【作者】 杨小超；

【导师】 莫志宏； Vincent M.Rotello；

【作者基本信息】 重庆大学 ， 生物医学工程， 2010， 博士

【摘要】 纳米金(AuNPs)具有独特的物理和化学性质,其物理性质主要表现为表面等离子体共振吸收、增强磁共振、表面增强拉曼散射以及荧光增强和淬灭;其化学性质主要包括抗氧化性、生物惰性、低细胞毒性以及容易通过Au–S共价结合含有巯基的配体。用含有巯基的功能性配体对AuNPs进行表面修饰,可以整合AuNPs的物理和化学性质以及修饰配体的特殊功能,赋予AuNPs全新的化学和生物功能,使其能够应用于生物转运、生物传感、生物成像和疾病治疗等研究领域。本文设计并合成了多种含有巯基的阳离子配体,通过配体交换法用这些阳离子配体对AuNPs进行表面修饰,制备了多种表面带有正电荷且具有特殊化学和生物功能的AuNPs,利用这些AuNPs的化学和生物功能,将其分别应用于细胞转运和微囊自组装研究。①阳离子多肽配体修饰的AuNPs用于基因转运研究。用多肽的固相合成法制备了四种阳离子短链多肽RRR、KKK、KRK和HKRK,将其连接到巯基化合物上后分别用于AuNPs的表面修饰,得到表面带有正电荷的RRR–AuNPs、KKK–AuNPs、KRK–AuNPs和HKRK–AuNPs,其中RRR–AuNPs在水溶液中分散性差,其它三种纳米粒子可以稳定的分散于水溶液中。将三种在水溶液中具有良好分散性的AuNPs作为基因转运载体,以β–半乳糖苷酶(β–gal)作为报告基因,293T细胞作为靶细胞进行基因转运研究。结果发现:三种AuNPs均能将质粒DNA转运至293T细胞内,并能使报告基因在细胞内成功表达,其基因转运效率依次为HKRK–AuNPs>KRK–AuNPs>KKK–AuNPs;细胞毒性分析实验结果显示,KKK–AuNPs具有微弱的细胞毒性,HKRK–AuNPs和KRK–AuNPs无明显细胞毒性;透射电镜(TEM)分析结果表明AuNPs转运载体进入细胞的通道为细胞内吞。②阳离子多肽配体修饰的AuNPs用于酶的细胞转运研究。HKRK–AuNPs在基因转运中表现出了细胞转染率高和细胞毒性低的特点,为深入研究HKRK–AuNPs的细胞转运功能,将其作为蛋白酶β–gal的转运载体,以HeLa、COS–1、C2C12和MCF7四种细胞作为靶细胞进行酶的细胞转运研究。结果发现:HKRK–AuNPs可通过静电吸附同β–gal结合,两者结合后β–gal的二级结构不会发生明显改变;HKRK–AuNPs可通过细胞内吞的方式将β–gal转运至细胞内,并且该纳米粒子具有将β–gal从细胞内吞过程中形成的内涵体中释放到细胞内的功能,被转运的β–gal在细胞内能保持其原有的生物活性;阿尔马蓝细胞活性分析法、台盼蓝排除法和钙黄绿素细胞活性分析法所得实验结果均显示,HKRK–AuNPs在实验条件下无细胞毒性,是一种优良的细胞转运载体。③阳离子季胺(TTMA)配体修饰的AuNPs辅助酶自组装催化微囊。将酶固定在比表面积大的球形载体上可提高酶的固定率和利用率,O/W乳滴是酶固定化的一种理想载体,但由于缺乏强烈的相互作用力,酶不能直接吸附在乳滴表面。用TTMA配体对AuNPs进行表面修饰,得到表面带有正电荷的TTMA–AuNPs,将其同带负电荷的β–gal通过静电吸附结合形成TTMA–AuNPs/β–gal复合物,用该复合物进行O/W乳滴界面的自组装研究。结果发现:单独的TTMA–AuNPs或β–gal不能在乳滴界面进行自组装,但TTMA–AuNPs/β–gal复合物却可以在乳滴界面自组装形成稳定的微囊;比较TTMA–AuNPs、β–gal和TTMA–AuNPs/β–gal复合物的表面电荷密度后发现,TTMA–AuNPs和β–gal的表面电荷密度远远高于TTMA–AuNPs/β–gal复合物,电荷密度降低是TTMA–AuNPs/β–gal复合物在乳滴界面发生自组装的主要驱动力;这种新型的自组装方法可将溶液中99%以上的β–gal固定到乳滴表面,并且β–gal固定到乳滴表面后其生物活性可保留76%。④阳离子精氨酸(Arg)配体修饰的AuNPs用于载药纳囊自组装研究。以纳米粒子作为囊壁的微囊在药物转运研究领域有潜在应用价值,但目前的方法只能自组装粒径在1~50μm左右的微囊,较大的尺寸限制了该类型微囊在细胞转运中的应用。纳米级微囊(纳囊)自组装困难的主要原因是纳米粒子难以克服纳米级乳滴的界面能和拉普拉斯压力差,针对该技术难点,本文设计了一种全新的纳囊自组装方法:首先用阳离子Arg配体对AuNPs进行修饰,得到表面带有正电荷的Arg–AuNPs,并用亚油酸作为油相制备纳米级O/W乳滴模板;然后将两者在溶液中混合进行自组装,Arg–AuNPs表面的精氨酸与亚油酸末端的羧基之间形成强烈的氢键相互作用,这种超分子作用使纳米粒子能够克服乳滴的界面能和拉普拉斯压力差,将纳米粒子组装到乳滴表面形成稳定的纳囊;最后用带负电荷的转铁蛋白对乳滴表面带正电荷的Arg–AuNPs进行交联,以进一步提高纳囊的稳定性。实验结果发现:Arg–AuNPs在亚油酸乳滴模板界面自组装释放出大量界面能,将纳米粒子牢固的吸附在乳滴表面;TEM和动态光散射(DLS)分析结果显示,这种基于超分子作用的方法可自组装粒径在~100 nm左右的纳囊;将自组装得到的纳囊用于抗癌药物紫杉醇在HeLa细胞中的转运研究,结果发现,在实验条件下纳囊自身无细胞毒性,但封装有紫杉醇的纳囊表现出强烈的细胞毒性,表明该纳囊是一种优良的药物转运载体。更多还原

【Abstract】 Gold nanoparticles (AuNPs) are versatile nanomaterials with unique physical and chemical properties. The typical physical properties of AuNPs include surface plasmon resonance, enhancement of magnetic resonance imaging, surface-enhanced Raman scattering, and enhancement and quenching of fluorescence. The chemical properties of AuNPs are represented by their oxidation resistance, bio–inertness, low cytotoxicity, and readily conjugate with thiolated compounds through Au–S bond. Moreover, the modification of AuNPs with functional thiolated ligands could combine the essential physical and chemical properties of the AuNPs and the chemical properties of the ligands, which impart the AuNPs new chemical and biological properties with applications as diverse as delivery, sensing, imaging and therapies. In this thesis, we designed and synthesized several thiolated cationic ligands. These functional ligands were used for AuNPs surface modification by using place–exchange strategy resulting in positively charged functional AuNPs, and the applications of the functionalized AuNPs for intracellular delivery and microcapsule self–assembly were studied.Cationic peptide ligand functionalized AuNPs as carrier for gene delivery. Cationic peptides RRR, KKK, KRK and HKRK were conjugated to thiol compound and used for AuNPs surface modification resulting in water insoluble RRR–AuNPs, and water soluble KKK–AuNP, KRK–AuNPs and HKRK–AuNPs. Based on the excellent water solubility, KKK–AuNP, KRK–AuNPs and HKRK–AuNPs were used as gene delivery carrier for the transfection of 293T cells withβ–gal reporter gene plasmid. The results showed that all of the three nanoparticles efficiently transfected 293T cells as determined byβ–gal activity. The transfection efficiency of the three nanoparticles were determined as HKRK–AuNPs>KRK–AuNPs>KKK–AuNPs. Maximum transfection was observed by using HKRK–AuNPs as carrier. The cell viability assay indicated that KKK–AuNPs were moderately toxic. However, full retention of cell vitality was observed for both KRK–AuNPs and HKRK–AuNPs. The TEM images revealed that the cell uptake mechanism for AuNPs was endocytosis.Cationic peptide ligand functionalized AuNPs as carrier for enzyme delivery. According to the gene delivery result, HKRK–AuNPs was a highly effective and low toxic carrier. To further explore the delivery properties of HKRK–AuNPs, the nanoparticle was used as enzyme carrier to transferβ–gal into HeLa, COS–1, C2C12 and MCF7 cells. The results indicated that theβ–gal conjugated to HKRK–AuNPs through electrostatic interaction forming HKRK–AuNPs/β–gal. Circular dichroism (CD) spectra revealed that HKRK–AuNPs had minimal effect on the secondary structure ofβ–gal. HKRK–AuNPs were able to transportβ–gal into all the four cell lines tested in the study. The temperature dependent experiment showed that the enzyme internalization via endocytosis. Most importantly, the transported enzymes were able to escape from endosomes and the enzymatic activity was kept after the delivery. Cell viability evaluated by alamar blue assay, trypan blue exclusion assay and calcein AM assay demonstrated no apparent cytotoxicity of the HKRK–AuNPs, which implied the nanoparticle an excellent carrier.Cationic quaternary ammonium (TTMA) ligand functionalized AuNPs for catalytic microcapsule self–assembly. The immobilization of enzymes on a template with high surface to volume ratio would increase the immobilization efficiency and the utility efficiency of the enzyme. For this purpose, O/W droplet provide and ideal geometry for enzyme immobilization. However, the lack of strong binding force between the droplet and enzyme limited the confinement of enzyme at the O/W droplet interface. To investigate the mimmobilization of enzymes on the O/W droplet surface, AuNPs were functionalized with cationic TTMA ligands resulting in positively charged TTMA–AuNPs. These cationic nanoparticles were conjugated toβ–gal forming TTMA–AuNPs/β–gal conjugates which were used for microcapsules self–assembly at O/W droplet interface. The results indicated that no self–assembly phenomenon was observed for both free TTMA–AuNPs and freeβ–gal. However, the TTMA–AuNPs/β–gal conjugates could be self–assembled onto the O/W droplet surface resulting in stable catalytic microcapsules. The surface charge density difference of the TTMA–AuNPs,β–gal and TTMA–AuNPs/β–gal conjugates revealed that the driven force for this self–assembly process is surface charge density decrease. Significantly, 99% of the freeβ–gal molecules were immobilized onto the O/W droplet surface and 76% of the enzymatic activity preservation was observed after the immobilization.Cationic arginine (Arg) ligand functionalized AuNPs for self–assembly of drug delivery nanocapsules. Nanoparticles stabilized microcapsules are of great potential in drug delivery applications. However, current methods can only generate microcapsules with size ranging from 1~50μm, limiting their effectiveness as delivery vehicles. The self–assembly of nano–sized microcapsules (nanocapsules) is still a chanllenge due to the presence of interfacial energy and Laplace pressure at the O/W droplets interface. To address this issue, AuNPs were functionalized with arginine liagnds, and linoleic acid was emulsified to generate nano–sized O/W droplet template. The strong hydrogen bonds between the arginine group on the Arg–AuNPs surface and carboxyl group at the terminal of the linoleic acid molecules guided the self–assembly of the nanoparticles at the O/W droplet interface forming stable nanocapsules. To further stabilize the nanocapsule, the positively charged Arg–AuNPs on the nanocapsule surface were crosslinked by negatively charged transferrin. The size of the nanocapsules was ~100 nm determined by TEM and DLS analysis. The application of the prepared nanocapsules for anti–cancer drug, paclitaxel, delivery was studied with HeLa cells. The nanocapsules showed no measurable toxicity, whereas efficient delivery and high cytotoxicity was observed with paclitaxel loaded nanocapsules. The prepared nanocapsule is supposed to be an excellent drug delivery vehicle.更多还原