Double liposomes mediated dual drug targeting for treatment of Helicobacter pylori infections

In the present study the potential of phosphatidylethanolamine (PE) lipid anchored double liposomes (DL) to incorporate two drugs in a single system is exploited as a tool to augment the H. pylori eradication rate. Preparation of DL involves two steps, first formation of primary (inner) liposomes by thin film hydration method containing one drug, then addition of suspension of inner liposomes on thin film of lipid containing the other drug. The success of formation of DL was characterized by optical and transmission electron microscopy. Quantitation of DL-bacterial interaction was evaluated in terms of percent growth inhibition (%GI) on reference strain of H. pylori ATCC 26695. To confirm specific binding efficacy of DL to H. pylori PE surface receptor we performed an agglutination assay. Agglutination in DL treated H. pylori suspension suggested selectivity of DL towards the PE surface receptor of H. pylori. Monotherapy is generally not recommended for treatment of a H. pylori infection due to the danger of development of resistance and unacceptably low eradication rates. Therefore combination therapy with amoxicillin trihydrate (AMOX) as anti-H. pylori agent and ranitidine bismuth citrate (RBC) as antisecretory agent were selected for the study with an expectation that this dual-drug delivery approach will exert acceptable anti-H. pylori activity.     

Preparation of double liposomes and their efficiency as an oral vaccine carrier

The usefulness of double liposomes (DL), liposomes containing liposomes inside, as an oral vaccine carrier was examined. Ovalbumin (OVA) encapsulating liposomes sized to 230 nm (small liposomes, SL) were prepared by the glass-beads (GB) method and sequential sonication and extrusion. For the purpose of stabilizing the model antigen, DL containing SL were prepared by the GB method and the reverse-phase evaporation (REV) method. They were named GB-DL and REV-DL, respectively. The morphological structure of DL was confirmed using confocal laser scanning microscopy and scanning electron microscopy by the freeze-fracture method. DL showed suppressed release of OVA and stabilized OVA in pepsin solution as compared with SL. BALB/c mice were immunized with OVA solution, SL and DL suspension by oral administration. Significantly higher levels of IgA in feces were observed in mice immunized with SL and REV-DL as compared with OVA solution, and REV-DL tended to show the higher level of IgA than SL. REV-DL elicited significantly higher anti-OVA IgG responses as compared with OVA solution. Furthermore, GB-DL tended to raise the IgG level as compared with SL. The results suggest that DL have the potential to be an effective carrier for oral immunization.     

肺靶向阿奇霉素脂质体的制备及其在小鼠体内的分布

目的研究肺靶向阿奇霉素阳离子脂质体的制备方法并考察其在小鼠体内的分布。方法利用旋转薄膜-冻融法制备肺靶向阿奇霉素脂质体。用高效液相色谱法测定给药后小鼠体内各组织中的药物浓度。结果制得的脂质体平均粒径为6.582 μm，表面电荷为+19.5 mV，包封率大于75%，稳定性好。药物体外释药符合Higuchi方程。小鼠尾静脉给药后，阳离子脂质体主要被肺摄取，在肺部的滞留时间明显延长，AUC值约为阿奇霉素溶液的8.4倍。结论采用薄膜-冻融法，添加十八胺可制得具有较高包封率及稳定性的阿奇霉素阳离子脂质体，在小鼠肺部的分布优于注射液，能达到肺靶向目的。     

Preparation of novel double liposomes using the glass-filter method

The glass-filter method, a newly developed preparative method for liposomes, was applied for preparation of novel double liposomes. Double liposomes were prepared by filtering a suspension of liposomes prepared using a G4 filter (pore size: 10-16 microm) into a G3 filter (pore size: 40-100 microm) coated with a similar lipid layer. The morphological structure of the double liposomes was confirmed using scanning electron microscopy by the freeze-fracture method to be multivesicular vesicles consisting of small liposomes enveloped in larger liposomes. The diameter of liposomes prepared using the G4 filter was 0.8-2 microm and that of liposomes prepared using the G3 filter or double liposomes was 5-10 microm. These results suggested that the particle size of liposomes is dependent on the pore size of the glass-filter. The encapsulation efficiencies of double liposomes for brilliant blue FCF (BB) and erythrosine (ER) were higher than those of liposomes prepared by the standard Bangham method. Double liposomes showed suppressed release of BB or ER compared with normal liposomes. In particular, no release of BB was observed from the double liposomes prepared with stearylamine. These findings implied that the outer lipid layer protects the inner liposomes. The glass-filter method is the only method that we can get the double liposomes in a short period, and double liposomes prepared by this novel method had adequate size and good stability in vitro.     

Efficient drug delivery to atherosclerotic lesions and the antiatherosclerotic effect by dexamethasone incorporated into liposomes in atherogenic mice

In order to confirm the efficacy of dexamethasone (DXM) incorporated into liposomes (DXM-liposomes) on atherosclerosis, drug delivery to atherosclerotic lesions and the antiatherosclerotic effect by DXM-liposomes were investigated in atherogenic mice. DXM-liposomes were prepared with egg yolk phosphatidylcholine, cholesterol and dicetylphosphate in a lipid molar ratio of 7/2/1 by the hydration method and then adjusted to three different particle sizes to clarify the influence of particle size on the drug delivery to atherosclerotic lesions and the effect on atherosclerosis. The particle sizes of DXM-liposomes were 519 nm (L500), 202 nm (L200) and 68.6 nm (L70), respectively. In both size, DXM concentration and DXM/lipid molar ratio in DXM-liposomes suspension were 1 mg DXM/ml and 0.134 mol DXM/mol total lipids, respectively. Atherogenic mice used as an experimental model develop an atherosclerotic lesion in the aorta and they were prepared by feeding an atherogenic diet for 14 weeks. The aortic pharmacokinetics of DXM-liposomes was examined by intravenous administration to atherogenic mice. The aortic uptake clearance of DXM in atherogenic mice treated with L200 was 2.6–3.2 fold greater than that in animals treated with L500, L70 or free DXM (f-DXM). Furthermore, the effects of DXM-liposomes on atherosclerosis were examined by intravenous administration to atherogenic mice once a week from 8 to 14 weeks. The antiatherosclerotic effects of DXM-liposomes were evaluated by determination of the aortic cholesterol ester (CE) level. The aortic CE level in atherogenic mice treated with L200 (55 μg DXM/kg) was significantly lower than that in animals treated with PBS. The antiatherosclerotic effect of L200 (55 μg DXM/kg) was significantly more potent than that of f-DXM (550 μg DXM/kg). These findings suggest that efficient delivery of DXM to the atherosclerotic lesions by L200 induces an excellent antiatherosclerotic effect at a lower dose. Therefore, L200 may be useful in the development of drug delivery systems for atherosclerotic therapy.     

Evaluation of proinflammatory cytokine production and liver injury induced by plasmid DNA/cationic liposome complexes with various mixing ratios in mice

The purpose of this study was to investigate the cytokine production and liver injury induced by lipoplexes prepared with DOTMA/cholesterol and DOTAP/cholesterol liposomes with various mixing ratios in mice. Lipoplexes were prepared with pCMV-Luc and DOTMA/cholesterol or DOTAP/cholesterol liposomes. After intravenous administration into the mice, organ luciferase activity and serum TNFα and ALT were measured to evaluate the transfection efficacy, cytokine production and liver injury. After intravenous administration of these lipoplexes, basically the serum TNFα and ALT levels were in agreement with the transfection efficacy of the lipoplexes. The cytokine production and liver injury were markedly suppressed by reducing the pDNA dose, and achieved normal levels at a pDNA dose of 0.47 mg/kg. As far as the effects of the charge ratio at this low pDNA dose are concerned, the charge ratios of the lipoplexes affected the transfection efficacy, but not the cytokine production and liver injury. After intravenous administration of either DOTAP/cholesterol or DOTMA/cholesterol liposomes, serum TNFα and ALT levels were normal, suggesting that liver injury as well as cytokine production was caused by lipoplexes, but not by cationic liposomes. This information will be valuable for the future optimization of the preparation conditions of lipoplexes for use in clinical gene therapy.     

依托泊苷隐形前体脂质体的构建及家兔体内药动学研究

构建依托泊苷隐形前体脂质体，并考察其在家兔体内的药动学。采用薄膜分散法构建窄白隐形脂质体；硫酸铵梯度法包封依托泊苷；结合真空冷冻干燥技术构建依托泊苷隐形前体脂质体。采用凝胶色谱法测定脂质体包封率；透射电镜观察脂质体的形态；电泳光散射技术测定Zeta电位与粒径分布；以市售依托泊苷注射液和普通脂质体为参比制剂，评价其在家兔体内药动学特点。脂质体平均包封率为83．92％±3．65％，粒径为（124．5±26．9）nm，Zeta电位为（-39．50±1．04）mV，家兔单剂量静脉注射1．5mg／kg依托泊苷制剂后呈二室模型特征，依托泊苷隐形前体脂质体的T1/2β为（19．26±3．16）h，AUC为（26．04±3．53）μg／h／mL；注射液的T1/2β为（0．94±0．21）h，AUC为（0．98±0．26）μg／h／mL；普通脂质体的T1/2β为（7．99±1．36）h,AUC为（11．65±1．70）μg/mL。构建的隐形前体脂质体包封率高，且延长了依托泊苷在血液中的循环时间。     

Preparation,Optimization and Characterization of Bovine Lactoferrin‐loaded Liposomes and Solid Lipid Particles Modified by Hydrophilic Polymers Using Factorial Design

Bioadhesive liposomes and solid lipid particles (SLPs) modified by pectin and chitosan for oral administration of bovine lactoferrin (bLf) were prepared using a 2⁴ full‐factorial design to identify the key formulation variables influencing particle size and drug entrapment efficiency (EE). Netlike structures of the polymer–particle mixture consisting of a polymeric network in which multiple particles were imbedded were observed by scanning electron microscopy (SEM). Chemical stability of bLf after encapsulation into pectin‐ and chitosan‐modified liposomes and SLPs was confirmed by Fourier transform infrared spectra (FTIR). Bovine lactoferrin was located within phospholipid bilayer, whereas in SLPs bLf was within the matrix. The crystalline nature of bLf after encapsulation was investigated by differential scanning calorimetry (DSC) of drug‐loaded particles, indicating amorphous dispersion of bLf in the polymer–lipid matrix of pectin‐ and chitosan‐modified liposomes and SLPs. In vivo pharmacokinetic investigation of bLf in pectin‐ and chitosan‐modified liposomes and SLPs showed prolonged mean residence time (MRT) of bLf in rat blood and increased the relative bioavailability (F_bio%) by 1.95‐ to 2.69‐fold compared with free bLf. The developed carrier systems are considered to be promising vehicles for oral delivery.     

血栓靶向尿激酶脂质体的制备及其体内溶栓效果

目的制备血栓靶向的尿激酶脂质体,并在大鼠颈总动脉血栓模型上考察其溶栓情况。方法通过液相合成法合成出靶向于血栓的特异性配体H-Arg-Gly-Asp-Ser-OH (RGDS),并将其与monocarboxyl poly (ethylene glycol) 3 500 distearoyl phosphatidylethalnolamine (DSPE-PEG_{3 500}-COOH)偶联后插入到脂质体双层膜中得到血栓靶向尿激酶脂质体;通过制备方法的改进,以氢化豆磷脂在室温下制备尿激酶脂质体;在大鼠颈总动脉血栓模型上,考察了血栓靶向脂质体的体内溶栓效果。 结果所得的尿激酶脂质体包封率高、粒径小,稳定性好;与空白对照组的栓重相比,在相同剂量(60 kU·kg^-1,小剂量)下,游离尿激酶组几乎无任何改变,尿激酶脂质体组血栓重量稍有减轻但无显著性差异,血栓靶向尿激酶脂质体组血栓重量明显减轻(P<0.001);干重时的情况略有不同。与同剂量的普通脂质体相比,血栓靶向尿激酶脂质体溶栓效果显著改善(湿重时P<0.01,干重时P<0.05),表现出明显的靶向溶栓能力。 结论所制备的血栓靶向尿激酶脂质体具有靶向溶栓的效果。     

非特异靶向荷正电高分子磷脂脂质体的构建和体外评价

采用一种新设计的末端带有枝状结构寡赖氨酸聚乙二醇高分子磷脂为主要功能性辅料, 依照常规薄膜-水合和后续高分子插入两种方法制备了系列外表面带正电荷的高分子脂质体。激光衍射粒径仪研究证明, 常规脂质体制备方法和后续高分子插入都可以制备纳米、粒径均匀、外表面携带不同密度正电荷的高分子磷脂脂质体, 正电荷密度不同并不影响脂质体的粒径和分布。后续高分子插入过程不影响脂质体的载药工艺, 不干扰脂质体的载药量, 不引起脂质体的形态和粒径变化, 也不诱发脂质体内部包裹的药物早期泄漏。体外细胞学实验证明这种荷正电高分子脂质体局部电荷密度高, 对细胞有显著非特异性靶向作用。     

Anxiety and cognitive effects of quercetin liposomes in rats

Quercetin, an effective flavonol used as an antioxidant, was investigated for its anxiolytic and cognitive activities in male Wistar rats. Oral quercetin (300 mg/kg body weight/day) was compared with oral and intranasal quercetin liposomes (20 microg/day). Quercetin liposomes, in a mixture of egg phosphatidylcholine, cholesterol, and quercetin (2:1:1) and dispersed in 50% polyethylene glycol in water, were approximately 200 nm in mean particle diameter and negative surface charge with a range of encapsulation efficiency of 60% to 80%. Anxiolytic and cognitive-enhancing effects of quercetin, conventional and liposomal, were subjected to elevated plus maze and Morris water maze tests, respectively. Both conventional and quercetin liposomes showed anxiolytic and cognitive-enhancing effects. A lower dose and a faster rate were observed with intranasal quercetin liposomes when compared with oral quercetin, conventional and liposomal. The intranasal quercetin liposomes are effective in the delivery of quercetin to the central nervous system.     

2,3,7,8-Tetrachlorodibenzo-p-dioxin: Acute oral toxicity in hamsters

The acute oral toxicity of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) was evaluated in hamsters. Male golden Syrian hamsters received 0 (corn oil only), 300, 600, 1000, 3000, or 6000 μg TCDD/kg body wt by single-dose gavage. To facilitate dosage, TCDD was fed as a suspension in acetone/corn oil (1:9). The 55-day single-dose oral LD50 was 5051 μg/kg (3876–18,487 μg/kg, 95% confidence interval). Deaths occurred from Day 9 through Day 43 following single-dose administration. Initially, no hamsters exhibited adverse effects related to dosage with TCDD, but 4–5 weeks following dosage, hamsters of the 1000, 3000, and 6000 μg/kg dose groups began to develop unkempt hair coats. A dose-related depression of mean body weight when compared to control weights was apparent in hamsters of the 1000, 3000, and 6000 μg/kg dose groups by 3 weeks posttreatment. Gross necropsy revealed the primary target organs affected in the hamster to be the same as in other laboratory species, namely, liver and thymus; this was accompanied by a slight decrease in adipose tissue reserves. No other significant effects were noted upon necropsy. Based on these results, the hamster appears to be much less sensitive than other laboratory species to the acute oral toxicity of TCDD.     

雷公藤内酯醇固体脂质纳米粒的制备及理化性质

目的：以聚乙二醇单硬脂酸酯表面修饰材料结合到固体脂质纳米粒（solid lipid nanoparticles,SLN）,以雷公藤内酯醇（triptolide,TPL）为模型药,制备一种具有良好亲水亲脂性的雷公藤内酯醇固体脂质纳米粒。方法：采用熔融-乳化法制备固体脂质纳米粒。通过单因素考察、中心复合设计（central composite design,CCD）,考察脂质材料、聚山梨醇酯-80和PEG-stearate（PEG-SA）三个因素对TPL-SLN粒径、包封率和载药量的影响。通过透射电镜、热分析和X-射线衍射考察TPL-SLN的理化性质,并考察其固体脂质纳米粒的稳定性以及体外释放情况。用MTT法测定其对人正常肝L02细胞和肝癌细胞HepG2的增殖抑制作用并计算其IC₅₀。结果：最优的处方：脂质材料为7.5%,聚山梨醇酯80（Tween 80）为2%和PEG-SA为2%,其粒径（193.43±6.07）nm,包封率（87.63±0.09）%,载药量（0.33±0.01）%。透射电镜观察所制备的纳米粒的形态近似于球形,DSC分析和X-射线衍射证实TPL以非晶型的形式存在于固体脂质纳米粒中。稳定性考察发现纳米粒粒径在一个月的贮存期基本没有变化（P>0.05）,体外释放表明TPL-SLN具有体外缓释特性。TPL-SLN对肿瘤细胞的抑制作用强于正常肝细胞。结论：雷公藤内酯醇聚乙二醇修饰固体脂质纳米粒有望开发为临床口服用药新剂型。     

Chitosan-coated liposomes: characterization and interaction with leuprolide

The objective of the present work was to investigate the effect of chitosan concentration and lipid type on the characteristics of chitosan-coated liposomes and their interactions with leuprolide. Liposomes from lipid of high purity and low purity were prepared and coated by chitosan. Physical properties, drug entrapment efficiency, and stability upon dilution were respectively compared. Results showed that the particle size increment of liposomes from low purity lipid was larger than that from high purity lipid, indicating a thicker coating layer. The high zeta potential of particles from low purity lipid was thought to play an important role in the resistance to flocculation. As to particles from high purity lipid, polymer bridging caused flocculation at low polymer concentration while at high concentration, the adsorbed chitosan molecule led to steric stabilization. Drug entrapment efficiency decreased as chitosan was added to liposomes, showing the disturbance of bilayers. Upon dilution, the leakage of leuprolide from low purity liposomes was larger than that from high purity liposomes. In conclusion, low purity lipid possessed more negative charge and formed thicker adsorptive layer by stronger electrostatic attraction with chitosan. The interaction between chitosan and the polar head groups on the surface of phospholipid bilayers may interfere with leuprolide entrapped in liposomes and result in the leakage of leuprolide.     

银杏内酯B脂质体的处方与制备工艺研究

目的 将银杏内酯B（ginkgolide B,GB）制备成脂质体,增加GB在水中的分散性和稳定性。方法 采用超滤离心法分离脂质体与游离药物,HPLC测定脂质体中GB的含量与包封率,采用薄膜分散法制备GB脂质体;通过单因素与正交试验分析药脂比、胆固醇用量、装载量、水化温度和水化时间等因素对包封率的影响,以外观、包封率、粒径为评价指标确定GB脂质体的最佳处方和制备工艺。结果 GB脂质体的最佳处方为10 mg GB、160 mg蛋黄卵磷脂、40 mg胆固醇、8 mg维生素E、58 mg DSPE-PEG2000、5 mL PBS缓冲液;优化后的工艺条件为GB与脂质辅料溶于无水乙醇中,33℃水浴条件下减压旋转蒸发除乙醇,pH 6.5 PBS缓冲液水化脂质薄膜,水化温度35℃,时间120 min,粗脂质体混悬液冰水浴超声6 min,超声功率120 W。制备的GB脂质体混悬液微泛蓝色乳光、可透光,粒径为（126±4） nm,包封率>87%,放置24 h无聚集、无沉降。结论 采用薄膜法在实验室阶段成功制备了稳定的GB脂质体,确定了最优制备处方和制备工艺,为GB制剂的剂型研究做出探索和提供参考。     

Skin penetration and deposition of carboxyfluorescein and temoporfin from different lipid vesicular systems: In vitro study with finite and infinite dosage application

The aim of the present research is to evaluate the influence of different lipid vesicular systems as well as the effect of application mode on skin penetration and deposition behaviors of carboxyfluorescein (hydrophilic model drug) and temoporfin (lipophilic model drug). All of the lipid vesicular systems, including conventional liposomes, invasomes and ethosomes, were prepared by film hydration method and characterized for particle size distribution, ζ-potential, vesicular shape and surface morphology, in vitro human skin penetration and skin deposition. Dynamic light scattering (DLS) and transmission electron microscopy (TEM) defined that all of lipid vesicles had almost spherical structures with low polydispersity (PDI < 0.2) and nanometric size range (z-average no more than 150 nm). In addition, all lipid vesicular systems exhibited a negative zeta potential. In vitro skin penetration and deposition experiments demonstrated that, in the case of CF with finite dose application (10 μl/cm2) and infinite dose application (160 μl/cm2), lipid vesicular systems, especially ethosomes and invasomes, compared with non-vesicular systems, can significantly improve the delivery of hydrophilic drug such as carboxyfluorescein into skin deep layers or across the skin. While in the case of mTHPC with finite and infinite dose application, most of drug accumulation was observed in the skin superficial layer for both lipid vesicular systems and non-vesicular systems. The results also revealed that the factors influencing the drug skin distribution concern the physicochemical characteristics of the drug, the choice of the vehicle formulation and the application mode applied.     

Subacute toxicity of all‐trans‐retinoic acid loaded biodegradable microspheres in rats

Biodegradable microspheres containing all‐trans‐retinoic acid (atRA) were prepared previously to enhance the clinical efficacy of atRA for chemoprevention. In this study, subacute toxicity of atRA in sustained release was evaluated after subcutaneous administration of 0, 25, 50, and 100 mg atRA/kg of atRA‐loaded microspheres. After the subcutaneous injection of atRA‐loaded microspheres, the atRA concentration in plasma was maintained in the range of 3.5–25 ng/ml for 2–3 weeks. When 100 mg atRA/kg was administered, the atRA concentration in plasma was maintained at levels greater than 10 ng/ml and severe toxic effects were observed. When the dose of 50 mg atRA/kg was administered, the plasma concentration of atRA was maintained below 10 ng/ml over 3 weeks and only mild signs of toxicity were observed. Therefore, it was concluded that the dosage of atRA‐loaded microspheres should be less than 50 mg atRA/kg for chemopreventive applications against carcinogenesis. Considering recovery from intoxication, the optimum interval for repeated injection of the microspheres was suggested to be over 4 weeks. In addition, it was found that the atRA concentration in plasma should be controlled below 10 ng/ml to minimize toxic effects of atRA. Drug Dev. Res. 59:326–332, 2003. © 2003 Wiley‐Liss, Inc.     

Efficient drug delivery to atherosclerotic lesions and the antiatherosclerotic effect by dexamethasone incorporated into liposomes in atherogenic mice

In order to confirm the efficacy of dexamethasone (DXM) incorporated into liposomes (DXM-liposomes) on atherosclerosis, drug delivery to atherosclerotic lesions and the antiatherosclerotic effect by DXM-liposomes were investigated in atherogenic mice. DXM-liposomes were prepared with egg yolk phosphatidylcholine, cholesterol and dicetylphosphate in a lipid molar ratio of 7/2/1 by the hydration method and then adjusted to three different particle sizes to clarify the influence of particle size on the drug delivery to atherosclerotic lesions and the effect on atherosclerosis. The particle sizes of DXM-liposomes were 519 nm (L500), 202 nm (L200) and 68.6 nm (L70), respectively. In both size, DXM concentration and DXM/lipid molar ratio in DXM-liposomes suspension were 1 mg DXM/ml and 0.134 mol DXM/mol total lipids, respectively. Atherogenic mice used as an experimental model develop an atherosclerotic lesion in the aorta and they were prepared by feeding an atherogenic diet for 14 weeks. The aortic pharmacokinetics of DXM-liposomes was examined by intravenous administration to atherogenic mice. The aortic uptake clearance of DXM in atherogenic mice treated with L200 was 2.6--3.2 fold greater than that in animals treated with L500, L70 or free DXM (f-DXM). Furthermore, the effects of DXM-liposomes on atherosclerosis were examined by intravenous administration to atherogenic mice once a week from 8 to 14 weeks. The antiatherosclerotic effects of DXM-liposomes were evaluated by determination of the aortic cholesterol ester (CE) level. The aortic CE level in atherogenic mice treated with L200 (55 microg DXM/kg) was significantly lower than that in animals treated with PBS. The antiatherosclerotic effect of L200 (55 microg DXM/kg) was significantly more potent than that of f-DXM (550 microg DXM/kg). These findings suggest that efficient delivery of DXM to the atherosclerotic lesions by L200 induces an excellent antiatherosclerotic effect at a lower dose. Therefore, L200 may be useful in the development of drug delivery systems for atherosclerotic therapy.     

Effect of Liposome Characteristics and Dose on the Pharmacokinetics of Liposomes Coated with Poly(amino acid)s

Long-circulating liposomes, such as PEG-liposomes, are frequently studied for drug delivery and diagnostic purposes. In our group, poly(amino acid) (PAA)-based coatings for long-circulating liposomes have been developed. These coatings provide liposomes with similar circulation times as compared to PEG-liposomes, but have the advantage of being enzymatically degradable. For PEG-liposomes it has been reported that circulation times are relatively independent of their physicochemical characteristics. In this study, the influence of factors such as PAA grafting density, cholesterol inclusion, surface charge, particle size, and lipid dose on the circulation kinetics of PAA-liposomes was evaluated after intravenous administration in rats. Prolonged circulation kinetics of PAA-liposomes can be maintained upon variation of liposome characteristics and the lipid dose given. However, the use of relatively high amounts of strongly charge-inducing lipids and a too large mean size is to be avoided. In conclusion, PAA-liposomes represent a versatile drug carrier system for a wide variety of applications.     

N-三甲基壳聚糖包覆牛血清白蛋白脂质体的制备及质量影响因素研究

目的:制备N-三甲基壳聚糖(TMC)包覆的牛血清白蛋白(BSA)脂质体,并考察其质量影响因素。方法:采用逆相蒸发法制备BSA脂质体,壳聚糖与碘甲烷进行季胺化反应合成TMC,用于脂质体包衣,制备TMC包覆的BSA脂质体。采用高速离心考马斯亮蓝G-250法测定包封率,考察脂类大豆卵磷脂(PC):胆固醇(CH):磷脂酰丝氨酸(PS)组成比、TMC与脂相质量比、离子强度对脂质体包封率和粒径的影响。结果:所考察因素对粒径和包封率均有影响,以脂类组成PC:CH:PS(8:9:1)、TMC与脂相质量比0.25:1、离子强度小于20 mmol·L~(-1)为宜,所制脂质体包封率为(46.82±2.07)%。结论:TMC可包覆BSA制备脂质体,所得制剂粒径均匀,稳定性好。