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.

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。

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。

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。

Electrochemistry of polyamidoamine dendrimers ester gel electrolytes

This paper described the first example of polyamidoamine dendrimers ester(PAMAM) used as a gel electrolyte with a short-chain polyethylene glycol (MPEG-400) as aplasticizer. The polymer films are solid and sticky. Background cyclic voltammetry (CV) shows apotential window between +0.7 and -0.7 V vs. Ag/AgCl. The voltammetry of ferrocene and7,7,8,8-tetracyanoquinodimethane (TCNQ) indicates that diffusion coefficients are in the range of10^(-8) -10^(-9) cm^2/s. Ionic conductivities are approximately 10^(-6) S/cm. Similar films usingdimethyl sulfoxide (DMSO) as a plasticizer instead of MPEG-400 have demonstrated ionicconductivities of 10^(-4) S/cm and reversible voltammetry. However, UV spectropho-tometry shows that70% of the DMSO is lost under vacuum, indicating the difficulty in quantifying the DMSO contentwhen exposed to vacuum.

Mechanical Properties of Silicone Rubber Using Carbosilane Dendrimers as the Cross-linker

Peroxide-cured high-temperature vulcanized （HTV） silicone rubber was prepared by using allyl-capped carbosilane dendrimers, in which the core molecule is Si（CHaCH=CH2）4, as the cross-linker. It showed that this kind of allyl-capped carbosilane dendrimer improved the mechanical properties of silicone rubber.

A General Procedure for Surface Modification of Nano-alumina and Its Application to Dendrimers

A general procedure for surface modification of nano-alumina using N, N＇-dicyclohexyl- carbodiimide （DCC） mediated amidation is reported. Aliphatic and aromatic carboxylic acids reacted smoothly with nano-alumina pretreated with 3-aminopropyltriethoxysilane in the presence of DCC, giving modified aluminas having organic surfaces. The grafted aluminas have been characterized qualitatively by FT-IR or ^13C CPMAS NMR spectroscopy, and quantitatively by thermogravimetric analysis and elemental analysis. The procedure was applied to polyether dendrons bearing carboxyl groups at the focal points, giving successful grafting of dendrimers onto nano-alumina.

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.

Synthesis of Novel Dendrimers Containing Amino Acids and Peptides

Some novel peptide dendrimers bearing four amino acids, GD and RGD peptides on their surface were synthesized from tetrakis[（carboxyethoxy）methyl]-methane using DCC method.

Synthesis of PAMAM Dendrimers Bearing BINOL Derivative

New functional dendrimers bearing 4, 8 and 16 axial chiral units on their surface were synthesized from achiral PAMAM dendrimers and axial chiral (R)-BINOL derivative.

Accelerated Approach to the Synthesis of Fluoriated Polyether Dendrimers

Fluorinated polyether dendritic sectors 4, 7 and 10 from the first to the third generations, respectively, were prepared by a convergent approach from readily available pentafluorophenol, phloroglucinol and 1,3-dibromopropane. These dendritic sectors have good solubility properties and are stable in both acidic and basic media. Hence they are useful dendritic building blocks for the preparation of functional dendrimers.

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.

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.

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 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 Preparation of the Carbosilane Dendrimers with Pentafluorophenyl Groups

Polysiloxane was a good solvent for hydrosilation reaction of carbosilane dendrimers with pentafluorophenyl core and HSiMeE（CH2）3C6F5. A new kind of dendrimer with both pentafluorophenyl core and terminal groups was synthesized. The studies showed that with the increase of fluorination, the viscosity values of carbosilane dendrimers decreased.

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.

Synthesis of Calix[4]resorcinarene Core Dendrimers with Peripheral Salicylideneimine Functional Groups

First to third-generation calix[4] resorcinarene core dendrimers, compounds 4a, 4b, 7a, 7b, 10a and 10b, were prepared via the divergent method in seven steps with the corresponding tetraphenyl- and tetra （hydroxyphenyl） calix[4] resorcinarenes （compounds 1a, 1b） as the starting material. The repeat units of the polyamidoamines of these dendrimers were obtained by the ammonolysis of ethyl calixarylacetates 2a and 2b with 1,3-diaminopropane, that is, amide derivatives with terminal amino groups, which in turn reacted with ethyl acrylate to give a higher generation of ester derivatives. The structures of these dendrimers were characterized by IR, ^1H and ^13C NMR spoctrometries. The crystal structure of compound 2b with 12 ethoxycarbonylmethoxy groups was determined by X-ray analysis.

Synthesis of Novel Carbosilane Dendrimers with Myo-inositol Cores

The preparation of carbosilane dendrimers with cores of myo-inositol and the outmost periphery groups of allyl groups has been reported. By using alternate hydrosilylation and alkenylation reactions, the dendrimer have been carried up to the third generation with 48 allyl groups on the periphery.