Efficient Sequestration of Congo Red Dye from Aqueous Solutions Using Pamam Dendrimer-Silica Composite

This study investigates the removal of Congo Red dye from aqueous solution using functionalized generation 3.0 and 5.0 polyamidoamine dendrimer-silica gel composite (G-3PS, G-5PS). Fourier Transform-Infra Red spectroscopy, Brunauer Emmett and Teller, Thermo Gravimetric Analysis, pH at point of zero charge, and scanning electron microscopy measurements have been applied to characterize the synthetic nanohybrid composite, these techniques revealed the successful functionalization of both dendrimer molecules and subsequent immobilization onto silica gel. The implications of varying adsorption parameters such as contact time, initial concentration of adsorbate, temperature and pH on both composites were studied. Experimental data obtained from batch adsorption processes were fitted into two equilibrium isotherms (Langmuir and Freundlich) and 3 kinetic models (Pseudo-First-Order, Pseudo-Second-Order, Intra Particle Diffusion). Adsorption mechanism was mainly governed by film diffusion due to electrostatic interactions between the functionalized dendrimer surface and Congo Red molecules. Thermodynamic parameters illustrate that the adsorption is endothermic and spontaneous. Findings suggest the Nanocomposites (G-3PS and G-5PS) are good adsorbents for the removal of Congo Red dye from aqueous solutions.

Pyridine terminated polyurethane dendrimer/chlorinated butyl rubber nanocomposites with excellent mechanical and damping properties

Due to the special viscoelastic property, traditional rubber with high performance has been widely used in human life and production. However, it is challenging to improve the damping property without sacrificing the extensibility. In this work, a novel type of second-generation polyurethane dendrimer terminated with pyridine(G2-Py) was synthesized by using thiolactone chemistry and subsequently complexed with Zn ions. The structure and morphology of G2-Py were characterized. G2-Py-Zn2+was then mixed with chlorinated butyl rubber(CIIR) by a two-roll mill. A series of CIIR/G2-Py-Zn2+elastomers were obtained through vulcanization. CIIR/G2-Py-Zn2+elastomers could achieve high stretchability(a strain of ~1035%), high mechanical strength(a tensile stress of 7.64 MPa). This was benefitted from the friction between G2-Py and CIIR as well as variety of non-covalent bonds provided by G2-Py-Zn2+,which can dissipate energy to further improve the strength and extensibility. The coordination of Zn2+-pyridine was confirmed by Fourier transform infrared spectroscopy, stress relaxation and cycle tensile test. To further investigate the morphology and damping properties of the elastomers, scanning electron microscopy and dynamic mechanical analysis were performed. CIIR-5 showed the best damping performance with higher tan δ_(max) and wider effective damping temperatures. Therefore, this dendrimer modification technology provides wider applications for CIIR elastomers in daily life.

Topological Aspects of Dendrimers via Connection-Based Descriptors

Topological indices(TIs)have been practiced for distinct wide-ranging physicochemical applications,especially used to characterize and model the chemical structures of various molecular compounds such as dendrimers,nanotubes and neural networks with respect to their certain properties such as solubility,chemical stability and low cytotoxicity.Dendrimers are prolonged artificially synthesized or amalgamated natural macromolecules with a sequential layer of branches enclosing a central core.A present-day trend in mathematical and computational chemistry is the characterization of molecular structure by applying topological approaches,including numerical graph invariants.Among topological descriptors,Zagreb connection indices(ZCIs)have much importance.This manuscript involves the establishment of general results to calculate ZCIs,namely first ZCI(FZCI),second ZCI(SZCI),third ZCI(TZCI),modified FZCI,modified SZCI and modified TZCI of two special types of dendrimers nanostars,namely,poly propylene imine octamin(PPIO)dendrimer and poly(propyl)ether imine(PPEtIm)dendrimer.Furthermore,we provide the numerical and graphical comparative analysis of our calculated results for both types of dendrimers with each other.

Dendrimer的模板作用及其在纳米粒子制备中的应用

介绍了dendrimer的模板作用及其用于制备金属、硫化物、合金及高分子等纳米粒子的研究现状,分析了dendrimer的种类和结构、代数、浓度及pH值等对纳米粒子的影响。

应用PAMAM dendrimers作为DNA运送载体的体外研究

StarburstTMPAMAMdendrimers分子是一类新型的高分枝、辐射状对称的树状高分子,在生理条件下其表面具有高密度的正电荷,可以通过静电相互作用与核酸形成复合物后,介导遗传物质进入细胞.研究了G3,G3 5,G5,G7,G7 5,G9各代dendrimers分子与DNA结合后介导其转染细胞的能力,并初步评价这种复合物转染对细胞活力的影响.实验证实,全代的PAMAMdendrmers皆可与DNA结合,并可在体外培养的细胞中介导高效的DNA转染.PAMAMdendrimer/DNA复合物很稳定,在较大的pH值变化范围内(pH 2～ 10 )不解离.PAMAMdendrimers可保护与之复合的DNA分子免受限制性内切酶的降解.在一定的电荷比范围内,高代数的dendrimers分子与DNA形成的复合物对培养细胞的转染效率高于低代数dendrimer分子,复合物所介导的转染效率在不同的细胞系之间也有差异.在有效作用浓度范围内(≤ 1 3× 10 -1g/L),PAMAMdendrimers/DNA复合物对被转染细胞无毒性.但是,未与DNA复合的dendrimers分子在较低浓度时则表现出毒性,表明StarburstTM PAMAMdendrimers分子可作为新型的低毒非病毒DNA载体,用于介导DNA对体外培养细胞的转染.这些前期观察。

纳米材料在基因转染中的应用——Starburst PAMAM dendrimers研究现状

提高重组DNA对培养细胞及活体水平的转染效率是利用重组DNA进行预防和治疗疾病所必须解决的难题之一。一种新型阳离子多聚物———StarburstPAMAMdendrimers的出现为解决现存的难题带来了一线曙光。StarburstPAMAMdendrimers是 1985年之后出现的一类新型星射状树形高分子 ,它们结构规整 ,具有呈辐射状对称的刚性球体结构 ,在生理条件下 ,StarburstPAMAMdendrimers分子具高的表面正电荷密度 ,能与天然状态下存在的带负电荷的生物活性物质 (如核酸 )发生静电相互作用形成复合物。该类树形高分子可极大增强DNA转染真核细胞的转染效率 ,具有许多优于其它现有转染试剂的优良特性 ,并具有在活体内应用的潜力。本文介绍了九十年代以来对该类树形高分子在体外培养细胞及活体水平增强DNA转染效率的研究现状并对今后的研究和应用进行了分析。

Dendrimer的中文名亟需规范统一

树枝状化合物dendrimer因其独特的完美结构以及由此决定的独特性能,在最近20多年里获得了突飞猛进的发展。但关于dendrimer中文名的使用却非常混乱,在中国大陆至少有36种不同的中文名。这种状况严重地阻碍了这门新兴边缘学科在中国的交流与发展,亟需规范统一。综合考虑dendrimer今后在中国的长远发展及名词的实用性等因素,建议将"树状物"作为dendrimer的中文定名。

PAMAM Dendrimers在水／1，2-二氨乙烷界面上的简单离子转移

PAMAM dendrimer是一类三维高度有序的高分子化合物。其具有良好的生物相容性，易于设计，结构上与蛋白质相似，因此在催化、纳米工程、药物设计与运输等方面有广泛的应用。本研究探讨了Dendrimer在液／液界面电化学上的一些性质。

Starburst^(TM) Polyamidoamine Dendrimers介导的绿色荧光蛋白基因在小鼠体内的表达分布及对恶性疟DNA疫苗ES312免疫原性的影响

目的研究StarburstTMPolyamidoamine(PAMAM)dendrimers介导绿色荧光蛋白基因在小鼠体内的表达分布及对恶性疟DNA疫苗ES312免疫原性的影响。方法经股四头肌给小鼠注射StarburstTMPAMAMdendrimers与绿色荧光蛋白基因或恶性疟DNA疫苗ES312的复合物。通过流式细胞术、Westernblot和间接免疫荧光方法检测绿色荧光蛋白的表达分布和表达量。用ELISA方法检测恶性疟DNA疫苗ES312的免疫原性。结果在注射StarburstTMPAMAMdendrimers/DNA复合物后2h～7d内,StarburstTMPAMAMdendrimers携带的绿色荧光蛋白基因的表达在小鼠的心、肝、脾、肺、肾、脑、肌肉中均能被检测到,在肾总蛋白中所占百分比最高,且各器官管腔内皮细胞中的绿色荧光蛋白表达量较高。小鼠的脑和肾中,在StarburstTMPAMAMdendrimers的存在下,绿色荧光蛋白基因的表达量明显高于裸DNA的表达量。经StarburstTMPAMAMdendrimers携带的恶性疟DNA疫苗ES312诱导的抗体反应水平明显高于单纯裸DNA疫苗所诱导的抗体水平。结论StarburstTMPAMAMdendrimers作为一种低抗原性、非病毒的新型DNA载体,能够明显提高裸DNA在体内的表达水平,诱导产生很强的体液免疫反应。但是,StarburstTMPAMAMdendrimers/DNA复合物在各组织器官中的广泛分布,尤其是透过血脑屏障的能力,已超出疫苗载体的适用范围。作为DNA疫苗载体,要对现有StarburstTMPAMAMdendrimers分子的结构做进一步的修饰。

Oxidation of Cyclohexene Catalyzed by PAMAM-SA-M Dendrimers

Oxidation of cyclohexene under 1 atmospheric pressure of molecular oxygen at 70C in the absence of solvent catalyzed by PAMAM-SA-M (Where PAMAM = polyamidoamine; SA = salicyaldehyde; M = metal ions Fe3+, Co2+, Ni2+, Mn2+, Cu2+, Zn2+, respectively) dendrimers, afforded 2-cyclohexen-1-ol 1, 2-cyclohexen-1-one 2, 7-oxabicyclo [4,1,0] heptane 3 and 7-oxabicyl [4,1,0] heptan-2-one 4 as the major products. The factors that affect this reaction are also discussed.

RuRh Bimetallic Nanoparticles Stabilized by 15-membered Macrocycles-terminated Poly(propylene imine) Dendrimer:Preparation and Catalytic Hydrogenation of Nitrile–Butadiene Rubber

A new fourth-generation poly(propylene imine) dendrimer(G4-M) containing 32 triolefinic 15-membered macrocycles on the surfaces has been synthesized. The bimetallic Ru Rh dendrimer-stabilized nanoparticles(DSNs) were first prepared within G4-M by a co-complexation route. The new G4-M dendrimer has been characterized by 1H nuclear magnetic resonance, infrared radiation, and elemental analysis.The dendrimer-stabilized bimetallic ions and reduction courses were analyzed by UV-vis spectroscopy. Highresolution transmission electron microscopy and energy dispersive spectrometer were used to characterize the bimetallic nanoparticle size, size distribution, and particle morphology. The Ru Rh bimetallic DSNs showed high catalytic activity for the hydrogenation of nitrile-butadiene rubber.

Synthesis of carbosilane dendrimers with N,N-dimethylaniline as end groups

Carbosilane dendrimers with 4-bromo-N,N-dimethylaniline as end groups were synthesized from methyltfichlorosilane, aUyl chloride, magnesium and 4-bromo-N,N-dimethylaniline. All compounds were characterized by ^1H NMR, IR, MS.

The Application of Suzuki Coupling Reaction on the Preparation of Carbosilane Dendrimers with 4-(Naphthalen-1-yl)phenyl Core

Carbosilane dendrimers with p-bromophenyl core were synthesized by alternating Grignard and hydrosilylation reaction. And the α-naphthalenyl was connected to the core by the Suzuki coupling reaction. A new carbosilane dendrimer with big π-conjugated structure [4-（naphthalen-l-yl）phenyl core] was given. It shows Suzuki coupling reaction is an effective and powerful core-functionalization method and the satisfactory result can be obtained through prolonging the reaction time with the increase of the generation of dendrimer.

Synthesis and theoretical study of first generation CCK-functional dendrimers

A convenient synthesis and theoretical study of five CCK-functional dendrimers is described. The dendritic cores were linked with the CCK（Trp-Met-Asp（OBn）-PheNH2） fragment by forming amide bonds to give five target molecules. The structures of CCK-functional dendrimers were characterized by NMR, MS spectrum and predicted using molecular mechanics and PM3 semi- empirical molecular orbital theory.

Avidin-dendrimer对Hela细胞的靶向研究

树状大分子对肿瘤有显著的EPR效应,本文在5代聚酰胺-胺类树状大分子表面连接对肿瘤有主动靶向作用的抗生物素蛋白(亲和素),然后用放射性同位素99mTc标记这种兼具被动靶向与主动靶向作用的纳米粒子。Hela细胞体外摄取实验表明连接靶向分子亲和素(Avidin)的Biotin-PAMAM G5-1B4M-99mTc纳米复合物对Hela细胞的摄取远高于未连接靶向分子Avidin的同类纳米粒子。如进一步在小鼠SPECT成像试验中表现出良好的显像效果,这种同位素标记的纳米粒子将有望用于肿瘤的早期诊断或治疗。

Evaluation of Biotinylated PAMAM Dendrimer Toxicity in Models of the Blood Brain Barrier: A Biophysical and Cellular Approach

The interaction of biotinylated G4 poly(amidoamine) (PAMAM) dendrimer conjugates and G4 PAMAM dendrimers with in vitro models of the blood brain barrier (BBB) was evaluated using Langmuir Blodgett monolayer techniques, atomic force microscopy (AFM) and lactate dehydrogenase measures of cell membrane toxicity. Results indicate that both G4 and G4 biotinylated PAMAM dendrimers disrupt the composition of the liquid condensed (LC) and liquid expanded (LE) phases of the 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) lipid monolayer. The disruption is concentration dependent and more marked for G4 biotinylated PAMAMs. Lactate dehydrogenase (LDH) assays using endothelial cell culture models of the BBB indicate that biotinylation results in higher levels of toxicity than non-biotinylation. This approach provides valuable information to assess nanoparticle toxicity for drug delivery to the brain.

Preparation and Properties of Poly(amidoamine) Dendrimer/Quaternary Ammonium Chitosan Hydrogels

A novel quaternary ammonium chitosan hydrogel modified by poly（amidoamine）（PAMAM） dendrimer was prepared by using glutaraldehyde as a cross-linker. The hydrogel was characterized by Fourier transform infrared spectroscopy（FTIR） and scanning electron microscopy（SEM）. The results confirmed its highly porous three-dimensional network structure. The swelling test of hydrogel proved that it had excellent swelling and p H-sensitive properties. The increasing PAMAM content or quaternization degree led to the increase in swelling properties. And the hydrogel with lower cross-linking agent concentration or quaternary ammonium chitosan concentration exhibited better swelling properties. The antibacterial results indicated that with the increase in the PAMAM content, quaternary ammonium chitosan concentration or cross-linking agent concentration, the hydrogels showed better antibacterial activities against both Staphylococcus aureus（S. aureus） and Escherichia coli（E. coli）. Thus, the hydrogel could serve as a promising antibacterial material in the future.

Investigation of the interaction of polyamidoamine dendrimers with nicotinic acid as solubility enhancer

ObjectivePolyamidoamine(PAMAM) dendrimers enhance the solubility of nicotinic acid. MethodsPAMAM dendrimers of generation 1 to 6 were prepared and the effect of pH and concentration of the dendrimers on the solubility enhancement of nicotinic acid was investigated. ResultsThe pH and concentration of the dendrimers influence the solubility enhancement of nicotinic acid. Conclusions Electrostatic interaction between the carboxyl group of the nicotinic acid and the amine groups of the dendrimers is involved.

Convergent synthesis of second generation CCK-functional dendrimers

This paper describes the facile synthesis and characterization of novel dendrimers bearing 9 and 12 CCK peptide fragments on the surface by a convergent method. The structures of dendrimers are characterized by NMR and MS spectrum.

Pentaerythritol-based Carbosilane Dendrimers

A series of novel pentaerythritol-based carbosilane dendrimers have been synthesized. Using pentaerythritol-based tetraallyl ether as core molecule, the dendrimers have been prepared up to the third generation with 108 allyl groups on the periphery by alternate allylation-hydro- silylation approach.