壳聚糖纳米粒介导基因转染的影响因素及改性修饰

壳聚糖带正电荷,可与带负电荷的DNA结合形成纳米级的多聚复合物(纳米粒)。作为一种基因载体,壳聚糖对DNA具有很好的结合和保护作用,对生物体无毒、相容性好,被广泛应用于基因转染及基因预防和治疗中。壳聚糖的主要缺点是转染效率较低,但对其进行改性或修饰后,有可能提高其转染效率。     

两种阳离子纳米基因载体及植物基因介导效果的研究

以阳离子聚乙烯亚胺(polyethylenimine, PEI)和壳聚糖(chitosan, CS)作为两种植物基因载体,分别制备了载基因PEI纳米粒(PEI/DNA)和壳聚糖-DNA纳米粒(CS/DNA),并对其形态、粒度分布、包封率、DNA结合的稳定性及纳米颗粒对DNA的保护等方面进行表征.并以GFP基因为报告基因进行植物细胞转染,比较两者转化效率.结果表明PEI/DNA纳米粒稳定性,对DNA的保护以及转染效率等方面均优于壳聚糖-DNA纳米粒.     

TurboFect介导骨形态发生蛋白2 转染CHO 细胞的研究

目的:构建真核表达载体p IRES-EGFP-BMP-2,通过Turbo Fect转染得到表达BMP-2蛋白的CHO细胞系。方法:利用逆转录PCR方法扩增获得人的BMP-2基因c DNA,克隆入p MD18-T载体,经PCR、酶切和基因测序分析等方法鉴定重组质粒;将BMP-2连入p IRES-EGFP真核表达载体中,经限制性酶切和PCR扩增鉴定重组质粒。以壳聚糖和Turbo Fect分别作为基因载体转染CHO细胞,荧光显微镜检测分析转染结果;G418筛选富集转染阳性细胞。结果:成功的克隆得到了BMP-2基因,酶切鉴定成功构建了p IRES-EGFP-BMP-2质粒。与壳聚糖组相比,Turbo Fect用量为1:1时,细胞阳性率为(31.92±1.31)%,高于壳聚糖的细胞阳性率(6.33±1.53)%。目的基因与Turbo Fect比例为1:2时转染效率为(42.90±1.10)%高于1:1的(28.59±2.38)%和1:3的(37.52±2.14)%。细胞密度调节到5×103 cells/cm2阳性细胞率可达到(44.43±3.23)%。荧光检测可见荧光阳性细胞得到稳定传代。Western Blot检测可见BMP-2蛋白表达。结论:Turbo Fect成功的介导了p IRES-EGFP-BMP-2载体转染CHO细胞,建立了稳定表达BMP-2和EGFP的CHO细胞株。     

载基因壳聚糖纳米粒的制备及免疫增强作用的初步研究

摘 要 目的: 制备壳聚糖载基因纳米粒,并对其体外转染效率及其在小鼠体内的免疫增强效果进行初步研究。方法: 以本课题组构建的口蹄疫DNA疫苗为模型药物,采用复凝聚法制备纳米粒;用透射电镜观察形态;用纳米粒度分析仪测定粒径、多分散度和zeta电位;凝胶阻滞分析测定基因在纳米粒中的位置;用体外基因转染实验评价纳米粒的转染活性。用载基因壳聚糖纳米粒免疫雌性Balb/c小鼠,检测免疫小鼠的细胞免疫和体液免疫水平。结果: 所制备的载基因纳米粒形态规则、大多成球形,平均粒径约为150nm,多分散度＜0.26,zeta电位约为21mV;凝胶分析结果表明质粒DNA与壳聚糖分子间可以通过电性结合作用而完全结合,基因几乎全部被包裹在纳米粒内部;体外基因转染实验表明壳聚糖作为一种新型的非病毒基因递送载体能够高效传递DNA进入BHK-21细胞,基因能够在该细胞中高效表达;小鼠免疫实验表明纳米粒不仅能诱导机体产生较高的细胞免疫水平,而且体液免疫水平也显著提高。结论: 壳聚糖纳米粒能将基因递送到细胞内并且能够表达,小鼠免疫实验显示其具有良好的免疫增强效果。     

基因治疗微链载体的构建及表达分析

基因载体的转染、表达效率低和存在安全问题是基因治疗的难点。由于传统病毒及质粒载体含有大量外源基因, 其表达有可能引发较严重免疫副反应。本课题旨在新的设计思路上开发高效安全基因治疗载体。 微链载体利用设计好的Cap序列封闭基因表达框两端, 起到防止细胞内核酸外切酶降解的作用。从pEGFP-N3质粒中分离纯化得到GFP基因作为微链载体的报告基因。将微链载体与原质粒载体(pEGFP-N3质粒)分别转染入真核细胞, 利用荧光显微镜和流式细胞仪检测并比较其转染效率。结果显示微链载体在293、CNE2、3T3、B95-8等真核细胞中的转染、表达效率较高, 并具有较小的细胞毒性。初步证实了微链载体在真核细胞中转染、表达效率及安全性等方面具有一定的优越性。     

阳离子脂质体的转染机制及转染效率影响因素

阳离子脂质体是一种非常具有发展前景的基因载体。简要介绍了阳离子脂质体的结构特点;着重讨论了阳离子脂质体作为基因载体时介导基因转移的机制以及在转染过程中对基因转染效率产生影响的主要因素。     

外源基因转染山羊体细胞的整合效率研究

为了探讨影响山羊体细胞中外源基因整合效率的因素,采集胎羊和小羊皮肤并制备成纤维细胞,采用"Lipofectamine LTX"脂质体转染试剂包埋外源基因,分别导入上述细胞中,比较同一种外源基因载体(人凝血因子Ⅸ)转染至不同个体和类型的羊细胞,以及不同载体(人凝血因子Ⅸ、人转铁蛋白和牛催乳素)转染至同一个体羊细胞的整合效率的差异.通过药物筛选得到单细胞簇,经定量PCR计算外源基因的整合效率.同一种外源目的基因载体转染小羊成纤维细胞的整合效率显著高于胎羊成纤维细胞(P<0.05);而不同目的基因载体转染同一个体羊细胞,其细胞的整合效率与转染载体的片段大小有关.由此可知,小羊成纤维细胞外源基因整合频率优于胎羊细胞,且载体片段的大小影响外源基因转染的整合频率.     

阳离子脂质体的转染机制及转染效率影响因素

阳离子脂质体是一种非常具有发展前景的基因载体。简要介绍了阳离子脂质体的结构特点;着重讨论了阳离子脂质体作为基因载体时介导基因转移的机制以及在转染过程中对基因转染效率产生影响的主要因素。     

新型纳米转染试剂转染PNP自杀基因体外杀伤实验

将壳聚糖纳米粒包裹的报告基因pEGFP-N1质粒转染至HEK293细胞,并在HEK293细胞中成功表达荧光蛋白的基础上,进一步将本室自行构建的PNP基因的真核高效表达载体质粒pcDNA3-PNP转染至HEK293细胞。转染72h后,对转染的HEK293细胞给予前体药6-MPDR至终浓度40μg/ml,一天后,采用MTT比色法测定药物对细胞增值的影响,并进行统计学处理。实验结果表明采用壳聚糖纳米粒转染试剂转染并给予前体药6-MPDR的实验组活细胞数,与用壳聚糖转染但不给前体药6-MPDR的对照组活细胞数相比,有显著差异(P<0.05),说明新筛选出的壳聚糖纳米粒转染试剂可以将PNP自杀基因递送至靶细胞中,并在细胞中进行表达,从而使PNP/6-MPDR自杀基因系统发挥杀伤细胞的作用。分别采用相同工作浓度的脂质体与壳聚糖纳米粒转染试剂转染相同浓度的基因质粒,壳聚糖纳米粒对靶细胞生长数量影响很小,说明的壳聚糖纳米粒细胞毒性大大低于阳离子脂质体的细胞毒性。     

可磷酸化短肽偶联壳聚糖促进CS/DNA转染效率

合成基序为LLLRRRDNEY*FY*VRRLL的短肽(pSP),其中含有两个可被JaK2蛋白激酶磷酸化的酪氨酸残基.将此短肽与壳聚糖(CS)相偶联,体外磷酸化及DNA释放实验检测哺乳动物细胞裂解液对短肽的磷酸化及pSP-CS/DNA复合物中DNA释放的影响.放射性标记DNA转移实验验证pSP-CS/DNA复合物的入胞能力后,将荷荧光素酶或GFP报告基因的质粒与pSP-CS制成pSP-CS/DNA复合物,转染体外培养的C2C12小鼠成肌细胞,观察GFP的分布及细胞裂解液中的荧光素酶活性以表征转染效率.继而进行多种细胞系的转染,衡量pSP偶联的壳聚糖对不同种属细胞的转染效率.结果表明,哺乳动物细胞裂解液可有效地使短肽发生磷酸化,并藉此促进DNA与壳聚糖载体的解离.以pSP修饰的壳聚糖进行转染时,细胞裂解液的荧光素酶活性可达普通壳聚糖转染的两倍,细胞中GFP的含量也明显增加.据此推论,短肽被磷酸化后产生电荷属性的改变,促进DNA与壳聚糖载体的解离从而显著提高壳聚糖的转染效率.     

Dendronized chitosan derivative as a biocompatible gene delivery carrier

To improve the transfection efficiency of chitosan as a nonviral gene delivery vector, a dendronized chitosan derivative was prepared by a copper-catalyzed azide alkyne cyclization reaction of propargyl focal point poly(amidoamine) dendron with 6-azido-6-deoxy-chitosan. Its structure was characterized by (1)H NMR and FTIR analyses and its buffering capacity was evaluated by acid-base titration. In particular, its complexation with plasmid DNA was investigated by agarose gel electrophoresis, zeta potential, and particle size analyses as well as transmission electron microscopy observation. Compared to unmodified chitosan, such a chitosan derivative has better water solubility and buffering capacity. Compared to commonly used polyethyleneimine (PEI, 25 kDa), it could exhibit enhanced transfection efficiency in some cases and lower cell toxicity, as confirmed by in vitro transfection and cytotoxicity tests in human kidney 293T and human nasopharyngeal carcinoma CNE2 cell lines. In addition, the effect of serum on its transfection efficiency was also studied.     

Methylated N-(4-N,N-dimethylaminobenzyl) chitosan as effective gene carriers: Effect of degree of substitution

The objective of this study was to investigate the transfection efficiency of quaternized N-(4-N,N-dimethylaminobenzyl) chitosan; TM-Bz-CS, using the plasmid DNA encoding green fluorescent protein (pEGFP-C2) on human hepatoma cell lines (Huh7 cells). The factors affecting the transfection efficiency e.g. degree of quaternization (DQ), the degree of dimethylaminobenzyl substitution (DS) and polymer/DNA weight ratio, have been evaluated. The results revealed that all TM-Bz-CS derivatives were able to condense with DNA. Illustrated by agarose gel electrophoresis, complete complexes of TM₅₇-Bz₄₂-CS/DNA were formed at weight ratio of above 0.5, whereas those of TM₄₇-Bz₄₂-CS/DNA and TM₅₇- Bz₁₇-CS/DNA were above 1. The rank of transfection efficiency of the chitosan derivatives were TM₅₇-Bz₄₂-CS > TM₄₇-Bz₄₂-CS > TM₅₇-Bz₁₈-CS. The pH of culture medium did not affect the transfection efficiency of TM₅₇-Bz₄₂-CS/DNA complex, whereas it affected the transfection efficiency of chitosan/DNA complex. The results indicated that the improved gene transfection was due to the hydrophobic group (N,N-dimethylaminobenzyl) substitution on chitosan which promoted the interaction and condensation with DNA as well as N-quaternization which increased chitosan water solubility and enhance gene expression. For cytotoxicity studies, TM-Bz-CS was safe at the concentration of the highest transfection. In conclusion, this novel chitosan derivative, TM₅₇-Bz₄₂-CS showed elevated potential as gene carrier by efficient DNA condensation and mediated highest level of gene transfection with negligible cytotoxicity in Huh7 cells.     

Exploring N-imidazolyl-O-carboxymethyl chitosan for high performance gene delivery

Chitosan shows good biocompatibility and biodegradability, but the poor water solubility and low transfection efficiency hinder its applications as a gene delivery vector. We here report the detailed synthesis and characterization of a novel ampholytical chitosan derivative, N-imidazolyl-O-carboxymethyl chitosan (IOCMCS), used for high performance gene delivery. After chemical modification, the solubility of the resulting polymer is enhanced, and the polymer is soluble in a wide pH range (4-10). Gel electrophoresis study reveals the strong binding ability between plasmid DNA and the IOCMCS. Moreover, the IOCMCS does not induce remarkable cytotoxicity against human embryonic kidney (HEK293T) cells. The cell transfection results with HEK293T cells using the IOCMCS as gene delivery vector demonstrate the high transfection efficiency, which is dependent on the degree of imidazolyl substitution. Therefore, the IOCMCS is a promising candidate as the DNA delivery vector in gene therapy due to its high solubility, high gene binding capability, low cytotoxicity, and high gene transfection efficiency.     

Lactosylated chitosan for DNA delivery into hepatocytes: the effect of lactosylation on the physicochemical properties and intracellular trafficking of pDNA/chitosan complexes

Chitosan is a useful nonviral vector for gene delivery. To make a pDNA/chitosan complex specific to hepatocytes, lactose-modified chitosan (lac-chitosan) was synthesized. When the percentage of lactose residues substituted was 8%, lac-chitosan showed excellent DNA-binding ability, good protection of DNA from nuclease, and the suppression of self-aggregation and serum-induced aggregation. Although the cellular uptake efficiency of the pDNA/lac-chitosan complex was almost the same as that of the pDNA/chitosan complex, the cell transfection efficiency of the former was greater for HepG2 cells having asialoglycoprotein receptors. Inhibitor of endocytosis such as bafilomycin A1 and nocodazole significantly reduced the transfection efficiency of the pDNA/lac-chitosan complex. Observations with a confocal laser scanning microscope indicated that the pDNA/lac-chitosan complexes traversed endocytic compartments more rapidly than the pDNA/chitosan complex. Furthermore, the pDNA/lac-chitosan complexes were delivered to the late endosome and have the advantage of delivering DNA to the perinuclear region.     

PAMAM conjugated chitosan through naphthalimide moiety for enhanced gene transfection efficiency

Development of efficient and safe gene carrier is the main hurdle for successful gene therapy till date. Poor water solubility and low transfection efficiency of chitosan are the main drawbacks to be efficient gene carrier for successful gene therapy. In this work, PAMAM conjugated chitosan was prepared through naphthalimide moiety by simple substitution reaction. The synthesis of the chitosan conjugates was confirmed by FTIR, ¹H NMR and XRD analyses. The conjugates showed enhanced DNA binding capability compared to that of unmodified chitosan. Moreover, the conjugates showed minimal cytotoxicity compared to that of polyethyleneimine (PEI, 25 kDa) and also showed good blood compatibility with negligible haemolysis. The transfection efficiency of the conjugate was significantly increased compared to that of unmodified chitosan and it also surpassed the transfection efficiency by PEI. Therefore, PAMAM conjugated chitosan can be used safely as alternate efficient gene delivery vector in gene therapy.     

Sustained expression in mammalian cells with DNA complexed with chitosan nanoparticles

This work investigates the preparation and in vitro efficiency of chitosan gene transfection systems. Chitosan was used to prepare nanoparticles with a size range of 40-200 nm as determined using photon correlation spectroscopy (PCS) and 40-80 nm as determined using transmission electron microscopy (TEM). The ability of particles to complex DNA was investigated using gel retardation. Plasmid DNA pGL3-Control encoding firefly luciferase and pCH110 encoding beta-galactosidase were used as reporter genes. For transfection 293 human embryonal kidney cells and Chinese hamster ovary (CHO-K1) cells were used. The expression of luciferase was assayed and expressed as relative light units per milligram of protein (RLU/mg protein). Results showed that these chitosan particles have potential as vectors for the transfer of DNA into mammalian cells. Cellular transfection by the chitosan-pGL3-Control particles showed a sustained expression of the luciferase gene for about 10 days. Commercial transfection reagents, SuperFect and Lipofectin were also used. In contrast to chitosan particles, the duration of expression for both SuperFect and Lipofectin was only about 2 days. Agarose gel electrophoresis and displacement experiments using polyaspartic acid indicated a probable multiple interaction between DNA and chitosan whilst the interaction between DNA and the polyamidoamine dendrimer appears to be only ionic interaction. No toxic effect on the mammalian cells was seen with chitosan. SuperFect and Lipofectin however, were observed to engender marked cytotoxicity. Poly-D,L-lactide (PLA) nanoparticles (40-80 nm) and poly-L-lactide (PLLA) lamellae (2-6 microm) were also used to load DNA by an adsorption procedure, but these failed to give good expression data.     

Human-derived NLS enhance the gene transfer efficiency of chitosan

Nuclear import is considered as one of the major limitations for non-viral gene delivery systems and the incorporation of nuclear localization signals (NLS) that mediate nuclear intake can be used as a strategy to enhance internalization of exogenous DNA.In this work, human-derived endogenous NLS peptides based on insulin growth factor binding proteins (IGFBP), namely IGFBP-3 and IGFBP-5, were tested for their ability to improve nuclear translocation of genetic material by non-viral vectors. Several strategies were tested to determine their effect on chitosan mediated transfection efficiency: co-administration with polyplexes, co-complexation at the time of polyplex formation, and covalent ligation to chitosan. Our results show that co-complexation and covalent ligation of the NLS peptide derived from IGFBP-3 to chitosan polyplexes yields a 2-fold increase in transfection efficiency, which was not observed for NLS peptide derived from IGFBP-5.These results indicate that the integration of IGFBP-NLS-3 peptides into polyplexes has potential as a strategy to enhance the efficiency of non-viral vectors.     

钠米颗粒介导质粒DNA转染体外真核细胞

DNA传递是基因表达与功能研究及其医学应用的重要技术,安全高效的DNA传递一直是研究者期待的目标。利用一种新的阳离子多聚物脱乙酰甲壳胺16介导重组质粒pcDNA3vp1转染COS7细胞,RTPCR可检测到目的基因vp1在mRNA水平的表达,实时定量PCR结果表明其转染效率介于脂质体与磷酸钙法之间,同时还对转染条件进行了探讨。DNA结合分析发现脱乙酰甲壳胺16能够与DNA形成核酸纳米颗粒,提高DNA稳定性,促进真核细胞转染效率的提高。这些结果表明脱乙酰甲壳胺16确能做为一种新型的非病毒纳米DNA传递载体,并将可能在基因表达与功能研究及基因治疗等领域发挥重要作用 。     

Preparation, characterization and transfection efficacy of chitosan nanoparticles containing the intestinal trefoil factor gene

Intestinal trefoil factor (ITF) is a novel polypeptide with potential pharmacological value for the prevention and healing of tissue injury; however, poor production capacity limits its clinical application. Chitosan, as a non-viral vehicle, has been successfully used in gene delivery for its intrinsic characteristics. In this context, we prepared chitosan nanoparticles enwrapping ITF cDNA and investigated its size, zeta potential, stability, release profiles, loading efficiency and loading capacity. Gene transfer capability was assessed in HEK293 cells. The data revealed that the chitosan/DNA nanoparticles were successfully prepared with sizes less than 500 nm and positive zeta potentials. The nanoparticles could protect DNA from nuclease degradation, and release profiles of DNA were dependent on N/P ratios. In addition, transfection efficiency of chitosan/DNA nanoparticles was equivalent to Lipofectamine (TM). Collectively, the results suggest that chitosan/DNA nanoparticles could be a promising method for ITF gene therapy.