinese medicine, has been extensively used in clinic to treat ischemic cerebrovascular and cardiovascular diseases in China. In order to prolong the duration of the drug in the circulation, reduce the frequency of injection administration and subsequently afford patient compliance, multivesicular liposome (MVL, namely DepoFoam) was utilized as a sustained-delivery system for breviscapine. In vitro release and in vivo pharmacokinetics of MVLs containing breviscapine (bre-MVLs) following intramuscular injection to rats were investigated compared with those of traditional liposomes containing breviscapine (bre-TLs). The drug durations both in vitro and in vivo were significantly prolonged for the bre-MVL, and that the drug release in vitro and the absorption in vivo showed a good linear correlation (R=0.9834), which provided an evidence for the suitability to select human plasma as the medium of drug release from MVLs in vitro. Drug release from bre-MVLs (triolein/tricaprylin, 10/0) in vitro extended a long period of 5-6 days, while the bre-TLs released 80% within only 4h. The mean residence time (MRT) obtained from the pharmacokinetics study of bre-MVL was about 16.6- and 5.04-fold longer than those of breviscapine solution (BS) and bre-TL, respectively. A duration in vivo for a period of 4-5 days was fulfilled for bre-MVL. In conclusion, MVL can be successfully used as a sustained delivery system of breviscapine.     

Co-encapsulation of isoniazid and rifampicin in liposomes and characterization of liposomes by derivative spectroscopy

Taking into consideration the benefits of the combined therapy of isoniazid (INH) and rifampicin (RIF), this study focused on co-encapsulation of INH and RIF in the same liposome formulation. INH was incorporated in the aqueous phase and RIF in the lipid layer. Liposomes containing either INH or RIF were also prepared. All liposome formulations were compared for their loading capacity, encapsulation percentage and release properties. Drug amounts in the liposomes were estimated using peak-to-peak first-order derivative UV spectroscopy. Among the liposome formulations DPPC:chol liposomes showed the highest loading capacity (106.70 +/- 0.12 for INH and 18.17 +/- 0.06 (x 10(-3)) for RIF) and encapsulation percentage (73.84 +/- 0.78 for INH and 81.53 +/- 2.06 for RIF) compared to EPC:chol liposomes (loading capacity 93.36 +/- 0.58 for INH and 17.87 +/- 0.11 (x 10(-3)) for RIF; encapsulation percentage 64.61 +/- 0.51 for INH and 74.45 +/- 0.48 for RIF). Co-encapsulation of INH and RIF increased their individual encapsulation percentage and extended drug release compared to the formulations containing drug alone (Table 2). Results of this study support the conclusion that lipid and water soluble drugs can be successfully co-encapsulated in the same liposome formulation and also show that derivative UV spectroscopy is a sensitive method for direct and accurate quantification of these co-encapsulated drugs.     

超氧化物歧化酶脂质体在大鼠体内的药代动力学和组织分布

目的考察3种超氧化物歧化酶(SOD)脂质体静脉给药后在大鼠体内的药代动力学和组织分布。方法 用反相蒸发法制备SOD脂质体，采用黄嘌呤氧化酶法检测SOD活力，静脉注射给药后，测定大鼠血中SOD含量变化和不同组织中SOD含量变化。结果在血浆中，SOD水溶液、SOD普通脂质体、用DSPE-PEG2000修饰的SOD脂质体、用Tween 80修饰的SOD脂质体的半衰期分别为0.25，0.34，0.66和0.41 h；AUC分别为12.48，24.66，41.16和33.02 μg·h·mL^-1。与普通脂质体比较，经过DSPE-PEG和Tween 80修饰后的脂质体，使肝、脾中SOD的含量有不同程度的降低，脑中含量有所提高。结论3种SOD脂质体均可不同程度地延长SOD的血浆半衰期，并以用DSPE-PEG2000修饰的SOD脂质体效果最好。与普通脂质体相比，用Tween 80修饰的SOD脂质体可以提高进入脑中的SOD量，用DSPE-PEG2000修饰的SOD脂质体可以减少肝脾对SOD的摄取。     

双氯酚酸钠脂质体的制备及其眼部药代动力学

目的研究双氯酚酸钠脂质体的制备方法并考察其在家兔眼部的药代动力学特征。方法采用逆相蒸发法制备双氯酚酸钠正电荷脂质体。脂质体和滴眼液滴眼后家兔采用高效液相色谱法测定角膜前、角膜和房水中药物浓度。结果制得的脂质体平均粒径为226.5 nm，多分散度为0.214，ζ电位为+18.1 mV，经均匀设计优化处方，包封率可达到63%。0.1%双氯酚酸钠脂质体和滴眼液两种制剂家兔局部滴眼后的药代动力学研究显示，脂质体可延缓药物在角膜前的清除，增加角膜中药物的浓度，药物在房水中半衰期延长，以滴眼液为参比制剂，相对生物利用度为211%。结论双氯酚酸钠正电荷脂质体可以增加药物在角膜前的滞留时间，提高角膜渗透性及药物在眼部的生物利用度，减少滴眼次数。     

阿霉素的不同盐型对其脂质体体外药物泄漏和体内长循环的影响

目的探讨阿霉素不同盐型对脂质体体内外稳定性的影响。方法以薄膜分散-挤压法制备含有不同缓冲对的空白脂质体，用pH梯度和化学梯度法包载阿霉素，对其在脂质体内状态进行观察，测定了阿霉素脂质体理化性质；用透析法检测阿霉素脂质体在不同介质中的药物泄漏；用HPLC法研究不同盐型阿霉素脂质体在大鼠体内药代动力学行为。结果甘氨酸盐缓冲液、柠檬酸盐缓冲液和硫酸铵溶液作内水相制得的空白脂质体的平均粒径分别为(103±8)，(102±12)和(97±8) nm，zeta电位分别为(-21.3±0.5)，(-21.7±0.4)和(-20.9±0.7) mV，对阿霉素的包封率分别为47.8%，96.7%和98.6%。甘氨酸盐制得的脂质体体外泄漏最快，硫酸铵制得的脂质体泄漏最慢；甘氨酸盐缓冲液、柠檬酸盐缓冲液和硫酸铵溶液作内水相制得的阿霉素脂质体大鼠体内平均滞留时间分别为12.13，23.31和29.79 h。结论阿霉素在脂质体内水相中不同盐型影响其脂质体的体内外稳定性，以硫酸铵为内水相制得的阿霉素脂质体最稳定，其稳定次序与内水相中酸的强度有关，酸性越弱其脂质体稳定性越高。     

Effects of soybean-derived sterol and its glucoside mixtures added in dipalmitoylphosphatidylcholine liposomes on the blood circulation and hepatic cellular distribution in mice

The effects of a soybean-derived sterol mixture (SS) and their glucoside mixture (SG) in dipalmitoylphosphatidylcholine (DPPC) liposomes on blood circulation and hepatic distribution were investigated by measuring the leakage of calcein after intravenous administration to mice. Four kinds of liposomes were prepared: liposomes consisting only of DPPC (DPPC liposomes); and DPPC liposomes containing SS, cholesterol (Ch) or SG (molar ratio of DPPC/X = 7:2, X = SS, Ch, SG; SS, Ch and SG liposome), respectively. The area under the blood concentration-time curve (AUC) was greater in the order, SS liposomes > DPPC liposomes > SG liposomes, and the order is the same for lower membrane fluidity. Hepatic cellular distribution of SG liposomes 2 h after intravenous injection was significantly high compared with that of DPPC and SS liposomes. The results indicated that SS liposomes were stable in the blood circulation; however, SG liposomes were not stable and appeared to have an enhancing effect on hepatic uptake. This difference might indicate that hepatic accumulation is primarily governed by the glucose group of SG.     

盐酸多柔比星脂质体的制备及体外质量评价

目的：制备盐酸多柔比星脂质体并进行体外质量评价,以期实现自制脂质体质量与市售盐酸多柔比星脂质体注射液Doxil一致,并为其生物体内等效及产业化提供研究基础。方法：采用乙醇注入法结合硫酸铵梯度法制备盐酸多柔比星脂质体,以包封率为评价指标通过单因素筛选和正交试验优化制备工艺,以市售Doxil为参比制剂,对比最优工艺制得的脂质体与市售Doxil的微观结构、粒径大小及分布、Zeta电位、相变温度、包封率等理化指标,考察最优工艺制得的脂质体与市售Doxil在加速条件的体外释放及储存条件下稳定性情况。结果：自制盐酸多柔比星脂质体最优制备工艺为高速剪切速率13 000 r·min^-1,挤出3次,载药孵育温度65℃,载药孵育时间60 min,最优工艺制得的脂质体与市售Doxil外观均为椭圆形,平均粒径分别为（90.81±0.58） nm （n=3）和（89.05±0.66） nm （n=3）,分布较为均匀,Zeta电位分别为（-41.9±1.8） mV （n=3）和（-44.9±4.2） mV （n=3）,相变温度范围相同,包封率分别为98.0%和97.9%,体外释放较为一致,稳定性好。结论：采用最优工艺制备的盐酸多柔比星脂质体制备工艺可行,与市售Doxil相比,理化指标及体外释放无明显差异,自制脂质体体外质量良好,符合实验预期。     

Pharmacokinetics of His-tag recombinant human endostatin in Rhesus monkeys

AIM: To study the pharmacokinetics and accumulation of an Escherichia coli expressed His-tag fused recombinant human endostatin (rh-endostatin) in Rhesus monkeys. METHODS: Rh-endostatin was iv or sc injected in Rhesus monkeys, and the rh-endostatin concentration in serum samples was determined by an enzyme immunoassay (EIA) method. The serum drug concentration-time data were analyzed by compartmental analysis using the practical pharmacokinetic program 3p97. RESULTS: Following iv administration at a dose rate of 1.5, 4.5, and 13.5 mg/kg in rhesus monkeys, the concentration-time curves of rh-endostatin were best fitted to a three-compartment open model. AUC(0-infinity) linearly increased with dose, while Cls exhibited no significant difference among different dose groups. The terminal half-lives (lambda3) were 8+/-8, 3.1+/-1.4, and 20+/-14 h, respectively. After sc administration at a dose rate of 1.5 mg/kg, the concentration-time curve was best fitted to a two-compartment open model, with a terminal half-life (T(1/2beta)) of 8+/-3 h. Bioavailability following sc injection was approximately 70%+/-3%. After consecutive iv injection of rh-endostatin at a dose rate of 1.5 mg.kg(-1).d(-1) for 7 d, the AUC(0-24 h) substantially increased from 22+/-13 mg.h.L(-1) (d 1) to 50+/-29 mg.h.L(-1) (d 7), with an accumulation factor of 2.3+/-0.6 (P < 0.05). CONCLUSION: The pharmacokinetic behavior of rh-endostatin in Rhesus monkeys complies with linear kinetics within the examined dose range. It tends to be accumulated in bodies after repeated administration at a dose level of 1.5 mg.kg(-1).d(-1) for more than 7 consecutive days.     

灯盏花素及其β-环糊精包合物在大鼠体内的药代动力学

目的建立测定大鼠血浆中灯盏乙素浓度的反相高效液相色谱法，研究灯盏花素及其β-环糊精包合物(灯盏花素-β-CD)大鼠灌胃后体内药代动力学行为。方法以甲醇-水-醋酸盐缓冲液为流动相，Shim-pack C₁₈为固定相；12只大鼠随机均分为2组，分别灌胃灯盏花素及其包合物后，检测血浆药物浓度。药时数据采用3P97药代计算程序处理。结果线性范围10-400 ng·mL^-1，方法回收率95.32%-98.81%；灯盏花素和包合物的C_max分别为(154±18) ng·mL^-1和(328±31) ng·mL^-1；AUC_0-12h分别为(710±126) ng·h·mL^-1和(1 093±200)ng·h·mL^-1，经t检验两者有极显著性差异(P<0.01)。结论该法准确、灵敏，适用于灯盏乙素血浆浓度的测定；制备的灯盏花素包合物与灯盏花素相比吸收显著增加。     

The effect of PEG coating on in vitro cytotoxicity and in vivo disposition of topotecan loaded liposomes in rats

Amphoteric drugs encapsulated in PEGylated liposomes may not show superior therapeutic antitumor activity due to increased leakage rate of these drugs in presence of PEG-lipids. In order to investigate the effect of PEG coating on in vitro and in vivo characteristics of topotecan loaded liposomes, an amphoteric anticancer drug, PEGylated and conventional liposomes were prepared by lipid film hydration method. Various properties of the prepared nanoliposomes such as encapsulation efficiency, size, zeta potential, physical stability as well as the chemical stability of lactone form of topotecan, cytotoxicity and topotecan pharmacokinetics were evaluated. In vitro cytotoxic activity was evaluated on murine Lewis lung carcinoma (LLC) and human mammary adenocarcinoma (BT20) cells. Pharmacokinetic was evaluated in Wistar rats after i.v. injection of topotecan, formulated in PBS pH 7.4 or in conventional or in PEGylated liposomes. The conventional liposome (CL) formulation was composed of DSPC/cholesterol/DSPG (molar ratio; 7:7:3), while for PEGylated liposome the composition was DSPC/cholesterol/DSPG/DSPE-PEG(2000) (molar ratio; 7:7:3:1.28). The size of both liposomes was around 100 nm with polydispersity index of about 0.1. In comparison with free drug, liposomal topotecan showed more stability for topotecan lactone form in vitro. Compared to free topotecan, PEGylated and conventional liposomes improved cytotoxic effect of topotecan against the two cancer cell line studied. The results of pharmacokinetic studies in rats showed that both CL and PEGylated liposomal formulations increased the concentration of total topotecan in plasma, however, initial concentration and the values of AUC, MRT and t(1/2 beta) were much higher (P<0.001) for PEGylated liposomal drug than for conventional one or free drug. PEGylated liposome resulted in a 52-fold and 2-fold increases in AUC(0-infinity) compared with that of free topotecan and CL, respectively. These results indicated that PEG modified liposome might be an effective carrier for topotecan.     

A Physiologically Based Pharmacokinetic (PBPK) Model for Predicting the Efficacy of Drug Overdose Treatment With Liposomes in Man

Physiologically based pharmacokinetic (PBPK) models were developed for design and optimization of liposome therapy for treatment of overdoses of tricyclic antidepressants and local anesthetics. In vitro drug-binding data for pegylated, anionic liposomes and published mechanistic equations for partition coefficients were used to develop the models. The models were proven reliable through comparisons to intravenous data. The liposomes were predicted to be highly effective at treating amitriptyline overdoses, with reductions in the area under the concentration versus time curves (AUC) of 64% for the heart and brain. Peak heart and brain drug concentrations were predicted to drop by 20%. Bupivacaine AUC and peak concentration reductions were lower at 15.4% and 17.3%, respectively, for the heart and brain. The predicted pharmacokinetic profiles following liposome administration agreed well with data from clinical studies where protein fragments were administered to patients for overdose treatment. Published data on local cardiac function were used to relate the predicted concentrations in the body to local pharmacodynamic effects in the heart. While the results offer encouragement for future liposome therapies geared toward overdose, it is imperative to point out that animal experiments and phase I clinical trials are the next steps to ensuring the efficacy of the treatment.     

Enhanced Tumor Targeting of Doxorubicin by Ganglioside GMl-bearing Long-circulating Liposomes

Abstract

Doxorubicin (DXR) was encapsulated in long-circulating liposomes, composed of ganglioside GM1 (GM1)/distearoylphosphatidylcholine (DSPC)/cholesterol (CH) (0.13:1:1 in molar ratio) and sized to approximately 100 nm in mean diameter, with 98% entrapping efficiency by the transmembrane pH gradient method. Free DXR, DXR-DSPC/CH and DXR-GM1/DSPC/CH liposomes were injected intravenously into Colon 26 tumor-bearing Balb/c mice via the tail vein at a dose of 5.0 mg DXR/kg. DXR-GM1/DSPC/CH liposomes gave a higher blood level of the drug than did DXR-DSPC/CH liposomes or free DXR up to 24 hours after injection, and the area under the blood concentration-time curve (AUC) for DXR-GM1/DSPC/CH liposomes was 1.5 or 526 times higher than that for DXR-DSPC/CH liposomes or free DXR, respectively. DXR-GM1/DSPC/CH liposomes gave a decreased DXR concentration in the reticuloendothelial system (RES) of the liver and the spleen. Both liposomal formulations effectively reduced the DXR concentration in the heart as compared with that in the case of free DXR. At 6 hours after i.v. injection, DXR-GM1/DSPC/CH liposomes provided an approximately 3.3- or 9-fold higher peak DXR level in the tumor as compared with DXR-DSPC/CH liposomes or the free drug, respectively. These high tumor levels of DXR appear to reflect the prolonged residence time of the liposomes. The results suggest that encapsulation of DXR in GM1-bearing long-circulating liposomes will be useful for cancer chemotherapy.