反义寡核苷酸脂质体复合物性质对细胞摄入行为的影响

目的研究影响反义寡核苷酸脂质体复合物的性质和细胞摄取的因素。方法逆相蒸发法制备3种不同的空白脂质体,与反义寡核苷酸混合得到复合物,显微镜观察其形态,琼脂糖电泳分析载药量,流式细胞仪测定阳性细胞百分率和平均荧光强度。结果高电荷密度的脂质体和低离子强度介质可使复合物发生凝聚,载药量和细胞摄入量依赖于空白脂质体和药物的比例以及脂质体膜表面的电荷密度。结论阳离子脂质体可以提高载药量和细胞的摄入,其程度与复合物比例、脂质体膜表面电荷密度等有关。     

反义寡核苷酸阳离子脂质体的制备和体外细胞摄取研究反义寡核苷酸阳离子脂质体的制备和体外细胞摄取研究

目的制备高效促进细胞摄取反义寡核苷酸(ASON)和保护ASON的脂质体。方法以3β［n-(n′,n′-二甲氨基乙基)氨甲酰基-胆固醇(DC-Chol)为类脂成分制备阳离子脂质体(以下简称DC-Chol脂质体),与ASON混合得到载药脂质体,测定载药率。用琼脂糖凝胶电泳分析载药脂质体的结构特点;流式细胞仪检测不同条件下细胞摄取荧光标记ASON的情况;变性聚丙烯酰胺电泳考察DC-Chol脂质体对ASON的保护作用。结果载药率与DC-Chol脂质体和药物的+/-电荷比有关,当+/-电荷比大于2时,载药率达90%以上;琼脂糖凝胶电泳显示ASON同时存在于DC-Chol脂质体的周围和包裹于其内部的两种形式;流式细胞仪测定结果表明,DC-Chol脂质体可明显增加细胞对ASON的摄取,阳性细胞染色率和胞内平均荧光强度均较对照组有明显增加,增加程度主要取决于+/-电荷比例,血清可降低细胞的摄取;变性聚丙烯酰胺电泳证实DC-Chol脂质体具有保护ASON的作用。结论DC-Chol脂质体具有显著增加细胞摄取ASON和保护ASON的作用,有望成为反义类药物的高效传递系统。     

脂质体介导C-erbB-2反义寡核苷酸转染小鼠乳腺癌TM40D细胞的效率及毒性

目的 探讨阳离子脂质体为载体的反义寡核苷酸（ODNs）转染小鼠乳腺癌TM40D细胞的最佳转染效率及对细胞的毒性作用。方法 分别将有／无脂质体介导的反义ODNs转染小鼠乳腺癌TM40D细胞,应用流式细胞仪观察不同时间的反义ODNs的转染效率,荧光显微镜观察反义ODNs在细胞内的分布,全自动生化分析仪检测转染培养上清液的乳酸脱氢酶（LDH）浓度。结果 无脂质体介导的反义ODNs转染细胞效率随着时间的延长增加,6h达到63．00％。脂质体介导的反义ODNs转染细胞4h时转染效率达到高峰为72．23％。细胞内荧光强度与细胞转染效率相关。无脂质体介导的FAM标记的反义ODNs分布在细胞浆,脂质体介导的反义ODNs在细胞浆及细胞核内均有分布。各组LDH浓度无统计学差异。结论 脂质体介导组反义ODNs转染效率高于无脂质体组,同时转染高峰提前出现。脂质体促进反义ODNs进入细胞核内。短时间内阳离子脂质体及反义ODNS对细胞的毒性不明显。     

谷甾醇葡萄糖苷和卞泽双重修饰肝实质细胞靶向阳性脂质体介导的基因转染和抗乙肝病毒作用

目的研究载乙型肝炎病毒(HBV)反义寡核苷酸的双重表面修饰肝实质细胞靶向阳性脂质体的基因转染，抗乙肝病毒作用和其介导基因转染的机制。方法以3β-［N-(N′,N′-二甲氨基乙基)-氨甲酰基］胆固醇(DC-Chol)和二棕榈酰磷脂酰胆碱(DPPC)为脂材，分别以谷甾醇葡萄糖苷(sito-G)和卞泽(Brij 35)为膜表面修饰成分，制备载HBV反义寡核苷酸的阳性脂质体。采用大鼠原代肝实质细胞和人肝癌细胞HepG 2.2.15，通过流式细胞分析、荧光显微镜观察和酶联免疫吸附试验(ELISA)，考察脂质体对基因转染的促进作用及其病毒抑制作用；通过评价渥曼青霉素、尼日利亚菌素以及无涎胎球蛋白对其病毒抑制作用的影响，探讨其转染机制。结果以sito-G和Brij 35对脂质体进行双重表面修饰，显著提高了脂质体的转染率和病毒抑制作用；荧光显微镜下观察到较强转染，反义寡核苷酸的胞内分布以在细胞核中为主；渥曼青霉素、尼日利亚菌素和无涎胎球蛋白均不同程度地降低了载反义寡核苷酸脂质体的病毒抑制作用。结论Brij 35和sito-G双重修饰阳性脂质体显示出较高的基因转染效率和显著的病毒抑制作用，其基因转染过程以内吞和膜融合为主，并表现出肝实质细胞表面去唾液酸糖蛋白受体 (ASGPR)的靶向选择性。     

多胺胆固醇缀合物纳米粒作为反义核苷酸传递系统的研究

目的研究多胺胆固醇缀合物传递反义核苷酸的能力。方法通过对自制脂质体的载药量、红细胞毒性、M3骨髓瘤细胞的转染实验。结果自制脂质体具有比常规脂质体良好的载药量,并且对红细胞毒性相对偏小,对M3骨髓瘤细胞具有一定的转染能力。结论自制的脂质体具有一定的应用前景。     

载基因纳米阳离子脂质体前体制剂的制备及性质研究

目的:制备稳定的载反义寡核苷酸的阳离子脂质体前体制剂。方法:以磷脂-二油酰磷脂酰乙醇胺(dioleoylphophatidylethanolamine,DOPE)-十八胺-胆固醇为类脂成分,采用薄膜超声-挤压制备空白阳离子脂质体,吸附-冷冻干燥法制备载反义寡核苷酸阳离子脂质体前体。激光粒度仪测定冷冻干燥前后脂质体Zeta电位及粒径,透射电镜观察其形态,葡聚糖凝胶柱分离未包封的反义寡核苷酸,紫外法测定冻干前后的载药率。结果:海藻糖与甘露醇及甘氨酸为较好的冻干保护剂,制得的阳离子脂质体前体带正电荷,规则球形,大小较均匀,海藻糖作为保护剂复溶前后平均粒径为175和320 nm左右,复融前后Zeta电位值在+32和+40 mV左右,脂质体的载药率复溶前后分别为87.6%与83.21%。结论:海藻糖作为冻干保护剂,薄膜超声挤压法与冷冻干燥法结合,可成功制备反义寡核苷酸阳离子脂质体前体制剂,稳定性大大改善。     

寡核苷酸聚赖氨酸修饰物的脂质体制备及其对HepG2细胞的细胞毒活性研究

目的研究反义寡核苷酸的聚赖氨酸修饰物对脂质体包封率的影响及对HepG2细胞活性的初步测定。方法利用反义药物的聚赖氨酸修饰物,采用薄膜分散法制备反义寡核苷酸及其聚赖氨酸修饰物的脂质体;紫外分光光度法测定包封率的差异并考察对HepG2细胞细胞毒活性的影响。结果高密度正电荷的聚赖氨酸与带负电荷的反义寡核苷酸偶联后,脂质体的载药量大大增加,并且细胞的摄入量增加,对HepG2细胞生长具有抑制作用。结论聚赖氨酸修饰物增加了反义寡核苷酸的脂质体包封率,有效诱导人肝癌细胞的凋亡作用。     

阳离子脂质体介导反义寡核苷酸肿瘤治疗的初步探索

目的：探讨阳离子脂质体（CL）介导反义寡核苷酸（ASODN）肿瘤治疗的效果。方法：以CL／ASODN复合物处理7721肝癌细胞，观察肝癌细胞的生长增殖和凋亡情况以及在体荷瘤小鼠治疗情况的考察。结果：CL／ASODN对7721肝癌细胞的抑制作用具有剂量和时间依赖性；荷瘤小鼠的实体瘤体积明显减小。结论：阳离子脂质体（CL）有望成为肿瘤治疗的理想载体。     

脂质体Geneshuttle20对STAT6反义核酸转染小鼠脾淋巴细胞影响的研究

目的探讨阳离子脂质体Geneshuttle20对STAT6反义核酸在小鼠脾淋巴细胞摄入、分布的影响作用。方法采用阳离子脂质体介导STAT6反义核酸转染小鼠脾淋巴细胞,应用流式细胞仪、荧光显微镜分别观察反义核酸的细胞摄入和胞内分布。结果反义核苷酸与脂质体(W/W)为2∶4时,细胞摄入率可以达到67.7%,较单独加入反义核酸提高转染效率6倍,细胞内平均荧光强度最强,细胞核染色较深。结论Geneshuttle20提高了细胞对反义寡核苷酸的摄取,促使其进入细胞核内发挥作用。     

血管内皮生长因子反义寡核苷核对前列腺癌细胞PC3生长特性的影响

目的探讨血管内皮生长因子(VEGF)反义寡核苷核对前列腺癌细胞PC3生长特性的影响。方法采用新型脂质体Oligofectamine携带VEGF反义寡核苷酸转染激素非依赖性前列腺癌细胞PC3,实验分为对照组、反义寡核苷核苷酸组和正义寡核苷酸组。Western Blot杂交的方法检测细胞VEGF蛋白的表达,四甲基偶氮唑蓝法(MTT)检测细胞增殖变化,流式细胞仪检测细胞凋亡情况。结果新型脂质体可以携带VEGF反义寡核苷酸转染前列腺癌细胞PC3,与对照组和正义寡核苷酸组比较,反义寡核苷酸组细胞VEGF蛋白的表达明显下降,增殖受到明显抑制,凋亡率增加。结论新型脂质体Oligofectamine可以携带VEGF反义寡核苷酸成功转染前列腺癌细胞PC3,抑制VEGF的表达,进而抑制肿瘤细胞的增殖,促进其凋亡。     

Synthesis, characterization and transfection activity of new saturated and unsaturated cationic lipids

We synthesized new cationic lipids, analogue to N-[1-(2,3-dioleoyloxy)propyl]-N,N,N-trimethylammonium chloride (DOTMA) and 1,2-dimyristyloxypropyl-3-dimethyl-hydroxyethylammonium bromide (DMRIE), in order to compare those containing a dodecyl chain with those having a relatively long chain with two or five double bonds, such as squalenyl and dihydrofarnesyl derivatives, or complex saturated structures, such as squalane derivatives. The fusogenic helper lipid dioleoylphosphatidylethanolamine (DOPE) was added to cationic lipids to form a stable complex. Liposomes composed of 50:50 w/w cationic lipid/DOPE were prepared and incubated with plasmidic DNA at various charge ratios and the diameter and zeta potential of the complexes were measured. The surface charge of the DNA/lipid complexes can be controlled by adjusting the cationic lipid/DNA ratio. Finally, we tested the in vitro transfection efficiency of the cationic lipid/DNA complexes using different cell lines. The transfection efficiency was highest for the dodecyloxy derivative containing a single hydroxyethyl group in the head, followed by the dodecyloxy and the farnesyloxy trimethylammonium derivatives. Instead the C27 squalenyl and C27 squalanyl derivatives resulted inactive.     

Enhancement of transfection activity of lipoplexes by complexation with transferrin-bearing fusogenic polymer-modified liposomes

We previously developed complexes of lipoplexes containing 3beta-(N-(N',N'-dimethylaminoethane)carbamoyl)cholesterol (DC-chol) and succinylated poly(glycidol)-modified liposome, which becomes fusogenic under weakly acidic condition, for use as a novel gene delivery system. This study explored the effect of lipoplex structures--the type of cationic lipid and cationic lipid/DNA charge ratio--on the transfection activity of those complexes. Three types of cationic lipid with different polar groups were used for the preparation of lipoplexes: DC-chol, N-[1-(2,3-dioleoyloxy)propyl]-N,N,N-trimethylammonium methylsulfate (DOTAP), and 3,5-dipentadecyloxybenzamidine (TRX-20) with dimethylamino group, trimethylammonium group, and benzamidine group, respectively. Complexation with the SucPG-modified transferrin-bearing liposomes affected transfection activity of these lipoplexes differently. The TRX-20 lipoplexes exhibited the most marked enhancement of transfection activity upon complexation with the SucPG-modified liposomes among these lipoplexes. The cationic lipid/DNA charge ratio of the lipoplex and the amount of the transferrin-bearing SucPG-modified liposomes associated to the lipoplex also affected the transfection activity of the resultant complexes. Highly potent gene vectors were obtained by adjusting these factors.     

Novel series of non-glycerol-based cationic transfection lipids for use in liposomal gene delivery.

A novel series of nontoxic and non-glycerol-based simple monocationic transfection lipids containing one or two hydroxyethyl groups directly linked to the positively charged nitrogen atom were synthesized. The in vitro transfection efficiencies of these new liposomal gene delivery reagents were better than that of lipofectamine, a widely used transfection agent in cationic lipid-mediated gene transfer. The most efficient transfection formulation was observed to be a 1:1:0.3 mol ratio of DHDEAB (N, N-di-n-hexadecyl-N,N-dihydroxyethylammonium bromide):cholesterol:HDEAB (N-n-hexadecyl-N,N-dihydroxyethylammonium bromide) using a DHDEAB-to-DNA charge ratio (+/-) of 0.3:1. Observation of good transfection at charge ratios lower than 1 suggests that the amphiphile-DNA complex may have net negative charge. Our results reemphasize the important point that in cationic lipid-mediated gene delivery, the overall charge of the lipid-DNA complex need not always be positive. In addition, our transfection results also imply that favorable hydrogen-bonding interactions between the lipid headgroups and the cell surface of biological membranes may have some role for improving the transfection efficiency in cationic lipid-mediated gene delivery.     

Optimization of cationic lipid/DNA complexes for systemic gene transfer to tumor lesions

Intravenous (i.v.) administration of cationic lipid N-[( 1-(2-3-dioleyloxy)propyl)]-N-N-N-trimethylammonium chloride (DOTMA)-based transfection complexes in mice with subcutaneous squamous cell tumors yielded plasmid delivery and expression in tumor lesions. The efficiency of gene transfer in tumors was significantly lower than in the lung. This was consistent with low plasmid levels associated with the tumor, suggesting that plasmid delivery to the tumor site was a limiting factor. Lowering the lipid/DNA charge ratio from 5:1 to 0.8:1 (+/-) did not change DNA levels in tumor but significantly reduced DNA levels in lung. However, expression levels were significantly reduced in both tissues at lower lipid/DNA charge ratios. Complexes prepared from small unilamellar liposomes gave significantly lower expression levels in the lungs but similar expression levels in tumors when compared to complexes prepared from larger unilamellar liposomes. The small liposome complexes were better tolerated than large liposome complexes. Varying the cationic lipid to colipid (cholesterol or DOPE) molar ratio from 4: 1 to 1: 1 significantly reduced expression levels in both tumor and lung. Cationic lipid substitution, using a cholesterol cationic lipid, diethyldiamino-carbamyl-cholesterol instead of DOTMA, produced reduced expression in all other tissues except tumor. Incorporation of PEG into preformed transfection complexes reduced DNA delivery to lung, increased circulation half-life, and enhanced DNA delivery to tumor. In a lung metastatic mouse tumor model, where the accessibility of the i.v. administered transfection complexes to tumor lesions should be less challenging, DOTMA: CHOL complexes (4: 1 lipid to colipid molar ratio, 3: 1 +/- lipid to plasmid charge ratio) were preferentially localized in tumor lesions. These data demonstrate that systemic gene transfer to distal tumor sites by lipid/ DNA complexes may be limited by low plasmid delivery. Modifying the chemical surface properties of transfection complexes enhanced both DNA delivery and expression in tumor and is one approach that may overcome limitations.     

Encapsulation of plasmid DNA in stabilized plasmid-lipid particles composed of different cationic lipid concentration for optimal transfection activity

In previous work (Wheeler et al. (1999) Gene Therapy 6, 271-281) we have shown that plasmid DNA can be entrapped in "stabilized plasmid lipid particles" (SPLP) using low levels (5-10 mol%) of cationic lipid, the fusogenic lipid dioleoylphosphatidylethanolamine (DOPE), and a polyethyleneglycol (PEG) coating for stabilization. The PEG moieties are attached to a ceramide anchor containing an arachidoyl acyl group (PEG-CerC20). However, these SPLP exhibit low transfection potencies in vitro as compared to plasmid/cationic lipid complexes formed with liposomes composed of cationic and neutral lipid at a 1:1 lipid ratio. The objective of this study was to construct SPLPs with increased cationic lipid contents that result in maximum transfection levels. A phosphate buffer detergent dialysis technique is described resulting in formation of SPLP containing 7-42.5 mol% DODAC with reproducible encapsulation efficiency of up to 80%. An octanoyl acyl group was used as anchor for the PEG moiety (PEG-CerC8) permitting a quick exchange out of the SPLP to further optimize the in vitro and in vivo transfection. We have demonstrated that this technique can be used to encapsulate either linearized DNA or supercoiled plasmids ranging from 3-20 kb. The SPLP formed could be isolated from empty vesicles by sucrose density gradient centrifugation, and exhibited a narrow size distribution of approximately 75 +/- 6 nm as determined by cryo-electron microscopy. The high plasmid-to-lipid ratio observed corresponded to one plasmid per particle. The SPLP consist of a lipid bilayer surrounding the plasmid DNA as visualized by cryo-electron microscopy. SPLP containing a range of DODAC concentrations were tested for in vitro and in vivo transfection. In vitro, in COS-7 cells transfection reached a maximum after 48 h. The transfection efficiency increased when the DODAC concentration in the SPLP was decreased from 42.5 to 24 mol% DODAC. Decreasing the cationic lipid concentration improved transfection in part due to decreased toxicity. In vivo studies using an intraperitoneal B16 tumor model and intraperitoneal administration of SPLP showed maximum transfection activity for SPLP containing 24 mol% DODAC. Gene expression observed in tumor cells was increased by approximately one magnitude as compared to cationic lipid/DNA complexes. The SPLP were stable and upon storage at 4 degrees C no significant change in the transfection activity was observed over a one-year period. Thus this phosphate buffer detergent dialysis technique can be used to generate SPLP formulations containing a wide range of cationic lipid concentrations to determine optimal SPLP composition for high transfection activity and low toxicity.     

A lipid-based delivery system for antisense oligonucleotides derived from a hydrophobic complex

Antisense oligodeoxynucleotides (ASOs) prevent expression of proteins by binding to specific regions of mRNA. This report investigates a potential lipid-based delivery system for ASO. A hydrophobic complex was recovered following addition of cationic lipids to ASOs in a Bligh and Dyer monophase [chloroform/methanol/water (1:2.1:1, v/v/v)]. The addition of monovalent cationic lipids (dioleyldimethylammonium chloride, dimethyldioctadecylammonium bromide, dioleoyltrimethylammonium propane), resulted in > 95% recovery of the ASOs from the organic phase when ASO phosphate charge was neutralized. Cholesteryldimethylaminoethylcarbamate mediated efficient extraction at a charge ratio (+/-) > 5.2. ASOs could not be extracted into the organic phase by the polyvalent lipids, dioctadecylamidoglycyl spermine and 2,3-dioleyloxy-N-[2(sperminecarboxamido)ethyl]-N,N-dimethyl-1-propaminium trifluoroacetate, even at a charge ratio (+/-) > 5. Dioleoylphosphatidylethanolamine, but not dioleoylphosphatidylcholine, prevented formation and destabilized the hydrophobic complexes. The characterization of the hydrophobic complex led to the development of lipid-ASO particles containing dioleyldimethylammonium chloride, dioleoylphosphatidylethanolamine and poly(ethylene glycol)-conjugated phosphatidylethanolamine (LAPs). When FITC-labeled ASOs in LAPs were added to B-cell lymphoma cells (DoHH2) in vitro, cell-associated ASO decreased as poly(ethylene glycol)-conjugated phosphatidylethanolamine incorporation increased. Western Blot analysis demonstrated that no significant downregulation of Bcl-2 protein was observed when using LAPs. The results suggest that the use of stabilized PEG-conjugated lipids may be detrimental for cationic lipid-based ASO delivery.     

Intracellular Compartmentalization of DNA Fragments in Cultured Airway Epithelial Cells Mediated by Cationic Lipids

Purpose. The amount and intracellular distribution of DNA fragments (491 -bp) was characterized after transfection in vitro with a commercially available cationic lipid. Localization of fragment to the nucleus, its subcellular distribution, and integrity within the cells was determined for various times after transfection. Methods. Cystic fibrosis (CF) airway epithelial cells were transfected with ³²P and FITC labeled single-stranded (ss) or double-stranded (ds) DNA fragments complexed with Lipofectamine^® at various charge ratios. Results. A 5/1 (+/–) charge ratio was found to be the optimal ratio for transfection of both ss-and dsDNA. After a 5 h exposure, 7.51 ± 0.89% of the radioactivity was associated with the nuclear fraction whereas only 1.07 ± 0.23%, was found in the nuclear fraction when dsDNA was used. The nuclear radioactivity detected after a 24 h exposure was only 1/3 of that after 5 h. Analysis of fragment stability in the cytosolic and nuclear fractions showed the presence of intact fragment in each subcellular compartment. No intranuclear/intracellular fragment could be detected in control experiments with naked DNA. Conclusions. The results from these experiments indicate that small fragments of DNA can be efficiently and rapidly transferred intact to the cell nucleus using cationic lipids and that ssDNA fragments are more effective than dsDNA fragments for nuclear delivery.     

Structure/function relationships of polyamidoamine/DNA dendrimers as gene delivery vehicles

PAMAM dendrimers are members of a class of polyamine polymers that demonstrate significant gene delivery ability. In this study, a selection of PAMAM dendrimers, spanning a range of sizes (generations 2, 4, 7, and 9) and transfection efficiencies, are characterized by various biophysical methods to search for structural properties that correlate with transfection. Measurements of colloidal properties (size and zeta potential) as a function of charge ratio reveal that highly transfecting dendrimer/DNA complexes have size/zeta potential values between 4 and 8. Circular dichroism (CD) and FTIR spectroscopy of complexes confirm the DNA component remains in B form when associated with all dendrimer generations up to a 5:1 charge ratio (+/-). Isothermal titration calorimetry and differential scanning calorimetry detect changes that are related to polymer structure and charge ratio but do not directly correlate with transfection efficiency. Despite DNA structural and stability changes detected by CD, FTIR, DSC, and ITC that are similar to those seen with other cationic delivery vehicles [e.g., cationic lipids, peptoids/lipitoids, peptides, polyethyleneimines (PEIs), etc.], clear correlations with transfection activity are not readily apparent. This may be due, at least in part, to the heterogeneity of the complexes.