胆固醇修饰的低分子量聚乙烯亚胺接枝化聚[L-天冬酰胺-co-L-赖氨酸]作为基因载体的性能研究

通过将低分子量的聚乙烯亚胺(PEI600)及其胆固醇衍生物与聚(L-天冬酰胺-co-L-赖氨酸)(PSL)进行开环反应, 合成了一类新型的肿瘤靶向基因载体, 研究了这类载体与DNA形成复合物的性质以及介导绿色荧光蛋白质粒pEGFP-C1转染不同细胞的性能. 结果表明, 在复合质量比大于5∶1时, 各载体均能与DNA形成结构稳定的复合物. 同时转染实验结果证明, 通过在侧链引入一定数目的胆固醇, 可以明显提高载体对于癌细胞HepG2和Hela的转染效率. 这类新型的载体具有良好的细胞相容性、较高的转染效率以及易于进行靶向修饰等特点, 在基因治疗研究领域中将具有较好的潜在应用价值.     

PEI基因载体靶向遮蔽体系的制备和表征

将RGD短肽接枝到聚谷氨酸(PGA)上,制备了一种靶向性的基因载体遮蔽材料PGA-RGD.通过凝胶电泳实验及体外转染实验证明得出RGD的引入增加了载体材料与细胞表面受体的特异性作用,在载体表面正电荷得到遮蔽的同时,转染效率还得到了一定程度的增加.同时,对转染了48h的三元复合物进行MTT细胞毒性测试表明,PGA遮蔽的基因载体体系(PGA/PEI/DNA)和PGA-RGD遮蔽的基因载体体系(PGA-RGD/PEI/DNA)的细胞毒性均低于PEI/DNA复合物体系.本文开发的基因载体改性方法不仅可以对复合物颗粒表面的正电荷进行遮蔽,从而降低复合物体系对非目标组织的非特性异作用;同时引入的RGD靶向短肽还可以提高载体的靶向性,这一改性策略对推动阳离子聚合物基因载体在体内的应用具有重要意义.     

主客体组装构建环糊精修饰基因微载体的研究

合成了二茂铁接枝聚乙烯亚胺( PEI-Fc),利用二茂铁与β-环糊精的主客体嵌套作用制备了环糊精修饰聚乙烯亚胺,核磁测定结果显示,每条PEI-Fc链上通过主客体作用嵌套的CD平均为26个.这种基于弱相互作用力的β-环糊精修饰聚乙烯亚胺能有效诱导DNA分子的缔合,在N/P值达到3以上时,可形成表面为正电荷、粒径为150 ～ 250 nm的球形粒子.在含10％胎牛血清的DMEM体外细胞培养基中,由于培养基中的蛋白质能够在粒子表面发生静电吸附,PEI-Fc/CD/DNA基因微载体显示出良好的稳定性.HEK293细胞培养结果显示,以表达绿色荧光蛋白的质粒pEGFP为模型,以N/P值为10的PEI/DNA组装体作为对照,N/P值为3、5和10的PEI-Fc/CD/DNA组装体的转染效率均达到对照组的2～3倍,这种基于主客体组装构建的环糊精修饰基因微载体显著提高了基因转染效率.     

靶向性载体/基因复合物促进内皮细胞增殖

由于人工血管的表面缺乏活性内皮层,特别是小口径人工血管经常面临着长期通畅率低和再狭窄等难题,从而限制了其在临床上的应用。研究表明,通过基因复合物对内皮细胞转染可以在支架表面快速获得新生内皮层。近年来,基于靶向多肽修饰的基因载体为提高转染效率和降低载体毒性提供了有效的途径。本文详细介绍了目前用于基因转染的各种目的基因和基因载体,并以聚阳离子基因载体为基础,重点阐述了促进内皮细胞增殖的靶向性基因载体的研究进展,结合当前小口径人工血管研究进展,对采用基因转染方式实现其快速内皮化进行了分析和展望。     

聚苯丙氨酸修饰低分子量聚乙烯亚胺制备高效基因载体

分别制备了以支化小分子量聚乙烯亚胺(PEI-1.8k)为引发剂,引发苯丙氨酸-NCA开环聚合得到聚乙烯亚胺-聚苯丙氨酸(PEI1.8k-g-PPhe)以及聚乙烯亚胺接枝苯丙氨酸单体(PEI1.8k-g-Phe)的系列基因载体材料.利用核磁、粒度、zeta电位仪、荧光光度计、流式细胞仪以及激光共聚焦显微镜对PEI1.8k-g-PPhe,PEI1.8k-g-Phe以及PEI1.8k-g-PPhe/DNA和PEI1.8k-g-Phe/DNA复合物颗粒进行了系统的表征.研究结果表明,最佳转染条件下,PEI1.8k-g-PPhe10/DNA复合物颗粒的粒径约为150 nm,表面电位约为16 m V.在人源宫颈癌(He La)和人源乳腺癌(MCF-7)2种细胞系中均具有较高的基因转染效率,且最佳转染效率可达到PEI-25k的12倍.MTT细胞毒性实验分别比较了PEI1.8k-g-PPhe和PEI1.8k-g-Phe对He La细胞毒性的大小.从实验结果可见,苯丙氨酸引入的方式及数量决定着其细胞毒性的大小.PEI1.8k-g-PPhe和PEI1.8k-g-Phe都具有较低的细胞毒性(材料在较高浓度1 mg/m L时的细胞存活率大于70%).内吞实验结果表明,PEI1.8k-g-PPhe由于接入了具有规则聚合链的聚苯丙氨酸,而易于被He La细胞内吞.PEI1.8k-g-PPhe10/DNA复合物颗粒相比于PEI-25k/DNA,PEI-1.8k/DNA和PEI1.8k-g-PPhe/DNA具有更高的细胞内吞效率.     

末端功能化的树枝状聚合物载体与质粒组装的热力学和动力学

通过二代和四代聚酰胺-胺树枝状聚合物(G2和G4表示)末端分别修饰苯丙氨酸和色氨酸合成了多种新型聚合物载体,进而考察了其与质粒的组装行为.研究结果显示,Phe-G4和Trp-G4与质粒组装为结构致密的纳米粒子,其中Phe-G4与质粒形成的纳米粒子更加紧密.这一过程是由聚合物载体与质粒间的静电相互作用和结构重排共同驱动的.此外,末端修饰方法显著降低了载体的细胞毒性.细胞转染结果表明,Phe-G4和Trp-G4成功介导质粒pEGFP-CL在COS-7细胞中表达,Phe-G4/pEGFP-CL的转染效率提高到作为阳性对照的脂质体组的4倍以上.因此,Phe-G4载体是一种有应用潜力的新型基因传递系统.     

细胞核靶向聚乙烯亚胺-地塞米松偶联物的制备及作为基因载体的应用

采用地塞米松(Dex)和低分子量聚乙烯亚胺(PEI)经酰胺化反应, 合成了一种新型靶向基因载体PEI-Dex偶联物. 研究结果表明, PEI-Dex可结合DNA形成复合物, 在最佳制备条件下(N/P=12), PEI-Dex/DNA复合物粒径为(162±1.90) nm, 电位为(12.8±0.11) mV, 适用于基因转染. PEI-Dex的细胞毒性较低, 可促进复合物的细胞核转运, 从而显著提高转染效率.     

交联型聚乙烯亚胺智能基因载体的制备及PEG化影响

使用胱胺双丙烯酰胺(CBA)对低分子量聚乙烯亚胺(PEI)进行交联反应制备智能降解型聚阳离子基因载体.通过与聚乙二醇(PEG)反应得到不同程度PEG化的聚阳离子载体.利用核磁、黏度测试、粒度仪、zeta电位仪和凝胶电泳对聚阳离子载体及其与DNA的复合物进行了表征.研究表明随着PEG含量的增加,聚阳离子载体/DNA复合物颗粒粒径变小、表面正电荷降低,PEG具有明显的屏蔽作用,但过多的PEG也使载体与DNA复合能力下降.通过MTT细胞毒性测试和荧光素酶质粒转染实验得出,含二硫键的交联型阳离子聚合物在测试范围内显示了非常低的细胞毒性,最佳转染效率是PEI25k的4倍,PEG化后其细胞毒性得到进一步改善,转染效率却明显降低.     

聚酰胺-胺型树枝状大分子及其衍生物在基因传递中的应用

基因治疗通过基因载体将治病基因导入病患的特异细胞以治疗心血管、神经系统疾病和癌症等。寻找安全高效的非病毒基因载体一直是基因治疗以及生物材料领域中的前沿课题。聚酰胺-胺型(PAMAM)树枝状高分子作为一类三维的、结构高度有序的新型载体,由于具有安全性好、易于修饰、携带外源基因容量大等特点,已经引起了广泛的关注。但是另一方面,合成步骤相对繁琐、后期产物纯化困难以及转染效率相对较低等问题限制了这类载体的进一步发展。本文结合本课题组的研究情况,针对如何提高PAMAM的转染效率以及增强其基因传递的靶向性等相关问题,对近几年在PAMAM树枝状分子修饰改性方面所做的一些有意义的工作进行了综述,并对前景进行了展望。     

阳离子基因载体的pH敏感遮蔽体系的制备及表征

合成了一种pH敏感的遮蔽体系-谷氨酸苄酯/谷氨酸共聚物(PBLG-co-PGA), 用于对DNA/阳离子基因载体复合物颗粒表面正电荷的遮蔽, 以提高其在体内的稳定性. 研究表明, PBLG-co-PGA (PGA(x), x为PGA占共聚物中摩尔百分数)具有pH敏感性. 并以pH敏感点接近生理pH值的PGA(60)为遮蔽体系进行研究. PGA(60)能够对DNA/PEI(1:1)复合物颗粒表面正电荷进行有效遮蔽. 凝胶阻滞电泳显示, 用PGA(60)对DNA/PEI复合物进行不同比例遮蔽, 没有发生与DNA的链交换作用. MTT细胞毒性测试表明, PGA(60)和三元复合物DNA/PEI/PGA(60) 在测试范围内几乎没有细胞毒性. 荧光素酶转染实验表明, 部分遮蔽后转染效率有所提高; 用PGA(60)对DNA/PEI复合物完全遮蔽为负电后, 由于同细胞表面的电荷排斥作用, 三元复合物不易被细胞内吞, 导致不发生细胞转染. 因其合适的pH响应性, PGA(60)将可能成为一种能随pH值的变化, 实现对聚阳离子基因载体进行电荷遮蔽/智能释放的遮蔽材料.     

MicroRNA Delivery with Bioreducible Polyethylenimine as a Non‐Viral Vector for Breast Cancer Gene Therapy

Polyethylenimines (PEIs) are outstanding macromolecules belonging to the polycations used in gene transfection. The transfection efficiency and cytotoxicity of PEIs increase with the increase in their molecular weight. To break up the correlation between transfection efficiency and cytotoxicity for non‐viral gene delivery, disulfide cross‐linked polyethylenimine (PEI‐SS) has been widely employed as highly efficient gene vectors for DNA/siRNA delivery in numerous efforts. In this work, PEI‐SS is described as a non‐viral vector for miRNA delivery for the first time. PEI‐SS is synthesized via cross‐linking using disulfide bonds as the cross‐linker from low molecular weight PEI. PEI‐SS can efficiently bind anti‐miR‐155 to form the polyplex with nano‐sized spherical structures in the size range of 10–100 nm. The polyplex is degraded by glutathione (GSH, a reducing agent) in cancer cells. Anti‐miR‐155 is then released to efficiently inhibit tumor growth.     

(Coixan polysaccharide)-graft-polyethylenimine folate for tumor-targeted gene delivery

CP-PEI-FA was prepared as an effective vector for in vitro and in vivo tumor-targeted gene delivery. The structures of the polymers were characterized, and their DNA condensation capability, particle sizes, zeta potentials, cytotoxicity and in vitro/in vivo transfection were examined. The cytotoxicity of CP-PEI-FA was significantly lower than that of PEI 25 kDa and close to that of PEI 1200. The in vitro transfection of CP-PEI-FA was tested in C6 and HeLa cells (FR-positive cells) and A549 cells (FR-negative cells). CP-PEI-FA showed a high targeting specificity and good gene transfection efficiency in FR-positive cells. These results indicate that CP-PEI-FA is a safe and effective polyplex-forming agent for both in vitro and in vivo transfection of plasmid DNA.     

High-molecular-weight polyethyleneimine conjuncted pluronic for gene transfer agents

In order to enhance the gene delivery efficiency and decrease cytotoxicity of polyplexes, copolymers consisting of branched polyethyleneimine (PEI) 25 kDa grafted with Pluronic (F127, F68, P105) were successfully synthesized using a simple two-step procedure. The copolymers were tested for cytotoxicity and DNA condensation and complexation properties. Their polyplexes with plasmid DNA were characterized in terms of DNA size and surface charge and transfection efficiency. The complex sizes were below 300 nm, which implicated their potential for intracellular delivery. The Pluronic-g-PEI exhibited better condensation and complexation properties than PEI 25 kDa. The cytotoxicity of PEI was strongly reduced after copolymerization. The Pluronic-g-PEI showed lower cytotoxicity in three different cell lines (Hela, MCF-7, and HepG2) than PEI 25 kDa. pGL3-lus was used as a reporter gene, and the transfection efficiency was in vitro measured in HeLa cells. Compared with unmodified PEI 25 kDa Pluronic-g-PEI showed much higher transfection efficiency. These results demonstrate that polyplexes prepared using a combined strategy of surface crosslinking and grafted with Pluronic seem to provide promising properties as stable, high transfection efficiency vectors.     

Bimodal Targeting Using Sulfonated,Mannosylated PEI for Combined Gene Delivery and Photodynamic Therapy

Photodynamic therapy (PDT) and gene delivery have both been used to target both cancer cells and tumor‐associated macrophages (TAMs). Given the complex nature of tumor tissue, there could be merit in combining these strategies simultaneously. In this study, we developed a bimodal targeting approach to both cancer cells and macrophages, employing materials conducive to both gene delivery and PDT. Polymers libraries were created that consisted of cationic polyethyleneimine (PEI) conjugated to the photosensitizer pyropheophorbide‐a, with sulfonation (to target selectin‐expressing cells) and mannosylation (to target TAMs). Polyplexes, consisting of these polymers electrostatically bound to DNA, were analyzed for transfection efficacy and cytotoxicity toward epithelial cells and macrophages to assess dual‐targeting. This study provides preliminary proof of principle for using modified PEI for targeted gene delivery and PDT.     

Hydrogen bonds in polycation improve the gene delivery efficiency in the serum-containing environment

Cationic polymers with high charge density could effectively condense the DNA and achieve gene transfection; however, it often brings non-negligible cytotoxicity. Notably, the high charge density gene vector fails in the serum environment, limiting further application in vivo. In this paper, an efficient and reliable non-viral gene vector of poly (amidoamine) (PAA) was designed by introducing diacryolyl-2,6-diaminopyridine (DADAP) onto the PAA backbone through Michael-addition polymerization, which provides high transfection efficiency in a serum-containing environment. Diacryolyl-2,6-diaminopyridine and cationic parts provided multiple interactions between gene vectors and DNA, including hydrogen bond and electrostatic interactions. The introduction of hydrogen bonding can effectively reduce the charge density of polyplexes without reducing the DNA condensing ability, incorporating the diaminopyridine group and cationic part in PAA chains successfully consolidated cellular uptake, endosome destabilization, and transfection efficiency for the PAA/DNA complexes with low cytotoxicity. The constructed vector with multiple interactions presented 6 times higher transfection efficiency in serum-free and 9 times in serum-containing environment than that of branched polyethyleneimine (PEI 25K) in 293T cells in vitro. Therefore, introducing the hydrogen band to form low charge density polyplexes with high transfection efficiency and low cytotoxicity has a great potential in gene delivery.     

A facile approach to construct hyaluronic acid shielding polyplexes with improved stability and reduced cytotoxicity

A facile approach for polymer gene carriers was used to construct hyaluronic acid (HA) shielding polyplexes due to the electrostatic interaction. By adding HA to PEI/DNA complexes, the ξ-potential of ternary polyplexes was changed from positive to negative. Spherical particles with diameter about 250nm were observed. Ethidium bromide exclusion assay indicated that the electrostatic complexation was loosened after addition of HA. However, DNA disassembly did not occur. The proper reason was that the intensity of negative charges was not strong enough to release DNA from the complexes in our experiment. The stability of PEI/DNA/HA polyplexes in physiological condition was improved and the cytotoxicity was reduced. Comparing with PEI/DNA polyplexes, the uptake and transfection efficiency of HA shielding polyplexes was lower for HEK293T cells probably due to the reduced adsorptive endocytosis, whereas it was higher for HepG2 cells due to HA receptor mediated endocytosis. This facile approach to constructing HA shielding polyplexes might have great potential application in non-viral gene delivery research and tumor therapy.     

基于门舒特金反应的酶触发自降解高分子载体及其在基因输送中的应用

用邻位苄基溴与双胺进行门舒特金反应,合成了2种线性的季铵盐阳离子聚合物.其中,含有酚基酯键的阳离子聚合物,一旦进入细胞后,可以在细胞内的酯酶催化下快速水解,使得聚合物自降解断裂为不带电的非季铵盐小分子,从而快速释放DNA,最终达到提高转染效率的目的.通过对复合物纳米颗粒的粒径和电势测定,证明了这2种阳离子聚合物都能够有效地结合DNA形成表面带正电的复合物纳米颗粒.凝胶阻滞电泳实验表明,所合成的阳离子聚合物都能稳定地包裹DNA.而在酯酶条件下,含有酚基酯键的阳离子聚合物可以发生降解,使得纳米复合物释放出DNA.同时,含有酚基酯键的阳离子聚合物由于其独特的可降解性,相比于PEI,降低了细胞毒性.在体外细胞转染实验中,2种阳离子聚合物都有较好的转染效果.其中酯酶响应的载体在高N/P下依然表现出较高的转染效率,说明该阳离子载体能够在细胞内有效降解并释放出DNA.