Dexamethasone incorporating liposomes: effect of lipid composition on drug trapping efficiency and vesicle stability

Effect of lipid composition on encapsulation and stability of dexamethasone (DXM) incorporating multilamellar vesicles (MLV) is studied. MLVs composed of phosphatidylcholine (PC) or distearoyl-glycero-PC (DSPC), with or without cholesterol (Chol), are prepared and the release of DXM during vesicle incubation in buffer or plasma proteins is evaluated. Incorporation of DXM is slightly higher in DSPC liposomes compared with PC, whereas the drug is displaced from liposomes, as the Chol content of liposome membranes increases. Plain lipid and Chol-containing liposomes lose similar fractions of vesicle-incorporated DXM during incubation in buffer or serum, whereas DXM release kinetics are similar (for each liposome type studied), implying that drug release is due mainly to dilution of liposome dispersions that leads to repartitioning of DXM.     

Encapsulation, Stability, and In Vitro Release Characteristics of Liposomal Formulations of Stavudine (D4T)

The objective of this study was to examine the encapsulation of stavudine (d4T), an approved drug for AIDS treatment, in liposomes composed of various lipids and the in vitro release characteristics, and to evaluate the stability. The reverse phase evaporation method was used to prepare liposomes and the effect of cholesterol on drug encapsulation was studied by adding different amounts of cholesterol to a constant amount of lipid. The effect of charge of the lipid bilayer on drug encapsulation was also studied. Stearylamine or dicetylphosphate (10 mol%) were used to induce positive or negative charges, respectively. The particle size of the liposomes was measured using dynamiclightscattering. Stabilitystudies were performed by storing formulations at 4, 25, and 37 C for 12 weeks, and then subjecting them to alternate heat-cool cycles and simulated transportation conditions. Encapsulation of stavudine was found to be maximum (48%) in DSPC liposomes containing equimolar amounts of cholesterol. Encapsulation generally increased with increasing amounts of cholesterol, and also with the incorporation of both positive and negative charge. In vitro release was found to be biphasic, the release controlled by the dialysis membrane and the lipid bilayer. The release of the drug was inhibited in the presence of charge (30%), compared to neutral liposomes. Particle size distribution ranged from 0.6 mu m to 1.4 mu m and was polydisperse. Liposomes were stable with respect to the amount to drug retained for a period of 4 weeks. Beyond 4 weeks, there was a leakage of entrapped drug independent of the temperature of storage. An increase in particle size during storage was observed in the case of neutral but not charged vesicles. A high degree of encapsulation of stavudine in liposomes is feasible by reverse-phase evaporation. Liposomal formulations may be beneficial in alleviating the longterm side effects of stavudine and enhancing in vivo cellular uptake in HIV therapy.     

聚乙二醇对盐酸伊立替康脂质体体外释放及在不同稀释介质中稳定性的影响

目的:考察不同聚乙二醇含量对盐酸伊立替康脂质体体外释放特性及在不同稀释介质中稳定性的影响。方法:采用乙二胺四乙酸铵梯度法,以聚乙二醇2000含量分别为0、8、14、20、26 mg/ml的聚乙二醇2000-二硬脂酰磷脂酰乙醇胺(m PEG2000-DSPE)制备盐酸伊立替康脂质体,测定其包封率和粒径,评价其体外24 h内的累积释放度和在生理氯化钠溶液与5%葡萄糖注射液中的稳定性。结果:随着m PEG2000-DSPE含量的增加,盐酸伊立替康脂质体体外24 h累积释放度逐渐减小;以生理氯化钠溶液及5%葡萄糖注射液稀释后,随着m PEG2000-DSPE含量的增加,盐酸伊立替康脂质体的包封率和粒径变化均减小;当聚乙二醇2000质量浓度增加至20、26 mg/ml时,脂质体包封率和粒径基本不再变化。结论:m PEG2000-DSPE的加入可减慢盐酸伊立替康脂质体的体外释放,提高其在不同稀释介质中的稳定性。     

细辛脑注射液与地塞米松磷酸钠配伍稳定性研究

目的：考察细辛脑注射液与地塞米松磷酸钠注射液在50g.L-1葡萄糖中的稳定性。方法：观察配伍液的外观、测定不溶性微粒、pH值,采用HPLC法测定细辛脑的含量。结果：配伍液在室温时4h内无明显外观、pH值的变化,含量在90%以上,不溶性微粒符合规定。结论：细辛脑与地塞米松磷酸钠注射液配伍室温4h内基本稳定。     

2-甲氧基雌二醇脂质体的质量评价

目的:对2-甲氧基雌二醇(2-ME)脂质体进行质量评价. 方法:用乙醚注入法制备2-ME脂质体,与原料药相比,体外释药情况的考察. 并从粒径包封率两个方面进行稳定性考察. 结果:体外释药试验表明,与原料药相比,脂质体无突释现象且持续释药, 4℃存放两周稳定性较好. 结论:用乙醚注入法制备的2-ME脂质体质量稳定,可为2-ME的临床应用提供一种新剂型.     

地塞米松磷酸钠与青霉素G注射剂配伍稳定性考察

目的 探讨青霉素G钠和地塞米松磷酸钠注射液（DXM）的配伍稳定性. 方法 以青霉素G钠 320万U和不同剂量DXM在5%葡萄糖（5%GS）及0.9%氯化钠注射液（NS）中配伍,室温6 h内观察外观、测pH值、高效液相色谱法测色谱峰高、紫外分光光度法测吸光度（A值）. 结果 青霉素G钠和DXM两药配伍液6 h内外观澄明,配伍液pH值随DXM剂量增加而上升,并接近中性;紫外分光光度法测定,6 h内吸收曲线未明显改变,最大吸收波长处A值未明显变化; DXM对青霉素G钠色谱峰未见明显影响,在3 h 后有轻度稳定作用;DXM 40 μg&;#8226;mL-1对提高青霉素G钠稳定性最强. 结论 DXM与青霉素G钠在5%GS或NS中配伍,配伍无禁忌,有轻度稳定作用.     

盐酸雷莫司琼注射液与地塞米松磷酸钠注射液配伍稳定性考察

目的:考察盐酸雷莫司琼注射液与地塞米松磷酸钠注射液配伍后的稳定性。方法:建立高效液相色谱法测定在4、25、37℃避光和光照条件下该配伍液(0.9%氯化钠注射液为溶媒)中雷莫司琼的含量;另对该配伍液的pH值、不溶性微粒进行考察,并做外观检查。结果:盐酸雷莫司琼注射液与地塞米松磷酸钠注射液配伍后,避光条件下48 h内配伍液的pH值、主药百分含量相对0 h均无明显变化,所有条件下外观检查均合格,不溶性微粒均符合《中国药典》(2010年版)规定;而在光照条件下,随着温度的升高,放置时间的延长,配伍液的pH值、主药含量均有所下降,不溶性微粒则无变化。结论:盐酸雷莫司琼注射液与地塞米松磷酸钠注射液在0.9%氯化钠注射液中配伍,于避光条件下可稳定共存,且光照是影响其稳定性的主要因素。     

表面双膦酸盐修饰的丹参素脂质体稳定性及骨靶向性研究

摘 要 目的： 制备骨靶向丹参素脂质体并研究其理化性质。方法: 采用逆向蒸发法制备靶向性脂质体。透射电镜观察脂质体的形态,HPLC测定脂质体中丹参素含量,考察骨靶向脂质体在室温下的稳定性,透析法考察脂质体在血浆存在条件下的体外释放度,并采用羟磷灰石晶体吸附试验考察目标物的骨靶向性。结果: 表面修饰制备的靶向载药脂质体呈圆球形,室温下为稳定的乳白色混悬液。5天内测得的包封率为31.1%,渗漏率为20.5%。在血浆条件下脂质体有明显的缓释作用,24 h累计释放量为84.6%。表面修饰的脂质体有骨靶向性,羟基磷灰石吸附量随靶向物含量的增加而增加。结论:表面修饰的丹参素脂质体具有骨靶向性,且缓释作用明显。     

地塞米松磷酸钠滴眼液的稳定性考察

目的:考察地塞米松磷酸钠滴眼液的稳定性,预测其有效期。方法:采用高效液相色谱法测定地塞米松磷酸钠滴眼液中地塞米松磷酸钠的含量,以初匀速法预测其稳定性。结果:地塞米松磷酸钠检测浓度的线性范围为18~70μg.mL-1(r=0.999 9),平均回收率为99.74%,RSD=0.37%;滴眼液随温度的升高以及存放时间延长其含量下降,但pH变化不明显。计算得25℃时其有效期为70d,4℃冷藏其有效期可延长至438d。结论:本品4℃存放稳定性较好。     

地塞米松磷酸钠注射液和盐酸利多卡因凝胶混合物稳定性考察

目的:考察地塞米松磷酸钠注射液和利多卡因凝胶混合后14天内的稳定性。方法:利用高效液相色谱法同时测定地塞米松磷酸钠和盐酸利多卡因,采用SUPELCO C18色谱柱(5μm,4.6mm×150mm),流动相为甲醇-乙腈-水(55:5:40),流速1mL/min,紫外检测波长为240nm,柱温35℃,进样量20μL。结果:在上述色谱条件下,盐酸利多卡因在2min左右出峰,地塞米松磷酸钠在6min左右出峰,两峰分离度良好。混合14d内两峰峰面积数值基本稳定,且无新的紫外吸收峰形成。结论:地塞米松磷酸钠注射液和利多卡因凝胶混合后14d内性质稳定,含量基本不变,且没有新的物质生成,可联合使用。     

Targeting Efficiency of Galactosylated Liposomes to Hepatocytes in Vivo: Effect of Lipid Composition

Purpose. To investigate the effects of the lipid composition of galactosylated liposomes on their targeted delivery to hepatocytes. Methods. Several types of liposomes with a particle size of about 90 nm were prepared using distearoyl-L-phosphatidylcholine (DSPC), cholesterol (Chol) and cholesten-5-yloxy-N-(4-((1-imino-2-D-thiogalactosylethyl)amino)butyl)formamide (Gal-C4-Chol), and labeled with [³H]cholesterol hexadecyl ether. Their tissue disposition was investigated in mice following intravenous injection. The binding and internalization characteristics were also studied in HepG2 cells. Results. Compared with [³H]DSPC/Chol (60:40) liposomes, [³H]D-SPC/Chol/Gal-C4-Chol (60:35:5) liposomes exhibit extensive hepatic uptake. Separation of the liver cells showed that galactosylated liposomes are preferentially taken up by hepatocytes, whereas those lacking Gal-C4-Chol distribute equally to hepatocytes and nonparenchymal cells (NPC). Increasing the molar ratio of DSPC to 90% resulted in enhanced NPC uptake of both liposomes, suggesting their uptake via a mechanism other than asialoglycoprotein receptors. DSPC/Chol/Gal-C4-Chol (60:35:5) and DSPC/Chol/Gal-C4-Chol (90:5:5) liposomes exhibited similar binding to the surface of HepG2 cells, but the former were taken up faster by the cells. Conclusions. The recognition of galactosylated liposomes by the asialoglycoprotein receptors is dependent on the lipid composition. Cholesterol-rich galactosylated liposomes, exhibiting less non-specific interaction and greater receptor-mediated uptake, are better for targeting drugs to hepatocytes in vivo.     

The Effect of Different Lipid Components on the In Vitro Stability and Release Kinetics of Liposome Formulations

Liposomes are colloidal carriers that form when certain (phospho)lipid molecules are hydrated in an aqueous media with some energy input. The ideal liposome formulation with optimum stability will improve drug delivery by decreasing the required dose and increasing the efficacy of the entrapped drug at the target organ or tissue. The most important parameter of interest in this article was to compare the efficacy of three different liposomes formulated with DSPC, DMPC, and DPPC, all saturated neutral phospholipids with different acyl chain lengths and transition temperatures. DMPC has a phase transition temperature (Tc) below 37°C, whereas the other two phospholipids possess Tcs above the physiological temperature. These lipids were then added to a cholesterol concentration of 21% to optimize the stability of the vesicles. The liposomes were prepared by a sonication and incubated in phosphate buffered saline (PBS) at 4°C and 37°C. The encapsulation efficiency, initial size, and drug retention of the vesicles were tested over a 48-hr period employing radiolabeled inulin as a model drug. The phase transition temperature of liposomes, which depends on the Tc of the constituent lipids, was an important factor in liposome stability. Of all the liposomes tested, the greatest encapsulation efficiency was found for the DSPC liposomes (2.95%) that also had the greatest drug retention over 48 hr at both 4°C (87.1 ± 6.8%) and 37°C (85.2 ± 10.1%), none of these values being significantly different from time zero. The lowest drug retention was found for DMPC liposomes for which a significant difference in drug retention was seen after only 15 min at both 4°C (47.3 ± 6.9%) and 37°C (53.8 ± 4.3%). The DPPC liposomes showed a significant difference in drug retention after 3 hr at 4°C (62.1 ± 8.2%) and after 24 hr at 37°C (60.8 ± 8.9%). Following the initial drop at certain time intervals a plateau was reached for all of the liposome formulations after which no significant difference in drug retention was observed. In conclusion, liposomes with higher transition temperatures appear to be more stable in PBS either at 4°C or 37°C, indicating that the increase in acyl chain length (and therefore transition temperature) is directly proportional to stability.     

Enhancement of Gene Expression Efficiency Using Cationic Liposomes on Ovarian Cancer Cells

We performed transfection using cationic liposome. According to the gene expression level, lined cells were divided into two groups, high and low. Introduced gene was monitored with a confocal laser-scanning microscope. The percentages of the cells introduced gene reached more than 90% in all line. Then, introduced gene was stable in high group, while in low group, it significantly decreased. With lysosomotrophic agents, gene expression efficiency was significantly reduced. With colchicine, gene expression efficiency did not change in high group, but was significantly elevated in low group. A method of liposomal transfection could be effective, particularly in low group.     

甲磺酸多拉司琼与地塞米松磷酸钠在两种输液中的配伍稳定性考察

目的：考察甲磺酸多拉司琼与地塞米松磷酸钠在两种输液中的配伍稳定性。方法：模拟临床操作,在室内室温（25℃）不避光环境下,临床常用量甲磺酸多拉司琼与地塞米松磷酸钠分别在5%葡萄糖注射液（5%GS）和0.9%氯化钠注射液（NS）中配伍,在0 h（配制后5 min内）、3、6、24 h对配伍液的物理稳定性（外观、不溶性微粒）、化学稳定性（pH值、浓度）进行考察。结果：配伍液在24 h内保持无色、澄清,未见气泡、絮状物和沉淀产生,不溶性微粒、pH值与配伍液中两药浓度变化符合配伍要求,且色谱图均未发现异常色谱峰。结论：在室内室温（25℃）不避光时,甲磺酸多拉司琼注射液和注射用地塞米松磷酸钠于100 mL 5%GS或0.9%NS中,24 h内配伍稳定。     

Stability of Liposomal Formulations in Physiological Conditions for Oral Drug Delivery

The stability of liposomal formulations is a key issue in drug delivery. Liposomes made of egg phosphatidylcholine (EPC), cholesterol (Chol), sphingomyelin (SM), and gangliosides (GM1 and GM type III) were incubated in different media to determine their stability. Mixtures containing GM1 or GM type III were found to be the most stable, and both showed similar stability trends in plasma at 37°C. EPC/Chol was the most susceptible to lysis in plasma. In acid media (pH 2), the highest stability corresponded to EPC/Chol, whereas in bile and pancreatin, liposomes with GM1 and GM type III were more stable than those containing SM. This study suggests that among the formulations used as oral drug carriers, those containing GM1 and GM type III have higher possibilities of surviving through the gastrointestinal tract.     

兰索拉唑脂质体的制备及其药剂学性质考察

目的:研究兰索拉唑阳离子脂质体的制备方法并考察其药剂学性质。方法:采用正交设计筛选处方,乙醇注入法制备兰索拉唑脂质体;超滤法测定其包封率;用透射电镜观察脂质体的外观形态,并用粒径分析仪和Zeta电位仪分别测定脂质体的粒径和Zeta电位;进一步考察脂质体的释放规律。结果:所得脂质体包封率约为(80±1.23)%;形态为粒径均匀的球形和类球形,粒径为(184±21)nm,Zeta电位为(36.1±5)mV;脂质体的体外释放符合一级方程;具有较好的稳定性。结论:优选得到的脂质体处方和制备工艺合理、稳定,其体外释放具有缓释特点。     

叶酸介导的多西他赛脂质体制备、质量控制及稳定性研究

摘 要 目的： 采用几种不同工艺制备叶酸介导的多西他赛脂质体,建立其质量控制方法并考察其稳定性。方法: 将氢化大豆磷脂酰胆碱 (HSPC)、叶酸 聚乙二醇2000 磷脂酰乙醇胺 (FA PEG2000 DSPE)及多西他赛以100∶5∶8的比例分别采用3种不同工艺制备脂质体。采用低速离心法测定包封率,动态光散射法测定粒度分布,GC法测定有机溶剂残留。结果: 脂质体平均粒径为(155 ± 10) nm,多项分散系数 (PdI)均小于0.20;脂质体包封率均大于95.0%;所制得样品于(25±2)℃条件下放置6个月,各项考察指标均未发生明显变化。结论:采用制备工艺3所制得的样品具有较高的药脂比,该制备工艺可行,质量可控,稳定性良好。体外释放曲线表明脂质体有缓释、靶向及长效作用。     

Liposomes with tretinoin: a physical and chemical evaluation

The comedolytic activity of tretinoin, incorporated in liposomes, is five to ten times higher compared to the conventional preparations and also the local tolerability is much better. This implies the big interest of a study on tretinoin in liposomes. First, the encapsulation capacity of tretinoin in the liposomes was determined. Therefore, a series of liposomes was prepared with different concentrations of tretinoin (1–6 mg/ml buffer) and lipids (100–300 mg/ml buffer) (egg phosphatidyl choline/cholesterol) with buffers pH=5 and 7. These series of liposomes were evaluated microscopically on the presence of tretinoin crystals outside the liposomes. The highest incorporation capacity was obtained using 2 mg of tretinoin and 300 mg of lipids per milliliter of buffer pH=5. The chemical stability of tretinoin in the liposomes, evaluated during 1 year, revealed no remarkable loss in tretinoin content, even when stored at 25 °C. The photo-degradation of tretinoin in the liposomes was about two times slower than in castor oil, but tretinoin degraded to ≈25% of its initial content. The chemical evaluation of the lipid fraction showed no oxidative degradation of the polyunsaturated fatty acids in EPC because the determined concentration of conjugated dienes and hydroperoxides, two oxidative degradation products, was <1%, which is negligible. Finally, the in-vitro release of tretinoin from the liposomes, evaluated with a dialysis technique, was very low, but this is not a problem for topical use.     

双氯芬酸钠脂质体的制备及包封率测定

目的:制备双氯芬酸钠脂质体并测定其包封率。方法:以pH梯度法制备脂质体,透射电子显微镜考察其形态与粒径;采用高效液相色谱法测定双氯芬酸钠的包封率。结果:制备的脂质体粒径大小均匀,粒径范围为150～175nm;双氯芬酸钠检测浓度的线性范围为0.01～1mg·mL-1(r=0.9990,n=6),平均回收率为100.05%(RSD=1.21%,n=6);包封率最高可达85.8%,最低52.4%。结论:本方法可制备得到包封率较高的双氯芬酸钠脂质体。     

HPLC 法测定冰片-葛根素脂质体中葛根素的含量和包封率

目的：建立冰片-葛根素脂质体中葛根素含量及包封率测定方法.方法：采用薄膜分散法制备冰片-葛根素脂质体,葡聚糖凝胶柱层析法分离脂质体和游离药物,采用高效液相色谱法测定脂质体中葛根素的含量和包封率.结果：葛根素在8～160 μg·ml^-1范围内线性关系良好（r=0.999 8） ;柱层析法可有效分离药物,分离游离药物的柱回收率为99.32%（RSD=1.16%,n=9）,加样回收率为98.56%（RSD=1.23%,n=9）.3批样品的平均包封率为62.35%,65.41%,63.18%（n=3）.结论：该方法准确、灵敏,可用于冰片-葛根素脂质体中葛根素含量及包封率的测定.