Spectroelectrochemical analysis of ion-transfer and adsorption of the PAMAM dendrimer at a polarized liquid|liquid interface

The interfacial behavior of the fourth generation polyamidoamine (G4 PAMAM) dendrimer at a water|1,2-dichloroethane (DCE) interface was studied by cyclic voltammetry and potential modulated fluorescence (PMF) spectroscopy. Irregular voltammetric responses were observed at positively polarized interfaces. The cyclic voltammogram was strongly dependent on pH and on the concentrations of the G4 PAMAM dendrimer and the organic supporting electrolyte. PMF spectroscopy was successfully used to analyze the interfacial mechanism of the dendrimer by adding an anionic porphyrin derivative as a fluorescent probe. The results of the PMF measurements demonstrated that the G4 PAMAM dendrimer was transferred across the interface, a process that was accompanied by an adsorption step at pH 7. In contrast, under alkaline conditions, the adsorption process did not seem to be involved in the interfacial behavior.     

苯甲醛修饰的聚酰胺胺树状大分子的合成与荧光性能研究

以乙二胺为中心核,丙烯酸甲酯为支化单体,苯甲醛为端基官能团合成了3.0代和4.0代两种聚酰胺胺-苯甲醛树状大分子。对其荧光性能进行了研究,结果表明,溶液中的Fe3+对不同代数聚酰胺胺-苯甲醛树状大分子的荧光具有淬灭效应,并且荧光发射峰出现了红移现象。溶液中的Zn2+对聚酰胺胺-苯甲醛树状大分子的荧光具有增强作用,但是当Zn2+与树状大分子摩尔比持续增加时,其混合溶液的荧光强度却减小。     

Novel Poly(EThyleneAmidoAmine) (PETAA) dendrimers produced through a unique and highly efficient synthesis

Polyamidoamine (PAMAM) dendrimers have unique attributes that have led to their use in a wide variety of biomedical applications. However, the complex synthesis of this polymer leads to variations in the structure and consistency of the final product, and makes scale-up of manufacturing difficult. This has limited the clinical translation of PAMAM-based materials. Here we describe a rapid and highly efficient two-step method for the synthesis of novel Poly(EThyleneAmidoAmine) (PETAA) dendrimers that have many of the favorable characteristics of PAMAM dendrimers. Generation 0 (G0) to 5 (G5) PETAA dendrimers were synthesized using a 3-(bis(2-(2,2,2,-trifluoroacetamido)ethyl)amino)propanoic acid AB₂ (compound 1) building block via a divergent approach. An ethylenediamine core was coupled with the AB₂ building block via O-(7-Azabenzotriazol-1-yl)N,N,N’,N’-tetramethyluronium hexafluorophosphate (HATU) in the presence of diisopropylethyl amine to give a G0 trifluoroacetamide surface dendrimer. The G0 amine surface dendrimer was then obtained by treating the G0 trifluoroacetamide surface dendrimer with potassium carbonate. Repetitions of these two coupling/deprotection reactions were then used to build the dendrimer by coupling the surface amino groups to the carboxyl moiety of the AB₂ building block, followed by the deprotection step with potassium carbonate. The resulting PETAA dendrimers have the same number of surface primary amino groups, the same number of chemical bonds between the dendrimer core and the surface, and the same number of tertiary amino groups throughout the structures as similar generations of PAMAM dendrimers. In contrast, the structure of the PETAA dendrimers is more complete and more uniform than PAMAM dendrimers, especially at higher generations. This unique synthetic process for PETAA dendrimers also offers the potential for large-scale production, therefore providing inherently more uniform and complete structures for exacting biomedical applications.     

酯端基型聚酰胺胺树形高分子对聚(3-羟基丁酸戊酸共聚酯)结晶性能的影响

采用不同比例G3.5酯端基类型的聚酰胺胺(PAMAM)树形高分子氯仿溶液与聚(3-羟基丁酸酯-co-3-羟基戊酸酯)(PHBV)树脂氯仿溶液进行共混并流延成膜,采用差示扫描量热分析、偏光显微镜以及拉伸和直角撕裂等方式对制备的PHBV/PAMAM复合膜进行表征。结果表明,随着PAMAM树形高分子的加入,PHBV/PAMAM复合膜的玻璃化转变温度（Tg）越来越明显,初步表明其韧性增强; G3.5 PAMAM树形高分子的加入,可使PHBV的结晶度由61.70 %先下降至24.02 %,并逐渐下降,最后至结晶消失; PAMAM树形高分子的加入可使PHBV的直角撕裂强度大幅度提高,最高可由8.90 kN/m提高到22.10 kN/m;当PAMAM树形高分子含量为2.0份时,增韧效果最好。     

LDL adsorbent with dendrimer PAMAM as spacer

Dendritic polymers are three-dimensional, highly ordered compounds formed by reiterative reaction sequences, and via discrete stages referred to as generations. To study the spacer effect of low density lipoprotein (LDL) adsorbent, we linked dendrimer polyamidoamine (PAMAM) generation 1 (G1), generation 3 (G3) and generation 5 (G5) to cellulose beads, respectively, and then determined the adsorption proportion of the adsorbents with PAMAM decorated with taurine. The result shows that the spacer with activated multi-points could efficiently improve the adsorption capacity of the adsorbent. __________ Translated from Ion Exchange and Adsorption, 2008, 24(1): 1–9 [译自: 离子交换与吸附]     

Gelation and swelling behavior of end-linked hydrogels prepared from linear poly(ethylene glycol) and poly(amidoamine) dendrimers

Linear α,ω di-epoxide-terminated poly(ethylene glycol) of molar mass 4000 g mol⁻¹ was end-linked with amine-terminated poly(amidoamine) (PAMAM) dendrimers of generations 0, 2, and 4 in water to prepare architecturally well-defined copolymer hydrogels. The gelation and equilibrium swelling of the gels in water were characterized while systematically varying the polymer concentration at preparation, dendrimer generation, and mole ratio of dendrimer endgroups to PEG endgroups. The Ahmad-Rolfes-Stepto (ARS) theory of non-linear polymerization was applied to predict conditions favoring gelation, and to estimate the extent of reaction of amine and epoxide groups. Hydrogels having a large stoichiometric excess of amines over epoxides exhibited “superabsorbent” behavior upon extraction and equilibrium swelling in pure water. The mole ratio of amines to epoxides (equivalently, the mass fraction of dendrimers) was the most important factor governing superabsorbent behavior, although the polymer volume fraction at crosslinking and dendrimer generation also affected swelling to a lesser extent. The superabsorbency arises in part from protonation of the dendrimer amine endgroups at external pH = 7, which is supported by the drastic shrinkage of the most highly swelling gels in aqueous NH₄OH at pH = 11. Equilibrium swelling at pH = 7 was noticeably enhanced in gels having a high soluble fraction and high mass fraction of dendrimers. End-linking of linear polymer precursors to PAMAM dendrimers can potentially produce novel copolymer gels that combine attractive properties of the linear precursors with high swelling and pH-responsive behavior of PAMAM-containing networks.     

PAMAM树状大分子负载和释放阿霉素的耗散粒子动力学模拟

采用耗散粒子动力学模拟方法研究了药物输送载体聚酰胺-胺（PAMAM）树状大分子对抗癌药物阿霉素（DOX）的负载和释放行为。构建了PAMAM树状大分子的粗粒化模型,该模型能准确地重现树状大分子的构象性质。考察了PAMAM树状大分子代数（G）对DOX负载以及pH环境对DOX释放的影响。模拟结果表明,PAMAM树状大分子主要通过疏水作用将DOX包封于内部空腔,G6和G7 PAMAM树状大分子的负载能力较强,因为其孔隙率较高,内部有更多的疏水空腔。在低pH环境下,PAMAM树状大分子结构发生变化,DOX分子能快速地从其中释放,主要原因是PAMAM的伯胺、叔胺和DOX伯胺发生质子化,质子化基团间的静电排斥作用使得PAMAM树状大分子发生溶胀,导致其内部空腔暴露,促进了DOX的释放。本工作可以为基于树状大分子的药物输送体系的设计和优化提供参考。     

Binding properties of polyamidoamine dendrimers

Dendrimers are globular, hyperbranched polymers possessing a high concentration of surface functional groups and internal cavities. These unique features make them good host molecules for small ligands. To reveal relationships between dendrimer size and its encapsulating properties, the interactions of the fourth and the sixth generations of polyamidoamine dendrimers (PAMAM G4 and PAMAM G6) with a fluorescent dye 1‐anilinonaphthalene‐8‐sulfonate (ANS) were studied. Because ANS is a fluorescent molecule and its fluorescence is very sensitive to changes in its microenvironment, it was possible to use spectrofluorometric methods to evaluate the interactions with dendrimers. A double fluorometric titration method was used to estimate a binding constant and the number of binding centers. There were two types of dendrimer binding centers characterized by different affinity towards ANS. For PAMAM G4, the values of K_b and n for low‐affinity and high‐affinity sites equaled to 2.6 × 10⁵, 0.60 and 3.70 × 10⁶, 0.34, respectively, whereas in the case of PAMAM G6, these values equaled to 1.2 × 10⁵, 76.34 and 1.38 × 10⁶, 22.73. It was observed that the size of the dendrimer had a strong impact on the number of ANS molecules that interacted with dendrimers and their location within the macromolecule. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2036–2040, 2007     

Poly(amidoamine) Dendrimers as Nanocarriers for 5-Fluorouracil: Effectiveness of Complex Formation and Cytotoxicity Studies

Two generations of positively charged poly(amidoamine) dendrimers (PAMAMs) were selected for study as potential carriers for the anticancer drug 5-fluorouracil (5FU), a drug primarily used in the treatment of colorectal cancer. Analytical techniques, such as UV-Vis spectrophotometry, NMR Spectroscopy and Laser Doppler Velocimetry (LDV), have shown that the most critical factor determining the formation of a PAMAM–5FU complex is the starting components’ protonation degree. The tests confirmed the system’s ability to attach about 20 5FU molecules per one dendrimer molecule for the G4PAMAM dendrimer and about 25 molecules for the G6PAMAM dendrimer, which gives a system yield of 16% for the fourth generation and 5% for sixth generation dendrimers. Additionally, using the QCM-D method, the adsorption efficiency and the number of drug molecules immobilized in the dendrimer structure were determined. A new aspect in our study was the determination of the change in zeta potential (ζ) induced by the immobilization of 5FU molecules on the dendrimer’s outer shell and the importance of this effect in the direct contact of the carrier with cells. Cytotoxicity tests (resazurin reduction and MTS tests) showed no toxicity of dendrimers against mouse fibroblast cells (L929) and a significant decrease in cell viability in the case of four human malignant cell lines: malignant melanoma (A375), glioblastoma (SNB-19), prostate cancer (Du-145) and colon adenocarcinoma (HT-29) during incubation with PAMAM–5FU complexes. The purpose of our work was to investigate the correlation between the physicochemical properties of the carrier and active substance and the system efficiency and optimizing conditions for the formation of an efficient system based on PAMAM dendrimers as nanocarriers for 5-fluorouracil. An additional aspect was to identify potential application properties of the complexes, as demonstrated by cytotoxicity tests.     

树枝状分子的快速合成及在保湿剂和洗涤剂中的应用

以丙烯酸甲酯和乙二胺为原料,通过Michael加成和氨解重复反应合成了以乙二胺为核的0．5G～3．5G的聚酰胺——胺树枝状分子。利用提高反应温度来加快反应速度,实现了聚酰胺——胺树枝状分子的快速合成。测试了整代树枝状分子的保湿性能及半代树枝状分子的去污性能。并用红外表征对快速合成产物与低温合成产物进行了比较。     

Preparation of CaCO3/polymer composite films via interaction of anionic starburst dendrimer with poly(ethylenimine)

Summary The CaCO₃/poly(ethylenimine) composite film was obtained in the presence of anionic poly(amidoamine) (PAMAM) dendrimer (G=3.5), whereas the formation of composite film was not observed without PAMAM dendrimer or with PAMAM dendrimer (G=1.5) judging from the results of scanning electron micrographs (SEM). The crystal phase of the CaCO₃ film formed was found to be calcite by FT-IR and XRD analysis. The adsorption of PAMAM dendrimer on poly(ethylenimine) film might cause local high concentration of calcium ion and induce a formation of the CaCO₃ film. Received: 23 October 2000/Accepted: 10 November 2000     

Poly(amidoamine) dendritic structures,bearing different end groups,as adhesion promoters for urea–formaldehyde wood adhesive system

A series of core‐shell poly(amidoamine) (PAMAM) dendritic compounds bearing different end groups such as  OH, NH₂, and NH₃⁺⁻Cl up to the third generation were prepared via successive Michael addition of a nucleophilic core (ethylenediamine) to methylacrylate followed by amination steps using ethylenediamine for the amine‐terminated while ethanolamine for the hydroxyl‐terminated compounds, also the protonated ammonium salt terminated form was obtained by cationization of the amine‐terminated form using hydrochloric acid solution. The Surface activity and aggregation behavior of the corresponding aqueous solutions of the prepared generations with their different end groups were studied and confirmed by surface tension measurements using ring method technique. The prepared dendrimers showed high surface activity and the measurements revealed their ability to self aggregate in water at very low concentrations, critical aggregation concentrations (CACs). The CACs were found to decrease with increasing the generation number, which implies that molecular weight and structure play important rules in controlling the surface activity and CAC. The dendritic compounds proved to be effective as adhesion promoters for urea formaldehyde (UF) resins when applied as wood adhesive systems, which was ascribed in partial to the improved wetting over the substrate, a role that is fundamentally related to the huge number of function groups present at the interface. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

荧光性聚酰胺-胺树形分子在潜指纹显现中的应用研究

本文系统研究了不同条件(树形分子代数、浓度、浸泡时间等)下荧光性聚酰胺-胺树形分子(PAMAM)水溶液作为荧光探针对锡纸、透明胶带等基底上油印潜指纹的显现效果.结果发现PAMAM树形分子可以和指纹残留物进行靶向结合.结合到指纹纹线上的该荧光性纳米材料在暗室中365 nm紫外光的激发下发出明亮的蓝色荧光,指印纹线与基底反差大、指纹易于辨认,且操作简单,试剂完全环保无污染.这些结果表明PAMAM水溶液是一种潜在的优良的指纹显现试剂.最后,把PAMAM树形分子水溶液对指纹的显现效果进行量化处理,乳突纹与基底间的灰度对比度达到90%以上.     

树枝形聚酰胺胺对尼龙6性能影响的研究

研究4．0代树枝形聚酰胺胺（PAMAM）对尼龙6拉伸性能、冲击性能及熔体流动速率的影响。结果发现，在尼龙6中添加PAMAM后，尼龙6的拉伸强度、断裂伸长率、缺口冲击强度及熔体流动速率均有所提高，PAMAM添加量为1．0％时效果最佳。PAMAM与尼龙6之间强烈的相互作用，以及两相界面上形成的密实薄层，是尼龙6力学性能提高的原因。     

一种聚酰胺胺-苯甲醛树状大分子的合成及其荧光性能

首先以乙二胺为中心核,丙烯酸甲酯为支化单体合成了2.0代的聚酰胺胺树状大分子(PAMAM G 2.0),然后同苯甲醛在60℃水浴恒温反应48 h,得到了一种聚酰胺胺-苯甲醛树状大分子,用FTIR1、HNMR和13CNMR表征了合成产物的分子结构,结果和设计一致。该树状大分子能溶解于三氯甲烷,不溶于水、环己烷。对其荧光性能进行了研究,结果表明,溶液中的Fe3+对聚酰胺胺-苯甲醛树状大分子的荧光具有猝灭效应,并且荧光发射峰从436 nm红移到458 nm;溶液中的Zn2+对聚酰胺胺-苯甲醛树状大分子的荧光具有增强作用,同时荧光发射峰从436 nm蓝移到402 nm。     

Hydrothermal-Freeze-Casting of Poly(amidoamine)-Modified Graphene Aerogels towards CO2 Adsorption

This article presents novel poly(amidoamine) (PAMAM) dendrimer-modified with partially-reduced graphene oxide (rGO) aerogels, obtained using the combined solvothermal synthesis-freeze-casting approach. The properties of modified aerogels are investigated with varying synthesis conditions, such as dendrimer generation (G), GO:PAMAM wt. ratio, solvothermal temperature, and freeze-casting rate. Scanning electron microscopy, Fourier Transform Infrared spectroscopy, Raman spectroscopy, X-ray photoelectron spectroscopy are employed to characterize the aerogels. The results indicate a strong correlation of the synthesis conditions with N content, N/C ratio, and nitrogen contributions in the modified aerogels. Our results show that the best CO₂ adsorption performance was exhibited by the aerogels modified with higher generation (G7) dendrimer at low GO:PAMAM ratio as 2:0.1 mg mL⁻¹ and obtained at higher solvothermal temperature and freeze-casting in liquid nitrogen. The enclosed results are indicative of a viable approach to modify graphene aerogels towards improving the CO₂ capture.     

树状分子PAMAM接枝改性纳米SiO2与尼龙6的原位复合

将树状分子PAMAM接枝改性的纳米Si02与尼龙6进行原位复合，测试了复合材料的各项性能，对树状分子改性无机纳米粒子进行了初步的探索。结果表明：PAMAM接枝改性纳米SiO2可以提高尼龙6的强度、刚性和非等温结晶能力，但材料的韧性在接枝PAMAM代数较高的情况下趋于降低，同时，基体的摩尔质量显著下降。     

萘修饰的树枝形聚酰胺-胺的合成与荧光性质研究

在DMF溶剂中使用不同代数的整代树枝形聚合物聚酰胺-胺(PAMAM)与1,8-萘二甲酸酐进行酰胺化反应,制备了1,8-萘酰亚胺修饰的3.0G以及5.0G的树枝形聚合物D3、D5。对产物进行红外、紫外-可见吸收、荧光发射、激发光谱以及元素分析的表征,产物与目标产物结构一致。在氯仿与乙醇(体积比为1∶1)的混合溶剂中,由于PAMAM对萘环的固定作用,在萘环浓度相同的情况下,1,8-萘二甲酸酐不形成激发态萘环与基态萘环的激基缔合物,而聚合物D形成了分子内萘环的激基缔合物,在471 nm处产生萘环激基缔合物的荧光发射峰,具有潜在的应用价值。     

端氨基树枝状大分子/环氧树脂体系固化动力学的FTIR研究

用傅立叶变换红外光谱(FTIR)法研究了双酚A二缩水甘油醚环氧树脂(GEBA)用低代端氨基聚(酯-胺)树枝状大分子G1.0(NH2)3、G1.5(NH2)8和聚(胺-酰胺)树枝状大分子PAMAM1.0(NH2)4作为固化剂的等温固化动力学,得到了不同温度下转化率与固化时间及反应速率与固化时间的关系.与小分子固化剂相比,端氨基树枝状大分子作固化剂时环氧基转化率在反应开始时增长得更快,较高代树枝状大分子在高温下固化环氧树脂时尤其如此.在相同温度和时间下,PAMAM1.0(NH2)4/DGEBA、G1.0(NH2)3/DGEBA、G1.5(NH2)8/DGEBA体系的转化率依次增大.进一步估算了3个体系在一定转化率下的固化反应表观活化能.在相同转化率时,用G1.5(NH2)8、PAMAM1.0(NH2)4、G1.0(NH2)3作固化剂的体系表观活化能依次减小.