Gene transfer into hepatoma cells mediated by galactose-modified alpha-helical peptides

To develop a receptor-mediated gene delivery system into hepatoma cells using the cationic alpha-helical peptide as the gene carrier molecule, we modified an alpha-helical peptide, which is known to have transfection abilities into cells, with a multi-antennary ligand containing several galactose residues that provide efficient binding to the asialoglycoprotein receptor. The galactose-modified peptides formed complexes with a plasmid DNA and showed gene transfer abilities into HuH-7 cells, a human hepatoma cell line. The transfection efficiency of the peptide was increased by increasing the number of modified galactose residues on the peptide. Furthermore, considerable inhibition of the transfection efficiency by the addition of asialofetuin, which is a ligand for the asialoglycoprotein receptor, was observed in all galactose-modified peptides. Based on this result, we could confirm that the internalization of the galactose-modified peptides occurred by the receptor-mediated endocytosis pathway. In addition, to understand the transport route of the peptide-DNA complex in the cell, the effects on the transfection efficiencies with several endocytosis inhibitors were examined. As a result, it was suggested that the translocation of the peptide-DNA complex from the endocytic compartments to the cytosol mainly occurred during an early endosome step.     

Mannose Receptor-Mediated Gene Delivery into Antigen Presenting Dendritic Cells

Dendritic cells are professional antigen presenting cells and are unique in their ability to prime naíve T cells. Gene modification of dendritic cells is of particular interest for immunotherapy of diseases where the immune system has failed or is aberrantly regulated, such as in cancer or autoimmune disease, respectively. Dendritic cells abundantly express mannose receptor and mannose receptor-related receptors, and receptor-mediated gene transfer via mannose receptor offers a versatile tool for targeted gene delivery into these cells. Accordingly, mannose polyethylenimine DNA transfer complexes were generated and used for gene delivery into dendritic cells. Mannose receptor belongs to the group of scavenger receptors that allow dendritic cells to take up pathogenic material, which is directed for degradation and MHC class II presentation. Therefore, a limiting step of transgene expression by mannose receptor-mediated gene delivery is endosomal degradation of DNA. Several strategies have been explored to overcome this limitation including the addition of endosomolytic components to DNA transfer complexes like adenovirus particles and influenza peptides. Here, we review the current understanding of mannose receptor-mediated gene delivery into dendritic cells and discuss strategies to identify appropriate endosomolytic agents to improve DNA transfer efficacy.     

通过受体介导法将核酶特异导入肝细胞以阻断HBV…

应用半乳糖末端糖蛋白受体介导的内吞作用，将外源基因导入真核细胞，与脂质体介导的传染和细胞表面转锪蛋白受介导的内吴作用相比，虽然三种方式均能有效介导外源基因的转移，但ＡＳＧＰ－Ｒ法具有肝细胞特异性，而脂质体法和Ｔｒ－Ｒ法不具此特性。将克隆于真核表达载体的针对乙型肝炎病毒ｍＲＮＡＰｒｅＣ／Ｃ区的核酶质粒ｐＣＭＶ－Ｒｉｐｃ特异性导入肝细胞 并发挥作用，通过酶联免疫吸附法检测细胞培养液中的乙型肝炎表现抗原     

通过受体介导法将核酶特异导入肝细胞以阻断HBV蛋白表达的初步研究

应用半乳糖末端糖蛋白受体（ＡＳＧＰ－Ｒ）介导的内吞作用，将外源基因导入真核细胞，与脂质体介导的转染和细胞表面转铁蛋白受体（Ｔｆ－Ｒ）介导的内吞作用相比，虽然三种方式均能有效介导外源基因的转移，但ＡＳＧＰ－Ｒ法具有肝细胞特异性，而脂质体法和Ｔｆ－Ｒ法不具此特性。将克隆于真核表达载体的针对乙型肝炎病毒（ＨＢＶ）ｍＲＮＡＰｒｅＣ／Ｃ区的核酶质粒ｐＣＭＶ－Ｒｉｐｃ特异性导入肝细胞并发挥作用，通过酶联免疫吸附法（ＥＬＩＳＡ）检测细胞培养液中的乙型肝炎表面抗原（ＨＢｓＡｇ）和ｅ抗原（ＨＢｅＡｇ），评价核酶在细胞水平对ＨＢＶ抗原表达的阻断作用。结果表明当核酶质粒ｐＣＭＶ－Ｒｉｐｃ与ＨＢＶ抗原表达质粒ｐＵＣ－２ＨＢＶ共转染ＨｅｐＧ２细胞时，核酶对ＨＢｓＡｇ和ＨＢｅＡｇ表达的抑制率分别为５５．２９％和６８．７３％。     

大鼠IL-10基因真核表达质粒的构建及其在BRL细胞中的表达

目的:构建大鼠IL-10基因的真核表达载体,观察其在大鼠肝细胞系BRL中的表达,比较有无受体介导的脂质体的转染效率.方法:抽提外周血单个核细胞的总RNA,通过RT-巢式PCR方法获得大鼠IL-10的全长编码序列,定向克隆到真核表达载体pcDNA3.0,并进行限制性内切酶酶切及测序鉴定.将重组质粒分别通过脂质体TransfastTM与去唾液酸糖蛋白受体介导的脂质体PEIjet-gal转入大鼠肝细胞系BRL,通过RT-PCR方法检测IL-10 mRNA的表达,比较二者的转染效率,用ELISA法检测后者分泌型IL-10的表达.结果:经酶切及测序鉴定证实,重组质粒插入片段与大鼠IL-10的全长编码序列完全相符.发现受体介导的脂质体PEIjet-gal转染效率明显高于非受体介导的脂质体TransfastTM .通过受体介导的脂质体转染,BRL细胞获得高水平的IL-10表达.结论:成功地构建pcDNA3.0-IL-10重组质粒.受体介导的脂质体对肝细胞有较高的转染活性,可能成为IL-10基因治疗肝纤维化的有效转染载体.     

Adhesion contact dynamics of HepG2 cells on galactose-immobilized substrates

The specific recognition between asialoglycoprotein receptor and galactose ligand at cell-substrate interfaces has been shown to mediate hepatocyte adhesion and maintain liver specific functions of hepatocytes. Conventionally, the success of hepatocyte attachment on engineered tissue scaffold is inferred from the degree of two-dimensional cell spreading that is measured by transmitted light microscopy. However, the actual contact mechanics and adhesion strength of hepatocytes during two-dimensional cell spreading has not been elucidated due to lack of biophysical probe. In this study, a novel biophysical technique known as confocal reflectance interference contrast microscopy (C-RICM) in conjunction with phase contrast microscopy is utilized to probe the adhesion dynamics, contact mechanics and two-dimensional spreading kinetics of HepG2 cells on galactose immobilized and collagen gel coated substrates. C-RICM demonstrates that HepG2 cells form strong adhesion contacts with both galactose-immobilized surfaces and collagen gel coated substrates. Moreover, HepG2 cells maintain their compact shapes in the presence of asialoglycoprotein receptor-mediated recognition while they become exceedingly spread under integrin-mediated adhesion on collagen gel coated substrate. The initial rate of adhesion contact formation and the steady-state adhesion energy of HepG2 cell population are highest on substrate conjugated with galactose ligand via a longer spacer. The adhesion dynamics and final adhesion energy of HepG2 cells depends both on the type of ligand-receptor interaction and the length of spacer between the ligand and substrate. Most importantly, new biophysical insights into the initial hepatocyte attachment that are critical for hepatocyte culture are provided through the decomposition of two-dimensional spreading and adhesion contact formation on bio-functional substrates.     

Mannan-mediated gene delivery for cancer immunotherapy

Recent years have seen a resurgence in interest in the development of efficient non-viral delivery systems for DNA vaccines and gene therapy. We have previously used oxidized and reduced mannan as carriers for protein delivery to antigen-presenting cells by targeting the receptors that bind mannose, resulting in efficient induction of cellular responses. In the present study, oxidized mannan and reduced mannan were used as receptor-mediated gene transfer ligands for cancer immunotherapy. In vivo studies in C57BL/6 mice showed that injection of DNA encoding ovalbumin (OVA) complexed to oxidized or reduced mannan-poly-L-lysine induced CD8 and CD4 T-cell responses as well as antibody responses leading to protection of mice from OVA+ tumours. Both oxidized and reduced mannan delivery was superior to DNA alone or DNA-poly-L-lysine. These studies demonstrate the potential of oxidized and reduced mannan for efficient receptor-mediated gene delivery in vivo, particularly as DNA vaccines for cancer immunotherapy.     

Thyroid hormone (T3)-modification of polyethyleneglycol (PEG)-polyethyleneimine (PEI) graft copolymers for improved gene delivery to hepatocytes

Targeting of gene vectors to liver hepatocytes could offer the opportunity to cure various acquired and inherited diseases. Efficient gene delivery to the liver parenchyma has been obscured from efficient targeting of hepatocytes. Here we show that the thyroid hormone, triiodothyronine (T3), can be used to improve the gene transfer efficiency of nonviral gene vectors to hepatocytes in vitro and to the liver of mice in vivo. T3 conjugated to the distal ends of fluorescent labeled PEG-g-dextran resulted in T3-specific cellular endosomal uptake into the hepatocellular cell line HepG2. PEG-g-PEI graft copolymers with increasing molar PEG-ratios were synthesized, complexed with plasmid DNA, and transfected into HepG2 or HeLa cells. Gene transfer efficiency decreased as the number of PEG blocks increased. T3 conjugation to PEI and the distal ends of PEG blocks resulted in T3 specific gene transfer in HepG2 cells as evidenced by reduction of gene transfer efficiency after pre-incubation of cells with excess of T3. In vivo application of T3-PEG-g-PEI based gene vectors in mice after tail vein injection resulted in a significantly 7-fold increase of gene expression in the liver compared with PEG-g-PEI based gene vectors.     

A lipooligosaccharide-binding site on HepG2 cells similar to the gonococcal opacity-associated surface protein Opa.

The lacto-N-neotetraose-containing lipooligosaccharide (LOS) present on the surface of most Neisseria gonorrhoeae organisms may serve many important functions in gonococcal pathogenesis. This surface glycolipid contains the cross-reactive epitope to human paragloboside and can be sialylated by gonococci grown in the presence of CMP-N-acetylneuraminic acid. Another possible role for this glycolipid could be to mimic human asialocarbohydrates and act as a ligand for asialoglycoprotein receptors contained on numerous human cells. The most noted of this large family of receptors is that expressed on the surface of hepatic cells. In a model cell system, using the hepatoma tissue culture cell line HepG2, we wanted to investigate if the presence of this asialoglycoprotein receptor influenced the adherence and/or invasion of gonococci expressing the lacto-N-neotetraose structure. Piliated variants of the gonococcal wild-type strain 1291 and its isogeneic LOS mutant 1291E were used in adherence-invasion assays. This gonococcal strain is somewhat unusual in that it expresses large amounts of predominantly one species of LOS, thus reducing the complexity of interpreting the data. The data from these assays suggested that the Gal(beta 1-4)GlcNAc(beta 1-3)Gal(beta 1-4)Glc carbohydrate structure on the wild-type LOS affected the adherence-invasion of gonococci into the HepG2 cells. In studies to determine whether the major hepatic asialoglycoprotein receptor was involved in these interactions, we found that the HepG2 cells contained two receptors which bound gonococcal LOS. One of these was the asialoglycoprotein receptor, and the data concerning this receptor will be reported elsewhere. The data on the second receptor are reported here. Purified, 125I-labeled gonococcal LOS was used to identify specific high-affinity LOS-binding sites. These binding experiments revealed one major binding site corresponding to a protein with a molecular mass of 70 kDa (p70). Several lines of evidence in this study suggested that the oligosaccharide region of LOS played an important role in LOS binding to the p70 of HepG2 cells. In addition, we show that this human LOS receptor has some similarities to the gonococcal Opa proteins.     

The role of adenosine receptor and caveolae-mediated endocytosis in oligonucleotide-mediated gene transfer

We previously reported the preparation and characterization of ternary nanoparticles with the negative surface charge, which comprises histidine-conjugated polyallylamine (PAA-HIS)/DNA core complex and a single-stranded oligonucleotide outer layer, to transfect various cell lines. As a continued effort, here the investigations on the endocytotic mechanisms involved in the uptake of the oligonucleotide-coated PAA-HIS/DNA complexes are reported. Interestingly, these complexes showed enhanced transfection efficiency only when deoxyadenosine-containing oligonucleotides were deposited on the PAA-HIS/DNA complex surface. The addition of uncomplexed oligonucleotide, free adenosine and adenosine receptor antagonist significantly inhibited the transfection efficiency of oligonucleotide-coated PAA-HIS/DNA complexes. These results indicated that the oligonucleotide-coated PAA-HIS/DNA complexes could specifically recognize adenosine receptors on the cell surface and were taken up by adenosine receptor-mediated process. Uptake and transfection experiments with various endocytic inhibitors suggested that, after receptor/ligand binding, oligonucleotide-coated PAA-HIS/DNA/complexes were mainly internalized via caveolae-mediated pathway to result in effective intracellular processing for gene expression. In conclusion, both adenosine receptor and caveolae-mediated endocytosis play important roles in oligonucleotide-mediated gene transfer.     

Gene transfer to respiratory epithelial cells via the receptor-mediated endocytosis pathway.

Gene-based therapies for a variety of inherited and acquired pulmonary diseases will require the development of vectors capable of safe and efficient transfer of DNA to the respiratory epithelium. The present study examined the feasibility of delivering DNA to respiratory epithelial cells by the receptor-mediated endocytosis pathway. This strategy employs molecular conjugates consisting of a cognate moiety, in this case human transferrin, covalently linked to a DNA-binding moiety, such as a cationic polyamine. Complexes were formed between transferrin-polylysine conjugates (hTfpL) and plasmid DNA carrying the firefly luciferase reporter gene (pRSVL). The conjugate-DNA complexes were added directly to cells in tissue culture and incubated for 24 h, after which cell lysates were analyzed for luciferase enzyme activity by luminometry. An immortalized human respiratory epithelial cell line (HBE1) treated with the transferrin-polylysine-DNA complexes exhibited luciferase enzyme activity significantly augmented over background levels. This respiratory epithelial cell line exhibited greater susceptibility to gene transfer by the transferrin-polylysine conjugates than did non-respiratory epithelial cell lines known to possess high levels of transferrin receptors. Effective gene transfer was shown to require both the DNA-binding moiety and cognate moiety for the cell surface receptor. Specific internalization of the conjugates by the transferrin pathway was verified by competition for the transferrin receptor. In addition, treatment with agents that either increased transferrin receptor number or decreased lysosomal degradation markedly augmented gene expression mediated by the conjugates. Thus, respiratory epithelial cells possess receptors for transferrin that can be exploited to accomplish gene transfer by the receptor-mediated endocytosis pathway.     

Enhanced gene delivery to PC12 cells by a cationic polypeptide

Targeted gene delivery to diseased subtypes of neurons will be beneficial to the success of gene therapy of neurological disorders. We designed a recombinant cationic polypeptide to facilitate gene delivery to neuronal-like PC12 cells that express the nerve growth factor (NGF) receptors. The recombinant polypeptide was composed of a targeting moiety derived from loop 4-containing hairpin motif of NGF and a DNA-binding moiety of 10-lysine sequence and expressed in Escherichia coli. It activated NGF receptor, TrkA and its downstream signaling pathways in PC12 and promoted the survival of neuronally differentiated PC12 cells deprived of serum. The polypeptide could also bind plasmid DNA and enhance polycation-mediated gene delivery in NGF receptor-expressing PC12 cells, but not in COS7 cells lacking NGF receptors. The enhancement of gene transfer in PC12 was inhibited by pretreatment of free, unbound polypeptides, suggesting a NGF-receptor-specific effect of the polypeptide. These observations demonstrated the concept of using receptor-mediated mechanism for targeted gene delivery to neurons.     

A biocleavable pullulan-based vector via ATRP for liver cell-targeting gene delivery

Pullulan due to its specificity for liver has been widely exploited for biomedical applications. In this work, a tailor-made biocleavable pullulan-based gene vector (PuPGEA) with good hemocompatibility was successfully proposed via atom transfer radical polymerization (ATRP) for efficient liver cell-targeting gene delivery. A two-step method involving the reaction of hydroxyl groups of pullulan with cystamine was developed to introduce reduction-sensitive disulfide-linked initiation sites of ATRP onto pullulan. The poly(glycidyl methacrylate) (PGMA) side chains prepared subsequently via ATRP were functionalized with ethanolamine (EA) to produce the resultant biocleavable comb-shaped PuPGEA vectors consisting of nonionic pullulan backbones and disulfide-linked cationic EA-functionalized PGMA (PGEA) side chains with plentiful secondary amine and nonionic hydroxyl units. The cationic PGEA side chains can be readily cleavable from the pullulan backbones of PuPGEA under reducible conditions. Due to the liver targeting performance of pullulan backbones, such PuPGEA vectors exhibited much higher gene transfection efficiency and cellular uptake rates in HepG2 cell lines than in Hella cell lines. In addition, in vitro transfection efficiency and uptake mechanism of polyplex in HepG2 cells were evaluated in the presence of different endocytosis inhibitors, indicating that the asialoglycoprotein receptor was involved in transfection process of hepatocytes. More importantly, in comparison with gold standard polyethylenimine (PEI, ∼25 kDa), PuPGEA vectors possessed excellent hemocompatibility without causing undesirable hemolysis. Properly grafting short bioreducible PGEA polycation side chains from a liver cell-targeting pullulan backbone is an effective means to produce new hemocompatible polysaccharide-based gene delivery vectors.     

Novel receptor-mediated gene delivery system comprising plasmid/protamine/sugar-containing polyanion ternary complex

Poly(ethylene glycol) (PEG) derivative having both carboxylic acid-, and lactose-side chains (Lac-PEG-C) deposited onto the surface of DNA/protamine (PRT) complex, and the self-assembled ternary complex was obtained. The diameter of the complexes was 180-200 nm, and they showed good size stability even in the high ionic strength solutions. Lac-PEG-C coating reduced their surface electric potential, and effectively avoided the albumin-induced aggregation. DNA/PRT/Lac-PEG-C complex did not coagulate the red blood cells, and their cytotoxicity evaluated by WST-1 was very low. Lac-PEG-C added to the plasmid/PRT complex prior to the incubation with HepG2 cells extremely enhanced the gene-expression, and by the plasmid/PRT/Lac-PEG-C complex prepared at 1:1.5:8 in weight, 56-fold higher expression of luciferase than that without Lac-PEG-C was observed. The treatment with asialofetuin or phenylarsine oxide evidently interfered with the gene-expression. The high gene expression by the plasmid/PRT/Lac-PEG-C ternary complex on the hepatocyte would be attributed to the asialoglycoprotein receptor-mediated endocytosis.     

Hydrophobic poly (amino acid)-modified PEI-mediated delivery of single-chain antibody scFv1C9 inhibits HepG2 cell cycle process and xenograft growth in nude mice

The safe and effective gene delivery vector remains the key step for gene therapy. Hydrophobic-modified Phe-PEI (PP80) was exhibited in advantage with biocompatibility and gene delivery with smaller size and easier penetration into cells and tissues. PP80 delivery of rev-casp-3 gene was demonstrated effectively to inhibit HeLa xenograft growth in our previous work. However, it was necessary to evaluate its applicability in other cells or tissues as gene carrier. Here, we quantitatively optimized the complex ratio of PP80 and plasmid DNA (pDNA) and evaluated the potential pyrogenicity by rabbit pyrogen test. In addition, PP80-mediated expression of scFv1C9 gene blocked HepG2 cell cycle progress in vitro. Subsequently, PP80-scFv1C9 was injected into HepG2 xenograft and significantly inhibited the xenograft growth in nude mice. Further investigation indicated that PP80 was an effective gene carrier and possible for entering hepatic xenograft. These features of PP80 made it attractive as a potential gene carrier for cancer therapy.     

脂质体介导的p53基因对肝癌细胞生长的抑制作用

目的 观察外源野生型ｐ５３基因在肝癌基因治疗方面的可行性。方法 将载有人野生型ｐ５３－ｃＤＮＡ的真核表达质粒ｐ５３－ｐｃＤＮＡ３,用阳离子脂质体介导转染人肝癌细胞系ＨｅｐＧ２,用流式细胞仪检测ｐ５３－ｐｃＤＮＡ３对ＨｅｐＧ２细胞生长的影响。结果 通过观察细胞生长曲线与流式细胞仪检测细胞周期和细胞的凋亡指数发现,ＨｅｐＧ２细胞生长受到明显的抑制。结论 脂质体介导的ｐ５３基因可在Ｈ细胞中表达,且明显抑     

Stimulation of Histamine Receptors of Human Monocytoid and Hepatoma-Derived Cell Lines and Mouse Hepatocytes Modulates the Production of the Complement Components C3, C4, Factor B, and C2

The influence of histamine (and the related agonists and antagonists) alone or in the presence of recombinant human interleukin 1 alpha (IL-1 alpha) and gamma interferon (IFN-gamma) was studied on the production of complement components C3, C2, factor B, and C4 in vitro with human monocytoid cell line U937, hepatoma-derived cell line HepG2, and mouse hepatocytes. Both U937 and HepG2 cells responded to histamine through H1 and H2 histamine receptors. The effect of histamine on the biosynthesis and gene expression of complement proteins was predominantly enhancing via the H1 histamine receptors and inhibitory through the H2 receptors. The actual predominance of the histamine receptor involved (and the outcome of the ligand interaction) seemed to be greatly affected by the simultaneous activation of the cells by IL-1 or IFN-gamma.     

乳糖化多聚赖氨酸导向反义寡核苷酸抗乙型肝炎病毒的作用

目的 研究乳糖化多聚赖氨酸（Gal-PLL）导向反义寡核苷酸对乙型肝炎病毒（HBV）基因表达的特异性抑制作用。方法 根据聚合酶链反应（PCR）产物直接测序结果,在HBV U5样序列区合成了一段16聚硫代磷酸的反义寡核苷酸,并将其与肝靶向配体GaL-PLL连接,在2.2.15细胞比较,观察了它们对HBV基因表达的影响,结果 通过测序确定了2.2.15细胞中的HBV DNA属于HBV表面抗原ayw1亚型,并将此用于反义寡核苷酸的序列设计;经荧光组化分析表明,Gal-PLL对大鼠肝组织有选择性亲和力;Gal-PLL与DNA形成复合物的最佳摩尔比为2：1,在相同实验条件下,硫代磷酸反义寡核苷酸对HBsAg和HBeAg的抑制率分别为70％和58％,而Gal-PLL硫代磷酸反义寡核苷酸对HBsAg和HBeAg的抑制率分别为96％和82％,同时培养上清液和细胞中HBV DNA的含量明显下降,无关序列寡核酸无明显效果,寡核苷酸对细胞未产生毒性,结论 肝靶向配体和反义寡核酸的复合物可以通过无唾液酸糖蛋白受体靶入2.2.15细胞内,并对HBV基因表达和复制产生特异性抑制作用。     

A gene nanocomplex conjugated with monoclonal antibodies for targeted therapy of hepatocellular carcinoma

To enhance tumor-targeting abilities and therapeutic efficiency, a monoclonal antibody-conjugated gene nanocomplex was herein designed. The biodegradable cationic polyethylenimine-grafted-α,β-poly(N-3-hydroxypropyl)-DL-aspartamide (PHPA-PEI) was used for complexing pDNA to form the PHPA-PEI/pDNA nanoparticle, and then 9B9 mAb, an anti-epidermal growth factor receptor (anti-EGFR) monoclonal antibody, was conjugated to produce the PHPA-PEI/pDNA/9B9 mAb (PP9mN) complex. The PP9mN complex with the diameter of around 300 nm at its optimal weight ratio could be uptaken effectively by SMMC-7721 cells. The cytotoxicity of the PP9mN complex was much lower than that of PEI 25 kD in SMMC-7721, HepG2, Bel-7404 and COS-7 cell lines. The PP9mN complex possessed the highly efficient in vitro gene delivery ability to the hepatocellular carcinoma cells. The in vivo gene expression indicated that PP9mN could target to the tumor tissues effectively. By using the therapeutic AChE gene, it was found that the PP9mN complexes significantly enhanced the anti-tumor effect on tumor-bearing nude mice. Such monoclonal antibody-conjugated gene complex should have great potential applications in liver cancer therapy.     

Studies on polyamidoamine dendrimers as efficient gene delivery vector

Non-viral methods of gene delivery are attractive alternatives compared to virus-based gene delivery. Polyamidoamine (PAMAM) dendrimers are a new class of highly branched spherical polymers and have a unique surface of positively charged primary amine groups. They can form complex with DNA by electrostatic interaction, and deliver gene into cells. The ability of G5 PAMAM dendrimers binding and transferring DNA to cells has been investigated, and the effect of this complex to cell viability has been evaluated. G5 PAMAM dendrimers can bind DNA and transfer it to cultured cells efficiently, and have low cytotoxicity. The complex of PAMAM dendrimer-DNA can remain intact in a broad pH range, and also can prevent DNA from being degraded by restriction enzyme. Using the EGFP-C2 gene as marker genes, PAMAM dendrimers can deliver it to many organs after intravenous injection and have high expression in liver, kidney, lung, and spleen. Polyamidoamine- DNA complex can bind selectively plasma proteins, which may be correlated with its transportation in vivo. Polyamidoamine dendrimers' high-efficiency, low-cytotoxicity gene vector, appear to have potential for fundamental research and genetic therapy in vitro and in vivo.