三种非病毒载体对神经母瘤细胞进行转染的效果比较

目的以增强型绿色荧光蛋白(EGFP)为报告基因,研究Lipofectamine2000、改良纳米材料CS(N/P=10)和纳米粒子PAMAM(N/P=20)介导的基因导入系统对神经母瘤细胞SH-SY5Y的毒性及基因转染效率,为神经系统疾病的基因治疗奠定基础。方法制备Lipofectamine2000、CS和PAMAM与质粒DNA(pDNA)的复合物,分别转染在体外培养的人胚肾细胞Hek293和SH-SY5Y,利用噻唑蓝(MTT)比色实验比较三种载体的细胞毒性作用、用激光共聚焦显微镜观察转染后的细胞形态、倒置荧光显微镜检测转染细胞EGFP表达强度、流式细胞仪检测转染效率。结果①Lipofectamine2000、CS和PAMAM转染细胞存活率在Hek293细胞分别为73.09%、73.69%、69.24%,三者比较无显著差异;在SH-SY5Y细胞分别为67.69%、61.71%、42.92%,前两者均显著高于后者(P均<0.05)。②Hek293细胞经Lipofectamine2000和CS与pDNA的复合物分别转染后,细胞形态均未发生明显改变,保持梭状生长;而PAMAM/pDNA复合物转染后,细胞发生皱缩,呈圆形分布生长。经三种载体转染后的SH-SY5Y细胞均发生形态改变,其中PAMAM/pDNA复合物转染者形态改变程度相对较大。Hek293细胞和SH-SY5Y细胞中,均以Lipofectamine2000/pDNA复合物转染者EGFP表达强度最大,其次为CS/pDNA复合物、PAMAM/pDNA复合物转染者。④Lipofectamine2000、CS和PAMAM的转染效率在Hek293细胞分别为60.9%、45.2%、42.7%,前者显著高于后两者(P均<0.05);在SH-SY5Y细胞分别为25.3%、19.2%、8.9%,前两者均显著高于后者(P均<0.05)。结论 Lipofectamine2000为目前最适于神经系统疾病基因治疗研究的非病毒载体;改良后的新纳米材料CS毒性比PAMAM小、转染效率比PAMAM高,有望在神经系统疾病研究中得到进一步运用。     

3种脂质体介导法转染大鼠小胶质细胞的比较研究

目的以LipofectamineTM2000为对照,研究GenEscort^TMⅠ和GenEscort^TMⅢ在大鼠小胶质细胞中的转染效率及毒性。方法分别采用LipofectamineTM2000、GenEscort^TMⅠ和GenEscort^TMⅢ为载体,转染绿色荧光蛋白（GFP）标记的siRNA进入大鼠小胶质细胞。计算转染效率。采用磺基罗丹明B法（SRB）分析转染试剂对细胞的毒性,并研究细胞传代次数、接种密度、脂质体与siRNA的比例及脂质体-siRNA复合物形成时间等对脂质体转染效率的影响。结果 2～3次细胞传代,接种密度为1×105（24孔板）、脂质体与siRNA比例为1∶2.5、脂质体-siRNA复合物形成时间分别为30 min或15 min,转染效率最高。3种不同脂质体介导的GFP-siRNA转染的大鼠小胶质细胞内均有GFP表达,其最佳转染比例下转染效率比较为LipofectamineTM2000组〉GenEscort^TMⅠ组〉GenEscort^TMⅢ组（P〈0.01）;3种转染剂的细胞毒性比较为Lipofectamine^TM2000组〉GenEscort^TMⅠ组〉GenEscort^TMⅢ组（P〈0.01）。结论阳离子脂质体GenEscort^TMⅠ比Lipofectamine^TM2000细胞毒性低,转染效率可,是一种更为理想的小胶质细胞基因转染载体。     

腈水解酶2基因沉默细胞模型的制备

目的为腈水解酶2（NIT2）基因研究奠定基础。方法采用siRNA质粒转染技术制备NIT2基因沉默细胞模型,用筛网方法从大鼠肾脏中提取出肾小球用于培养原代系膜细胞,将NIT2靶序列构建pGU6/GFP/Neo质粒中（siNIT2质粒）,采用JETPRIME脂质体转染法将质粒转染入原代系膜细胞中,48h后荧光显微镜观察转染效率,利用SYBR GREEN 1定量PCR法检测NIT2基因表达,琼脂糖凝胶电泳观察PCR产物。结果荧光显微镜下转染阳性率可达50%,定量PCR结果示siNIT2质粒转染后NIT2 mRNA显著降低,琼脂糖电泳结果示PCR产物无明显杂带。结论 siRNA质粒转染法可抑制原代系膜细胞NIT2基因的表达;为NIT2基因功能研究奠定了基础。     

日本血吸虫病新型树枝状载体-DNA疫苗的构建及其评价

[摘要] 目的构建并评价一种新型的日本血吸虫病聚酰胺-胺（PAMAM）型树枝状载体DNA疫苗。方法采用赖氨酸对4.0 G PAMAM进行表面修饰,合成端基改性产物PAMAM-Lys。用电泳阻滞实验确定质粒DNA与PAMAM-Lys复合的比例,用透射电镜测试复合物微观结构变化,并通过电泳分析复合物的稳定性。同时采用MTT法对PAMAM-Lys进行体外细胞活性评价。分别用纯化质粒pJW4303、pJW4303-SjC23、树枝状载体PAMAM-Lys和复合物PAMAM-Lys/pJW4303-SjC23免疫50只小鼠,检测各组小鼠的特异性抗体水平以评价其免疫反应性。结果 琼脂糖凝胶电泳结果显示,电荷比在2～4时,PAMAM-Lys与DNA正负电荷完全中和,DNA电泳被完全阻滞,两者能完全结合。透射电镜测试结果表明,树枝状高分子载体与DNA的复合导致DNA结构收缩,粒径减小,分布均匀。树枝状高分子与DNA复合物具有良好的稳定性。噻唑蓝法检测结果表明,改性后的树枝状高分子载体及其DNA复合物作用于293T细胞较未改性树枝状载体产生的细胞毒性低;经PAMAM-Lys/pJW4303-Sj23免疫的小鼠产生的特异性抗体水平显著高于注射裸DNA疫苗组（P<0.05）。结论 氨基酸修饰的树枝状高分子PAMAM-Lys是DNA转染的优良载体,具有良好的生物相容性,赖氨酸修饰可以显著降低PAMAM树枝状高分子的细胞毒性,并能增强DNA疫苗的免疫反应性。     

东亚钳蝎镇痛抗肿瘤肽体外靶向肝细胞癌的实验研究

背景：肝细胞癌（HCC）是全球最常见的恶性肿瘤之一,目前手术、介入、放化疗等常规治疗效果均不理想,开发有效、毒副作用相对较小的新药成为研究者关注的重点。目的：观察东亚钳蝎镇痛抗肿瘤肽（AGAP）基因真核表达载体对HCC细胞的靶向表达和毒性作用。方法：真核表达质粒pAFP．AGAP经酶切和测序鉴定后转染甲胎蛋白（AFP）阳性人HCC细胞株HepG2以及AFP阴性人宫颈癌细胞株HeLa和正常人肝细胞株LO2。逆转录聚合酶链反应（RT—PCR）检测AGAP mRNA表达,CCK-8方法检测细胞毒性作用。结果：各组细胞转染质粒pAFP-AGAP后．AGAP mRNA表达仅见于AFP阳性HepG2细胞．而AFP阴性HeLa细胞和LO2细胞均无AGAPmRNA表达。HepG2细胞转染质粒pAFP—AGAP48h后形态发生明显改变,细胞生长显著受抑（P〈0．01）．48h和72h时抑制率分别为44．4％和74．6％,而HeLa细胞和LO2细胞的形态和生长均未受明显影响。结论：AGAP基因真核表达载体可实现HCC基因治疗的靶向性和高效性,有望成为HCC靶向基因治疗的有力工具。     

TGF-β1对大鼠肝细胞系BRL-3A凋亡和细胞周期的影响

目的:研究转化生长因子β1(TGF-β1)对大鼠肝细胞系BRL-3A凋亡和细胞周期的影响.方法:MTT法检测TGF-β1对细胞增殖的影响:将BRL-3A细胞分为6组,分别给予不同浓度的TGF-β1(0、2、4、6、8、10μg/L),检测各组细胞24、36、48 h时的增殖活性;进一步将BRL-3A细胞分为TGF-β1...     

丙型肝炎病毒非结构蛋白5A调节新生多肽复合物启动子转录活性的研究

目的探讨丙型肝炎病毒（HCV）非结构蛋白5A（NS5A）对新生多肽相关复合物（NACA）启动子转录活性的影响。方法以我室构建的能够表达NS5A蛋白的pcDNA3．1（-）-NS5A质粒和含有NACA基因启动子的PCAT3-NACA报告基因质粒共转染HepG2细胞系设为实验组，同时PCAT3-NACA单独转染HepG2细胞系作为对照组。用酶联免疫吸附法检测氯霉素乙酰转移酶（CAT）的表达活性。结果pCAT3-NACA单独转染HepG2细胞的CAT酶表达活性与pCAT3-NACA和pcDNA3．1（-）-NS5A共转染组HepG2细胞的CAT酶表达活性比较，共转染组A值下降了79．3％。结论HCV NS5A能够抑制NACA启动子的活性，对NACA的表达具有下调作用。     

介入途径下中药白芨提取物作为基因递送载体的可行性

目的:探讨经介入途径中药白芨提取物作为基因递送载体的可行性.方法:从中药白芨中提取其有效成分-白芨多糖, 采用胺化还原法制备阳离子型白芨多糖,体外实验检测该阳离子型多糖对质粒DNA的结合与保护作用, 以及阳离子白芨多糖载基因复合物对肝癌细胞系HepG2的转染, 进一步通过介入途径经肝动脉给予该复合物, 以GFP作为报告基因检测复合物在体内对活体兔肝细胞的转染.结果:所制备的阳离子型白芨多糖载基因复合物可以结合并保护质粒DNA免受DNA酶的降解; 体外实验证实该复合物可以转染入体外培养肝癌细胞, 以阳离子白芨多糖作为转染载体时转染效率要低于脂质体组, 差异具有统计学意义(28.87%±3.27% vs 36.64%±6.87%,P <0.05). 采用介入方法经肝动脉给药时复合物能靶向转染入活体兔肝细胞内并实现表达.结论:采用介入途径经肝动脉给药时阳离子白芨多糖载基因复合物可以实现活体肝细胞靶向转染, 有望作为一种新型的多聚阳离子型的基因载体在基因治疗中发挥作用.     

丙型肝炎病毒NS4B对LO2肝细胞细胞周期及cyclin D1表达的影响

目的研究丙型肝炎病毒非结构蛋白4B对LO2肝细胞细胞周期和cyclinD1表达的影响，探讨HCVNS4B在HCV致病中的可能机制。方法利用脂质体介导将空白载体PCXN2及重组质粒PCXN2-NS4B转染入LO2肝细胞，G418筛选，RT-PCR法鉴定质粒转染成功。MTT法检测细胞生长并绘制生长曲线，观察NS4B对肝细胞生长的影响；流式细胞仪检测细胞周期；免疫组化法检测细胞cyclinD1的表达。结果NS4B成功转染入LO2细胞；转染的NS4B可促进肝细胞的生长；转染PcxN2-NS4B细胞的S期、G2／M期较转染PCXN2细胞增加，两组比较差异有显著性（P〈0．05）；转染NS4B的细胞cyclinD1表达较转染空白载体组增强，两组比较差异有显著性（P〈0．01）。结论 HCVNS4B可能通过调节某些基因转录与表达，促进DNA合成，干扰肝细胞周期，促进肝细胞增殖。     

人STIM1基因真核表达载体的构建及其在肝细胞中的表达

目的: 构建人STIM1基因真核表达载体, 并观察其在人肝细胞株(HL-7702)中的表达.方法: 提取HL-7702细胞总RNA, RT-PCR扩增,经纯化回收后将片段克隆至pGM-T载体, 酶切琼脂糖凝胶电泳分析鉴定并测序, 最后用重组质粒转染HL-7702细胞, 通过PCR-电泳和Western blot法检测STIM1基因的表达.结果: PCR扩增的片段长度为342 bp, 测序结果以及重组质粒pGM-T-STIM1的酶切琼脂糖凝胶电泳鉴定结果均证明STIM1基因成功克隆到真核表达载体中. PCR-电泳和Westernb l o t实验结果分别显示转染重组质粒后的HL-7702细胞在基因与蛋白水平表达STIM1均有所增强.结论: 成功构建了人STIM1基因的真核表达载体pGM-T-STIM1, 并在人肝细胞株HL-7702中稳定表达, 为研究STIM1蛋白在人肝细胞内Ca2+浓度调控方面及其对人肝细胞分泌功能的影响奠定了良好的实验基础.     

The construction of a novel kind of non-viral gene delivery vector based on protein as core backbone

Background and Objectives   A novel kind of non-viral gene delivery vector based on transferrin (Tf) as the core component was constructed with high transfection efficiency and low toxicity.
Materials and Methods   The synthesis vector of Tf-PEI600 was confirmed by different physicochemical methods, including ¹H nuclear magnetic resonance, gel permeation chromatography, X-ray and thermogravimetric analysis. The cytotoxicity and gene delivery efficiency of the synthesized vector were verified by in vitro experiments.
Results   The agarose gel electrophoresis assay indicated that the novel copolymer Tf-PEI600 could efficiently condense plasmid DNA and the condensed nanoparticles exhibited a spherical shape. As the weight ratio of Tf-PEI600 to DNA reached 15·0, the particle size (about 200 nm) and the zeta potential (about 20 mV) of the nanoparticles became optimal for gene delivery. The methylthiazolyl tetrazolium (MTT) assay showed the cytotoxicity of Tf-PEI600 to be similar to that of PEI600 and much lower than that of PEI25kDa. In gene-delivery experiments with COS-7 cells and HepG2 cells, the Tf-PEI600 showed about a 30- to 53-fold higher efficiency than PEI600 and nearly equal to that of PEI25kDa.
Conclusions   These data suggest that Tf-PEI600, with the advantages of low toxicity and high gene-delivery efficiency, might have great prospects in the practice of gene delivery. The core-shell structure of Tf-PEI600 also provided a novel strategy for the construction of non-viral gene delivery vectors.     

Enhancing polyethylenimine's delivery of plasmid DNA into mammalian cells

The effect of various chemical modifications of nitrogen atoms on the efficiency of polyethylenimines (PEIs) as synthetic vectors for the delivery of plasmid DNA into monkey kidney cells in vitro has been systematically investigated. The resultant structure-activity relationship has both provided mechanistic insights and led to PEI derivatives with markedly enhanced performance. For example, N-acylation of PEI with the molecular mass of 25 kDa (PEI25, one of the most potent polycationic gene delivery vectors) with alanine nearly doubles its transfection efficiency in the presence of serum and also lowers its toxicity. Furthermore, dodecylation of primary amino groups of 2-kDa PEI yields a nontoxic polycation whose transfection efficiency in the presence of serum is 400 times higher than the parent's and which exceeds 5-fold even that of PEI25.     

Conjugation to gold nanoparticles enhances polyethylenimine's transfer of plasmid DNA into mammalian cells

Branched polyethylenimine (PEI) chains with an average molecular mass of 2 kDa (PEI2) have been covalently attached to gold nanoparticles (GNPs), and the potency of the resulting PEI2-GNPs conjugates as vectors for the delivery of plasmid DNA into monkey kidney (COS-7) cells in the presence of serum in vitro has been systematically investigated. The transfection efficiencies vary as a function of the PEI/gold molar ratio in the conjugates, with the best one (PEI2-GNPII) being 12 times more potent than the unmodified polycation. This potency can be further doubled by adding amphiphilic N-dodecyl-PEI2 during complex formation with DNA. The resulting ternary complexes are at least 1 order of magnitude more efficient than the 25-kDa PEI, one of the premier polycationic gene-delivery vectors. Importantly, although unmodified PEI2 transfects just 4% of the cells, PEI2-GNPII transfects 25%, and the PEI2-GNPII/dodecyl-PEI2 ternary complex transfects 50% of the cells. The intracellular trafficking of the DNA complexes of these vectors, monitored by transmission electron microscopy, has detected the complexes in the nucleus <1 h after transfection.     

Comparison of chitosan,alginate and chitosan/alginate nanoparticles with respect to their size,stability, toxicity and transfection

ObjectiveTo to compare the chitosan/alginate, chitosan and alginate nanoparticles as plasmid vectors, to determine the morphological characteristics, size and physicochemical properties of nanoparticle-pEGFP complexes and to evaluate the potential of these nanoparticles in transfection of pEGFP plasmid in to a cultured the human embryonic kidney cell line (HEK 293 cells).MethodsNanoparticles comprising chitosan, alginate and both chitosan-alginate polymers were formed through pregel preparation method. The ability of plasmid-complexes in preventing DNA migration were assessed by the agarose gel assay. The efficiency of nanoparticles in transfection of pEGFP plasmid in the cultured HEK 293 cells was measured by flow cytometry. The effect of the nanoparticle-plasmid complexes on the cell viability was determined using cytotoxicity assay.ResutlsChitosan, alginate and alginate/chitosan nanoparticles had a mean Z-average diameter of 620 nm, 235.8 nm and 161.8 nm and mean zeta potential of 45 mV, −18.6 mV and 29.3 mV, respectively. Chitosan and chitosan/alginate nanoparticles have greater capacity to maintain plasmid than alginate nanoparticles. Alginate nanoparticles had the greater transfection in comparison to the others. Cell viability assays indicated that nanoparticles had no toxic effect on HEK 293 cells after 4 h or 24 h.ConclusionsThe combination of particle surface, hydrophobicity size and zeta potential can influence on transfection efficiency and the cellular uptake of the nanoparticles. Our suitable candidate for gene delivery would be alginate/chitosan nanoparticles.     

Magnetofection potentiates gene delivery to cultured endothelial cells

Modification of cellular functions by overexpression of genes is increasingly practised for research of signalling pathways, but restricted by limitations of low efficiency. We investigated whether the novel technique of magnetofection (MF) could enhance gene transfer to cultured primary endothelial cells. MF of human umbilical vein endothelial cells (HUVEC) increased transfection efficiency of a luciferase reporter gene up to 360-fold compared to various conventional transfection systems. In contrast, there was only an up to 1.6-fold increase in toxicity caused by MF suggesting that the advantages of MF outbalanced the increase in toxicity. MF efficiently increased transfection efficiency using several commercially available cationic lipid transfection reagents and polyethyleneimine (PEI). Using PEI, even confluent HUVEC could be efficiently transfected to express luciferase activity. Using a green fluorescent protein vector maximum percentages of transfected cells amounted up to 38.7% while PEI without MF resulted in only 1.3% transfected cells. Likewise, in porcine aortic endothelial cells MF increased expression of a luciferase or a beta-galactosidase reporter, reaching an efficiency of 37.5% of cells. MF is an effective tool for pDNA transfection of endothelial cells allowing high efficiencies. It may be of great use for investigating protein function in cell culture experiments.     

有效抑制小鼠小胶质细胞上Toll样受体9表达的siRNA的筛选

目的：筛选有效抑制小鼠小胶质细胞（BV-2细胞）上Toll样受体9（TLR9）表达的小干扰RNA（siRNA）序列,并检测转染复合物的细胞毒性。方法设计并合成针对TLR9的3对siRNA（siRNA-836、siRNA-1549和siRNA-2410）及一条带绿色荧光标记（FAM）的通用阴性对照FAM-siRNA。在X-tremeGENEsiRNA转染试剂介导下转染BV-2细胞。倒置荧光显微镜下观察转染后BV-2细胞FAM-siRNA的分布,流式细胞仪检测转染效率,q-PCR检测TLR9的mRNA表达,Westernblot检测TLR9蛋白的表达,并比较其抑制率,筛选出有效抑制靶基因表达的siRNA。CCK-8检测细胞存活率的变化。结果BV-2细胞转染FAM-siRNA后6h,胞质内可见绿色荧光分布。FAM-siRNA表达阳性率为（91.87±4.77）％。转染TLR9siRNA后,BV-2细胞中TLR9mRNA表达明显下降。与阴性对照组及序列siRNA-836、siRNA-2410相比,序列siRNA-1549的TLR9沉默效能最高,使BV-2细胞上TLR9mRNA表达于24h和48h分别降低（77.89±4.23）％和（65.36±11.07）％,TLR9蛋白表达分别下降（48.37±20.56）％和（44.30±14.31）％。CCK-8检测TLR9siRNA转染组与对照组相应时间点比较,BV-2细胞存活率无明显变化（P＞0.05）。结论序列siRNA-1549对BV-2细胞上TLR9表达的抑制效果最大,利用RNA干扰处理BV-2细胞,对细胞基本无毒性作用。     

肝动脉化疗栓塞同步经皮肝穿瘤内无水乙醇注射治疗原发性肝癌

目的 探讨肝动脉化疗栓塞术（TACE）在超声及数字血管造影机（DSA）监视下行经皮肝穿瘤内无水乙醇注射（PEI）治疗原发性肝癌（PLC）的安全性及疗效。方法 选择57例PLC患者随机分为联合治疗组（TACE＋PEI）30例和对照组（单纯TACE）27例。联合治疗组在DSA下行TACE术后即刻在超声及DSA引导下细针PEI。对照组行常规TACE治疗。结果 联合治疗组在超声及DSA引导下全部精准穿刺靶点,术中中等疼痛18例,无其他严重不良反应,其术后发热、肝肾功能、血常规、PT等指标与对照组比较,差异均无统计学意义（P均〉0.05）,57例患者均无严重并发症出现。联合治疗组有效率为83.3%（25/30）,对照组为55.6%（15/27）;联合治疗组1年生存率为86.7%,对照组为63%,两组比较差异均有统计学意义（P〈0.05）。结论 肝动脉化疗栓塞同时行PEI治疗PLC安全性较好,其1年生存率优于单纯TACE治疗者。     

旋毛虫与伪旋毛虫肌幼虫抗原的SDS-PAGE和双向电泳分析

目的鉴定旋毛虫(Trichinella spiralis,T1)与伪旋毛虫(T.pseudospiralis,T4)肌幼虫的差异蛋白。方法应用SDS-PAGE和双向电泳(two-dimensional gel electrophoresis,2-DE)对T1、T4肌幼虫的可溶性抗原与培养24h的ES抗原的蛋白组分进行分析。结果SDS-PAGE显示,T1肌幼虫可溶性抗原有22条蛋白带(221.62kDa～14.88kDa),其中6条为T1特异性蛋白带(59.72、44.37、23.66、22.36、18.26、16.34kDa);T4可溶性抗原蛋白有18条带(185.28kDa～14.27kDa),其中4条为T4特异性蛋白带(132.60、119.30、35.26、31.02kDa)。T1的ES抗原有10条蛋白带(113.21kDa～14.37kDa),T4的ES抗原有9条蛋白带(104.71kDa～14.51kDa),T1、T4肌幼虫ES抗原的蛋白带均不相同。2-DE显示,T1可溶性抗原有193±12个蛋白点,分子量主要为11kDa～22kDa、25kDa～64kDa及100kDa～144kDa,所对应的等电点(pI)分别为4.7～8.2、4.5～6.5及5～7;T4可溶性抗原有175±9个蛋白点,分子量主要为12kDa～21kDa及25kDa～90kDa,所对应的pI分别为4～9.5与4.5～9.6。T1的ES抗原具有82±6个蛋白点,分子量主要为13kDa～16kDa、18kDa～22kDa及40kDa～55kDa,所对应的pI分别为4～7、3.8～6.2及5～9;T4的ES抗原具有69±5个蛋白点,分子量主要为10kDa～15kDa、17kDa～25kDa及29kDa～55kDa,所对应的pI分别为4.7～6.5、4.6～6及5～7。结论旋毛虫肌幼虫可溶性抗原及ES抗原的蛋白组分与伪旋毛虫的明显不同。     

A versatile vector for gene and oligonucleotide transfer into cells in culture and in vivo: polyethylenimine.

Several polycations possessing substantial buffering capacity below physiological pH, such as lipopolyamines and polyamidoamine polymers, are efficient transfection agents per se--i.e., without the addition of cell targeting or membrane-disruption agents. This observation led us to test the cationic polymer polyethylenimine (PEI) for its gene-delivery potential. Indeed, every third atom of PEI is a protonable amino nitrogen atom, which makes the polymeric network an effective "proton sponge" at virtually any pH. Luciferase reporter gene transfer with this polycation into a variety of cell lines and primary cells gave results comparable to, or even better than, lipopolyamines. Cytotoxicity was low and seen only at concentrations well above those required for optimal transfection. Delivery of oligonucleotides into embryonic neurons was followed by using a fluorescent probe. Virtually all neurons showed nuclear labeling, with no toxic effects. The optimal PEI cation/anion balance for in vitro transfection is only slightly on the cationic side, which is advantageous for in vivo delivery. Indeed, intracerebral luciferase gene transfer into newborn mice gave results comparable (for a given amount of DNA) to the in vitro transfection of primary rat brain endothelial cells or chicken embryonic neurons. Together, these properties make PEI a promising vector for gene therapy and an outstanding core for the design of more sophisticated devices. Our hypothesis is that its efficiency relies on extensive lysosome buffering that protects DNA from nuclease degradation, and consequent lysosomal swelling and rupture that provide an escape mechanism for the PEI/DNA particles.