脂质体作为抗肿瘤药物载体的应用研究

目前，应用脂质体作为抗肿瘤药物载体已成为趋势。脂质体可明显提高抗肿瘤药物的靶向性，延长药物的作用时间，降低药物毒性。作者对国内外普通脂质体和修饰脂质体（包括长循环脂质体、免疫脂质体、温度敏感脂质体和pH敏感脂质体）的相关文献进行了综述。结果表明，脂质体是抗肿瘤药物的理想载体，在肿瘤治疗中有着广阔的应用前景。     

紫杉醇长循环脂质体及其抗肿瘤作用的研究

目的：探讨紫杉醇长循环脂质体（PSL）的急性毒性、抗肿瘤作用和稳定性。方法：制备PSL,其中含有聚乙二醇-二硬脂酰基磷脂酰乙醇胺（PEG-DSPE）和油酸。PEG-DSPE用于延长脂质体的血液循环时间,油酸用于降低脂质体的粒度。利用激光粒度/Zeta电位测定仪和Sephadex（350色谱柱,观察和测定了PSL的粒度分布、Zeta电位和包封率。在冷藏（7℃）避光条件下保存1年,观察其理化性质的改变。结果：PsL粒径为（138．6±4．6）nm,Zeta电位为（-31．6±7．9）mv,包封率可达（97．8＋2．6）％（n=3）。静脉注射后,与游离紫杉醇相比。长循环脂质体显著提高了紫杉醇的抗肿瘤作用,同时显著减轻了紫杉醇的急性毒性。在本试验条件下,保存1年,粒度、包封率几乎无改变,但紫杉醇含量下降8．2％。结论：PSL包封率高、粒度小,有可能成为一种较好的抗肿瘤药物。     

长循环脂质体的研究进展

脂质体的稳定性脂质体的物理、化学和生物学稳定性三个方面。其中生物学稳定性是脂质体在生物样品内保持长循环的关键,制备长循环脂质体是实现脂质体许多性质的前提和基础。本文从脂质体的物理、化学特性,膜材组成及构造等几个方面综述了制备长循环脂质体的基本原理,制备手段和方法。     

热敏脂质体的研究进展

综述以二棕榈酰磷脂酰胆碱（DPPC）等为主要膜材的常规热敏脂质体以及磁性热敏脂质体、长循环热敏脂质体、多聚物热敏脂质体、热敏免疫脂质体的研究进展。以热敏脂质体为载体包埋化疗药物,可结合热疗的优势和靶向给药的特点,提高治疗靶向性,降低全身毒性,增强抗肿瘤疗效。     

依托泊苷长循环热敏前体脂质体的制备工艺研究

目的:对依托泊苷(Etoposide,VP-16)长循环热敏前体脂质体的制备工艺进行研究,并对该制备工艺进行方法学及制剂质量考察。方法:应用薄膜分散法制成VP-16长循环热敏脂质体,进一步借助冷冻干燥技术进行依托泊苷长循环热敏前体脂质体的制备;采用zeta电势测定仪及HPLC等技术进行方法学考察,主要包括脂质体的包封率、粒径、载药量、电位、释放度、稳定性。结果:VP-16长循环热敏前体脂质体水合形成长循环热敏脂质体,粒径为(105.2±3.4)nm,Zeta电位为(-11.9±1.7)m V,包封率可达96.8%;该脂质体在相变温度42℃下药物释放达到96%以上。结论:VP-16长循环热敏前体脂质体的制备工艺稳定,脂质体载药量大,包封率高;药物含量及包封率的测定方法简单、快速而准确,因而,该研究可为VP-16开发成静脉注射用新制剂提供数据支持。     

脂质体载药系统与抗肿瘤药物

目的:介绍脂质体载药系统在抗肿瘤药物治疗中的应用.方法:采用文献综述方法,主要介绍普通脂质体和一些经过修饰后的脂质体作为药物载体的研究情况.结果:脂质体作为抗肿瘤药物的载体是可行的,可显著降低抗肿瘤药物的毒副作用,增加血药浓度并延长作用时间,还可明显提高抗肿瘤药物作用的靶向性.结论:脂质体是抗肿瘤药物的理想载体,在抗肿瘤治疗中有广泛的应用前景.     

薄膜分散法制备白藜芦醇长循环热敏前体脂质体及其表征研究

目的:对白藜芦醇长循环热敏前体脂质体制备的研究以及对其性质进行分析。方法:先用薄膜分散法制备白藜芦醇长循环热敏脂质体后,再用冷冻干燥法来制备白藜芦醇长循环热敏脂质体的前体。采用电势测定仪、HPLC等方法对该脂质体的包封率、粒径、稳定性、载药量、电位、释放度等来展开系统的检查。结果:白藜芦醇长循环热敏前体脂质体水合后形成白藜芦醇长循环热敏脂质体,粒径均值为(107.9±3.6)nm,Zeta电位的均值为(-12.2±1.6)m V,包封率可达89.4%;该脂质体在相变温度42℃下药物释放达到94%以上。结论:采用长循环热敏来制备的白藜芦醇前体脂质体含量与包封率检查方法准确、快速、简单且方法简便易行。载药量大,包封率好,工艺比较稳定。本实验可为新型白藜芦醇静脉注射用热敏脂质体的研究提供基础。     

热敏长循环脂质体的研究进展

简述长循环脂质体及热敏脂质体的制备原理及国内外研究进展, 将两种脂质体结合构成新型脂质体——热敏长循环脂质体, 并展望新型脂质体的研究前景.     

维甲酸脂质体在小鼠体内的药物动力学及组织分布

目的考察2种全反式维甲酸(ATRA)脂质体静脉给药后在小鼠体内的药物动力学和组织分布。方法分别采用不饱和豆磷脂(SPC),以及SPC与聚乙二醇-磷脂酰乙醇胺(PEG-PE)以一定比例混合的混合物为膜材,利用乙醇注入法制备全反式维甲酸普通脂质体和长循环脂质体,静脉注射后采用HPLC法测定小鼠血浆及各组织中的药物浓度。结果普通脂质体和长循环脂质体的AUC分别是以游离药物给药组的2.58倍和5.00倍,t1/2分别由2.66 h延长至3.74 h和6.39 h,脂质体在肝中分布显著增加。结论2种ATRA脂质体能够延缓药物释放,增强药物靶向性。     

依托泊苷长循环脂质体工艺处方设计与优化的研究

目的优化依托泊苷长循环脂质体的制备处方及工艺。方法以两亲性聚乙二醇一二硬脂酰磷脂乙醇胺为修饰体，采用薄膜超声．挤压法制备空白长循环脂质体；铵离子梯度法包封依托泊苷，制备依托泊苷长循环脂质体。以包封率为考察指标，采用正交设计法优化依托泊苷长循环脂质体的制备处方及工艺。结果优化后的依托泊苷长循环脂质体的工艺和处方：药脂比例为1：5tool·mol^-1、胆固醇与磷脂比例为0．3：1（W／w）、硫酸铵离子浓度为200mmol·L%^-1、包封温度为55℃。长循环脂质体平均粒径均小于1μm，药物平均包封率86．45％。结论该方法包封率高、粒径小且分布较窄，简便易行。     

Therapeutic efficacy of the combination of doxorubicin-loaded liposomes with inertial cavitation generated by confocal ultrasound in AT2 Dunning rat tumour model

Abstract

The combination of liposomal doxorubicin (DXR) and confocal ultrasound (US) was investigated for the enhancement of drug delivery in a rat tumour model. The liposomes, based on the unsaturated phospholipid dierucoylphosphocholine, were designed to be stable during blood circulation in order to maximize accumulation in tumour tissue and to release drug content upon US stimulation. A confocal US setup was developed for delivering inertial cavitation to tumours in a well-controlled and reproducible manner. In vitro studies confirm drug release from liposomes as a function of inertial cavitation dose, while in vivo pharmacokinetic studies show long blood circulation times and peak tumour accumulation at 24–48?h post intravenous administration. Animals injected 6?mg kg^?1 liposomal DXR exposed to US treatment 48?h after administration show significant tumour growth delay compared to control groups. A liposomal DXR dose of 3?mg kg^?1, however, did not induce any significant therapeutic response. This study demonstrates that inertial cavitation can be generated in such a fashion as to disrupt drug carrying liposomes which have accumulated in the tumour, and thereby increase therapeutic effect with a minimum direct effect on the tissue. Such an approach is an important step towards a therapeutic application of cavitation-induced drug delivery and reduced chemotherapy toxicity.     

8-氯腺苷长循环脂质体的制备及其在大鼠体内的药代动力学

Aim To prepare 8-chloro-adenosine (8-Cl-A) long circulation liposomes with high entrapped efficiency and prolonged action-time of 8-Cl-A in vivo. Methods To prepare 8-Cl-A long circulation liposomes of Manometer size by improved multiple emulsion. The entrapped efficiency, size and size distribution of 8-Cl-A long circulation liposomes were determined, and its pharmacokinetics in rats was evaluated. Results The entrapped efficiency of 8-Cl-A long circulation liposomes was 62.70% and mean diameter of the liposomes was 79.9 rim. The pharmacokinetics studies indicated that 8-Cl-A long circulation liposomes showed higher drug concentration and larger AUC values than that of 8-Cl-A after iv to rats. Conclusion 8-Cl-A long circulation liposomes could prolong the action-time of 8-Cl-A in vivo.     

IN VIVO TRAFFICKING OF LONG-CIRCULATING LIPOSOMES IN TUMOUR-BEARING MICE DETERMINED BY POSITRON EMISSION TOMOGRAPHY

Various kinds of long-circulating liposome, such as ganglioside GM1-, polyethyleneglycol- (PEG-), and glucuronide-modified liposomes, have been developed for passive targeting of liposomal drugs to tumours. To evaluate the in vivo behaviour of such long-circulating liposomes, we investigated the liposomal trafficking, especially early trafficking just after injection of liposomes, by a non-invasive method using positron emission tomography (PET). Liposomes composed of dipalmitoylphosphatidylcholine, cholesterol, and modifier, namely, GM1, distearoylphosphatidylethanolamine (DSPE)–PEG or palmityl-D -glucuronide (PGlcUA), were labelled with [2-¹⁸F]-2-fluoro-2-deoxy-D -glucose ([2-¹⁸F]FDG), and administered to mice bearing Meth A sarcoma after having been sized to 100 nm. A PET scan was started immediately after injection of liposomes and continued for 120 min. PET images and time–activity curves indicated that PEG liposomes and PGlcUA liposomes were efficiently accumulated in tumour tissues time dependently from immediately after injection. In contrast, GM1 liposomes accumulated less in the tumour as was also the case for control liposomes that contained dipalmitoylphosphatidylglycerol (DPPG) instead of a modifier. Long-circulating liposomes including GM1 liposomes, however, remained in the blood circulation and avoided liver trapping compared with control DPPG liposomes. These data suggest that PGlcUA and PEG liposomes start to accumulate in the tumour just after injection, whereas GM1 liposomes may accumulate in the tumour after a longer period of circulation.     

Liposomal topotecan formulation with a low polyethylene glycol grafting density: pharmacokinetics and antitumour activity

Objectives PEGylated liposomes could evade recognition by the reticulo‐endothelial system and prolong the circulation time of vesicles, resulting in enhanced targeting efficiency and antitumour effect. Typically, vesicles are modified with distearoylphosphatidylethanolamine (DSPE)‐polyethylene glycol (PEG) at a high PEG grafting density. However, long circulation time and slow drug release rate might induce severe hand‐foot syndrome in clinical practice. In this study, a liposomal topotecan formulation with a low PEG grafting density was prepared and its pharmacokinetics, acute toxicity and antitumour effect were investigated. Methods Topotecan was loaded into liposomes using an ammonium sulfate gradient. The resulting formulation was injected to healthy Wistar rats at different dose levels to investigate whether its clearance followed linear kinetics. Biodistribution was performed in Lewis lung cancer‐bearing mice. The acute toxicity was evaluated in healthy mice and beagle dogs. To compare the antitumour effects of different formulations and dose schedule, RM‐1 prostate, Lewis lung, H446 and L1210 cancer models were used. Key findings Topotecan could be encapsulated into low DSPE‐PEG liposomes with ～100% loading efficiency. The clearance of the liposomal formulation followed linear kinetics at a dose level ranging from 0.5 to 4 mg/kg despite the fact that the vesicles were coated at a low PEG density. Compared with free topotecan the liposomal formulation preferentially accumulated into tumour zones instead of normal tissues. Both formulations could rapidly accumulate into liver and tumour, but the liposomal formulation was cleared from tissues at a slow rate relative to the conventional formulation. In rats and beagle dogs, liposomal formulations could not induce skin toxicity. In all the tumour models, smaller split doses were more therapeutically active than larger doses when the overall dose intensity was equivalent. Conclusions This has been the first report that plasma kinetics of a liposomal formulation with a low PEG density followed linear kinetics. Moreover, due to its short circulation half‐life, the formulation did not induce skin toxicity. Our data revealed that the dose schedule of liposomal drugs should be adjusted in accordance with the biophysical and biological properties of the formulations to achieve the optimal therapeutic efficacy.     

新型热敏脂质体的研究进展

综述了近几年出现的新型热敏脂质体：长循环热敏脂质体，磁性热敏脂质体，免疫热敏脂质体和多聚物热敏脂质体     

Enhanced in vitro cellular uptake of P-gp substrate by poloxamer-modified liposomes (PMLs) in MDR cancer cells

Poloxamer-modified liposomes (PMLs) were prepared using poloxamers (P85 and F68) by the thin-film hydration method for overcoming the multidrug resistance and thereby enhancing the intracellular uptake of specific substrates of P-gp, rhodamine 123 (R123). The prepared liposomes, plain liposomes (PLs) and PMLs, were characterized by particle size, zeta potential and drug entrapment efficiency, and assessed by in vitro cellular uptake using KB and KBV20C (P-gp over-expression cell line) cells. The transmission electron microscopy study revealed the spherical shape of the prepared liposomes. No significant difference was observed between the PMLs and liposome without poloxamer (PLs) in the particle size (～160?nm) and zeta potential (～?5?mV). The in vitro cellular uptake study showed that P85-modified liposomes (PML-P85) significantly increased the internalization of R123 in MDR tumour cells. Our results showed that PML-P85 could be an effective carrier for anticancer drugs in MDR cancer therapy.     

Mannosylated liposomes improve therapeutic effects of paclitaxel in colon cancer models

Mannose receptor (MR) is a highly effective endocytic receptor. It is closely related to tumour immune escape and metastasis. We found that MR was highly expressed in some colon cancer cell lines such as CT26 and HCT116 cells. Therefore, MR might be a potential target in colon cancer therapy. In this study, we aimed to develop mannosylated liposomes containing anticancer drug paclitaxel and investigate the potential effects on targeted therapy for colon cancer. Mannosylated liposomes were prepared by film dispersion method. Characterisation, drug release behaviour, cytotoxicity, cellular uptake, anti-tumour efficacy and safety profiles of liposomes were investigated. The results showed that mannosylated liposomes had a higher CT26 cells uptake efficiency and tumour inhibition rate, which might be due to the target effect to MR. And no notable toxicity was observed. Taken together, these data demonstrated that mannosylated liposomes could target colon cancer and improve the efficacy of chemotherapy.     

THE EFFECT OF ADRIAMYCIN AGAINST A LIVER METASTATIC MODEL BY ENCAPSULATION IN LIPOSOMES

Antitumour activities of liposomes containing adriamycin (L-ADM) and their distribution process into tumour cells were analysed. The lipid composition of the liposomes was dimyristoylphosphatidylglycerol (DMPG)/egg phosphatidylcholine/cholesterol/adriamycin (ADM) in a molar ratio of 11·4 : 2 : 12 : 1·3. Liver-metastasizing murine tumour models, M5076 and L5178Y-ML, were used. In vivo antitumour effect against these tumour models was assessed from increase in life span (ILS). The survival prolongation effect of L-ADM in mice with liver failure caused by M5076 was significantly higher than that of F-ADM. In contrast, significant enhancement of the effects by encapsulation in liposomes was not observed in L5178Y-ML-bearing mice. In vitro cytostatic activities of L-ADM against M5076 cells as well as against other tumour cell lines were lower than those of F-ADM. The in vitro kinetic study of the distribution of L-ADM to the tumour cells revealed that ADM in L-ADM was taken up into the tumour cells mainly after it was released from the liposomes rather than taken up as the liposomal form. Among the cell lines tested, M5076 cells had the highest phagocytic activity and therefore the highest uptake activity of ADM during incubation with L-ADM. These findings suggest that the augmented antitumour activity of L-ADM in M5076-bearing mice was the result of phagocytosis of L-ADM by M5076 cells as well as the reduction of toxicity, prolonged retention of ADM in systemic circulation, and liver accumulation of ADM after administration of L-ADM.     

Preparation, characterization, and biodistribution study of technetium-99m-labeled leuprolide acetate-loaded liposomes in ehrlich ascites tumor-bearing mice

The purpose of this study was to prepare conventional and sterically stabilized liposomes containing leuprolide acetate in an attempt to prolong the biological half life of the drug, to reduce the uptake by reticuloendothelial system (RES), and to reduce the injection frequency of intravenously administered peptide drugs. The conventional and sterically stabilized liposomes containing leuprolide acetate were prepared by reverse phase evaporation method and characterized for entrapment efficiency and particle size. Radiolabeling of leuprolide acetate and its liposomes was performed by direct labeling with reduced technetium-99m. Its biodistribution and imaging characteristics were studied in ehrlich ascites tumor (EAT)-bearing mice after labeling with technetium-99m. The systemic pharmacokinetic studies were performed in rabbits. A high uptake by tumor was observed by sterically stabilized liposome containing leuprolide acetate compared with free drug and conventional liposomes. The liver/tumor uptake ratio of free drug, conventional (LL), and sterically stabilized liposomes (SLL5000 and SLL2000) was found to be 20, 7.99, 1.63, and 1.23, respectively, which showed the increased accumulation of sterically stabilized liposomes in tumor compared with the free drug and conventional liposomes at 24 hours postinjection. Liver uptake of sterically stabilized liposomes was still 7-fold less than the conventional liposomes. The marked accumulation of liposomes in the tumor-bearing mice was also documented by gamma scintigraphic studies. The findings demonstrate the distribution of these liposomes within solid tumor and prove that the sterically stabilized liposomes experience increased tumor uptake and prolonged circulation half life. Hence these findings will be relevant for the optimal design of long circulating liposomes for the peptide drugs and for targeting of liposomes toward tumor.