无机纳米粒子表面修饰

在讨论无机纳米粒子团聚机理的基础上综述了纳米粒子表面修饰研究进展。表面修饰包括物理和化学修饰,重点综述了表面聚合物修饰最新研究进展。介绍了以化学键在纳米粒子表面接枝聚合物,其主要方法包括在无机纳米粒子表面引入可聚合碳-碳双键合成大分子单体、此大分子单体与相应乙烯基单体共聚在表面生成聚合物;将引发剂"固定"在纳米粒子表面合成大分子引发剂,以此引发剂引发单体聚合物生成表面接枝聚合物;反应型聚合物链与粒子表面活性基团反应将聚合物链接枝到纳米粒子表面。     

VPE引发的苯乙烯无皂乳液聚合研究

利用偶氮型聚乙二醇大分子引发剂(VPE)引发苯乙烯进行无皂乳液聚合,制得了颗粒形态规整、单分散性较好的共聚物纳米微球.通过透射电子显微镜(TEM)和激光光散射(LLS)对微球的形态、粒径大小与分布进行了表征,同时考察了大分子引发剂VPE用量对聚合物纳米微球的粒径和聚合物乳液粘度的影响.实验结果表明:当苯乙烯的浓度固定在0.385mol/L时,随着VPE的浓度从1.2mmol/L增加到4.8mmol/L,聚合物纳米微球的粒径从178nm减少到70nm,而聚合物乳液的黏度相应从1.93mpa·s增加到2.17mpa·s,说明微球粒径在一定范围内可控.由嵌段共聚物的结构可推测该聚合物纳米微球的形成机理与传统乳液聚合体系不同,属于自组装成核,形成的微球具有核壳结构,这提供了一种简便制备嵌段共聚物纳米微球的方法.     

树枝状大分子改性聚乙二醇生物材料的制备与研究

采用了新的"酸酐法"使用2,2-二羟甲基丙酸(DMPA)来合成一种具有规整结构树枝状大分子.制备好的树枝状大分子通过高效酯化反应接枝到聚乙二醇(PEG)两端,形成结构高度支化、表面官能团密度大、单分散性的大分子.树枝状大分子的制备过程中的分步提纯进行彻底,反应物在高效催化剂(DMAP)的存在下反应活性大,反应完全,得到的产物极其规整.之后用一步合成方法得到了树枝状大分子-聚乙二醇-树枝状大分子(dendrimers-PEG-dendrimers)的聚合物.通过红外光谱(FTIR)、核磁共振氢谱(1H-NMR)、凝胶渗透色谱(GPC)对聚合物及其中间产物的表征表明,合成的高分子结构严密地与理论相吻合.     

Pickering细乳液法制备无机聚合物复合中空微球

采用有机胺催化水解正硅酸乙酯生成SiO_2纳米粒子,经硅烷偶联剂改性后,获得了两亲性的SiO_2纳米粒子。以其作为Pickering乳化剂,成功制备了稳定的Pickering细乳液并合成了无机聚合物复合中空微球。通过红外光谱、透射电镜、扫描电镜和热重分析等测试手段对复合中空微球进行了表征。结果表明:引发剂为偶氮二异庚腈、交联剂用量为0.2%时合成了直径在1.5~2μm之间的复合中空微球。采用低温引发剂有利于合成均一粒径的中空微球;交联剂的用量能够改变微球的粒径大小;不同的单体类型会影响微球的粒径分布。     

利用开环聚合和原子转移自由基聚合在纳米二氧化硅表面接枝聚合物

利用硅烷偶联剂KH-550处理纳米二氧化硅(SiO_2)表面,得到氨基化的SiO_2,再通过溴异丁酸缩水甘油酯与氨基的开环反应,在SiO_2表面同时键接了开环聚合(ROP)的引发剂-OH和原子转移自由基聚合(ATRP)的引发剂-Br(SNPs-fOH/Br)。以SNPs-f-OH/Br为引发剂,分别进行ROP和ATRP,在纳米SiO_2表面接枝了聚己内酯(PCL)和聚苯乙烯(PS)混合聚合物刷(Mixed brush)。采用红外光谱、透射电镜、热失重、凝胶渗透色谱等方法对所得到的复合粒子进行了表征和测试。研究结果表明,混合聚合物刷成功接枝到了纳米SiO_2表面,通过控制聚合时间可以控制2种接枝聚合物的相对分子质量。本方法为纳米粒子表面接枝混合聚合物刷提供了一种简便的方法。     

纳米铜/PMMA-b-PS的超声合成及有序组装

在超声辐射作用下,以α-溴代丙酸乙酯为引发剂,溴化亚铜/2,2-联吡啶为催化体系,通过原子转移自由基聚合(A-TRP)制备了分子链末端含有一个α-溴原子的聚甲基丙烯酸甲酯(PMMA-Br)。以此为大分子引发剂引发苯乙烯单体进行ATRP反应,制得聚甲基丙烯酸甲酯嵌段聚苯乙烯(PMMA-b-PS)共聚物。通过硼氢化钠还原聚合物体系中的溴化亚铜,从而得到纳米铜/PMMA-b-PS复合粒子。红外光谱(FT-IR)和核磁共振(1H-NMR)表征嵌段共聚物的结构;凝胶渗透色谱(GPC)测定了共聚物的相对分子量和多分散系数;X射线光电子能谱(XPS)证明纳米铜和PMMA-b-PS嵌段共聚物中PMMA之间存在一定的相互作用;通过高分辨透射电子显微镜(HTEM)观察到纳米铜具有诱导聚合物组装的现象。     

ATRP方法可控合成碳纳米管/PMMA纳米复合材料

通过多壁碳纳米管的表面改性合成了ATRP引发剂,利用合成的ATRP引发剂进行ATRP活性聚合,成功地在碳纳米管表面接枝聚合物PMMA。利用红外(IR)、透射电镜(TEM)、热重(TGA)以及核磁共振(NMR)表征接枝的碳纳米管,考察了碳纳米管用量对碳纳米管/PMMA纳米复合材料力学性能的影响,结果表明,碳纳米管表面成功接枝聚合物PMMA,PMMA的力学性能得到很大改善。     

Mg(OH)_2-PMMA复合粒子的制备及表征EI北大核心

为了减小纳米氢氧化镁较严重的团聚问题,通过在氢氧化镁表面接枝大分子聚甲基丙烯酸甲酯(PMMA)来制备氢氧化镁/PMMA纳米复合粒子,以提高纳米复合粒子在有机相中的相容性和分散性。首先,通过油酸对氢氧化镁进行表面修饰,在其表面引入双键烯烃基团,然后以丙烯酸甲酯(MMA)为单体,偶氮二异丁腈(AIBN)为引发剂,聚乙烯吡咯烷酮(PVP)为稳定剂,通过分散聚合的方法在修饰过的氢氧化镁表面接枝有机大分子PMMA。通过XRD、FT-IR、TGA、FESEM、EDS和沉降实验对所得Mg(OH)2/PMMA纳米复合粒子进行了测试表征,结果表明:有机大分子PM-MA成功地接枝在了油酸修饰后的Mg(OH)2表面上,纳米复合粒子在有机相中的分散性和相容性都得到了很大的提高。     

亲油性金纳米粒子的合成

利用相转移法成功地合成了粒径在2～7nm的硫醇表面修饰Au纳米粒子.采用透射电子显微镜、纳米粒度分布仪、红外光谱分析仪等现代测试技术对所合成的Au纳米粒子进行了表征.结果表明,表面为硫醇所修饰的Au纳米粒子,在有机溶剂中具有很好的分散性,表面修饰层的存在不仅有效地阻止Au纳米粒子的团聚,而且使得纳米粒子粒径分布窄,粒径可控.     

雾化-热分解法合成氧化铁纳米粒子及其磁性能

建立了将五羰基铁超声雾化、分段加热分解-氧化及产物收集-修饰一体化的氧化铁纳米粒子合成装置,研究了不同温度参数对纳米粒子的相组成和形貌的影响,并通过在雾化液及收集液中添加修饰剂以控制合成纳米粒子的粒径和分散性。采用XRD、TEM和SQUID对合成的纳米粒子进行了表征。成功合成了不同结晶性和分散性的球形γ-Fe2O3纳米粒子。随着粒径减小,合成纳米粒子由顺磁性过渡到超顺磁性。     

Nanomechanical properties of hydroxyapatite (HAP) with DAB dendrimers (poly-propylene imine) coatings onto titanium surfaces

Coatings of hydroxyapatite (HAP) nanorods onto titanium surfaces were synthesized with the aim to improve coatings’ mechanical properties and adhesion to the substrate. The coatings are consisting of HAP nanorods synthesized in the presence of a cationic fourth generation diaminobutane poly(propylene imine) dendrimer (DAB) bearing 32 amine end groups employing varying calcium: dendrimer ratios and varying hydrothermal treatments. The quality, surface morphology and structure of the coatings were characterized with X-ray diffraction, thermogravimetric analysis, scanning electron microscopy and energy dispersive microanalysis. Wear resistance and adhesion properties of the coatings onto titanium substrates were studied through nanoindentation analysis. The experimental conditions, namely the calcium: dendrimer molar ratio and the hydrothermal treatment temperature were carefully selected; thus, it was possible to produce coatings of high hardness and elastic modulus values (ranging between 1–4.5 GPa and 40–150 GPa, respectively) and/or high wear resistance and plastic deformation values.     

Optimization of carboxylate-terminated poly(amidoamine) dendrimer-mediated cisplatin formulation

Cisplatin is mainly used in the treatment of ovarian, head and neck and testicular cancer. Poor solubility and non-specific interactions causes hurdles in the development of successful cisplatin formulation. There were few reports on poly(amidoamine) (PAMAM) dendrimer–cisplatin complexes for anticancer treatment. But the earlier research was mainly focused on therapeutic effect of PAMAM dendrimer–cisplatin complex, with less attention paid on the formulation development of these complexes. Objective of the present study is to optimize and validate the carboxylate-terminated, EDA core PAMAM dendrimer-based cisplatin formulation with respect to various variables such as dendrimer core, generation, drug entrapment, purification, yield, reproducibility, stability, storage and in-vitro release. Dendrimer–cisplatin complex was prepared by an efficient method which significantly increases the % platinum (Pt) content along with the product yield. Dendrimers showed reproducible (～27%) platinum loading by weight. Variation in core and generations does not produce significant change in the % Pt content. Percentage Pt content of dendrimeric formulation increases with increase in drug/dendrimer mole ratio. Formulation with low drug/dendrimer mole ratio showed delayed release compared to the higher drug/dendrimer mole ratio; these dendrimer formulations are stable in room temperature. In vitro release profiles of the stored dendrimer–cisplatin samples showed comparatively slow release of cisplatin, which may be due to formation of strong bond between cisplatin and dendrimer. This study will contribute to create a fine print for the formulation development of PAMAM dendrimer–cisplatin complexes.     

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

Nano-Micro Letters - A new fourth-generation poly(propylene imine) dendrimer (G4-M) containing 32 triolefinic 15-membered macrocycles on the surfaces has been synthesized. The bimetallic...     

A novel dendrimer based on poly (L-glutamic acid) derivatives as an efficient and biocompatible gene delivery vector

Non-viral gene delivery systems based on cationic polymers have faced limitations related to their relative low gene transfer efficiency, cytotoxicity and system instability in vivo. In this paper, a flexible and pompon-like dendrimer composed of poly (amidoamine) (PAMAM) G4.0 as the inner core and poly (L-glutamic acid) grafted low-molecular-weight polyethylenimine (PLGE) as the surrounding multiple arms was synthesized (MGI dendrimer). The novel MGI dendrimer was designed to combine the merits of size-controlled PAMAM G4.0 and the low toxicity and flexible chains of PLGE. In phosphate-buffered saline dispersions the well-defined DNA/MGI complex above a N/P ratio of 30 showed good stability with particle sizes of approximately 200 nm and a comparatively low polydispersity index. However, the particle size of the DNA/25 kDa polyethylenimine (DNA/PEI 25K) complex was larger than 700 nm under the same salt conditions. The shielding of the compact amino groups at the periphery of flexible PAMAM and biocompatible PLGE chains in MGI resulted in a dramatic decrease of the cytotoxicity compared to native PAMAM G4.0 dendrimer. The in vitro transfection efficiency of DNA/MGI dendrimer complex was higher than that of PAMAM G4.0 dendrimer. Importantly, in serum-containing medium, DNA/MGI complexes at their optimal N/P ratio maintained the same high levels of transfection efficiency as in serum-free medium, while the transfection efficiency of native PAMAM G4.0, PEI 25K and Lipofectamine 2000 were sharply decreased. In vivo gene delivery of pVEGF165/MGI complex into balloon-injured rabbit carotid arteries resulted in significant inhibition of restenosis by increasing VEGF165 expression in local vessels. Therefore, the pompon-like MGI dendrimer may be a promising vector candidate for efficient gene delivery in vivo.     

Photolithographic patterning of dendrimer monolayers and pattern-selective adsorption of linear macromolecules

Alkyl groups of n-octadecyltrimethoxysilane (ODS) in a self-assembled monolayer on a silicon substrate were oxidized to carboxyl groups by partial irradiation of vacuum ultra-violet light under the photomask, producing a COOH/ODS line pattern. After active esterification of carboxyl groups, two kinds of amine-terminated dendrimers, poly(propyleneimine) and poly(amido amine) (PAMAM) dendrimers, were immobilized on a COOH line through amide-bond so that photolithographic dendrimer/ODS pattern was finally fabricated. Preparation was certified by atomic force microscopy (AFM) and surface-enhanced infrared absorption spectroscopy at transmission mode. Adsorption of linear macromolecules was examined on PAMAM dendrimer/ODS pattern. After adsorption of poly-L-glutamic acid (PGA) at a pH below alpha-helix--random coil transition, rod-shape texture was observed only on the dendrimer line in an AFM image. This texture is an aggregate of alpha-helical PGA. Sodium hyaluronate and DNA were also adsorbed selectively on the dendrimer line, keeping the line profile, although characteristic textures were not observed.     

Direct electrochemistry of laccase immobilized on au nanoparticles encapsulated-dendrimer bonded conducting polymer: application for a catechin sensor

The direct electrochemistry of laccase was promoted by Au nanoparticle (AuNP)-encapsulated dendrimers (Den), which was applied for the detection of catechin. To increase the electrical properties, AuNPs were captured in the interiors of the dendrimer (Den-AuNPs) as opposed to attachment at the periphery of dendrimer. To prepare Den-AuNPs, the Au(III) ions were first coordinated in the interior of dendrimer with nitrogen ligands and then reduced to form AuNPs. The size of AuNPs encapsulated within the interior of the dendrimer was determined to be 1.7 +/- 0.4 nm. AuNPs-encapsulated dendrimers were then used to covalently immobilize laccase (PDATT/ Den(AuNPs)/laccase) through the formation of amide bonds between carboxylic acid groups of the dendrimer and the amine groups of laccase. Each layer of the PDATT/Den(AuNPs)/laccase probe was characterized using CV, EIS, QCM, XPS, SEM, and TEM. The PDATT/Den(AuNPs)/laccase probe displayed a well-defined direct electron-transfer (DET) process of laccase. The quasi-reversible redox peak of the Cu redox center of the laccase molecule was observed at -0.03/+0.13 V vs Ag/AgCl, and the electron-transfer rate constant was determined to be 1.28 s (-1). A catechin biosensor based on the electrocatalytic process by direct electrochemistry of laccase was developed. The linear range and the detection limit in the catechin analysis were determined to be 0.1-10 and 0.05 +/- 0.003 microM, respectively. Interference effects from various phenolic and polyphenolic compounds were also studied, and the general applicability of the biosensor was evaluated by selective analysis of real samples of catechin.     

智能光度滴定仪及其在酸碱滴定中的应用

由便携式光谱测定仪（POPS-15）和数字滴定管（DAB-1）组成的智能光度滴定仪实现了滴定过程的全谱适时监测,系统能根据三维滴定曲线自动判定滴定终点,自动给出测定结果。酸碱滴定的标准偏差为0．014mL。     

Large-scale dendrimer-based uneven nanopatterns for the study of local arginine-glycine-aspartic acid （RGD） density effects on cell adhesion

Cell adhesion processes are governed by the nanoscale arrangement of the extracellular matrix （ECM）, being more affected by local rather than global concentrations of cell adhesive ligands. In many cell-based studies, grafting of dendrimers on surfaces has shown the benefits of the local increase in concentration provided by the dendritic configuration, although the lack of any reported surface characterization has limited any direct correlation between dendrimer disposition and cell response. In order to establish a proper correlation, some control over dendrimer surface deposition is desirable. Here, dendrimer nanopatterning has been employed to address arginine-glycine-aspartic acid （RGD） density effects on cell adhesion. Nanopatterned surfaces were fully characterized by atomic force microscopy （AFM）, scanning tunneling microscopy （STM） and X-ray photoelectron spectroscopy （XPS）, showing that tunable distributions of cell adhesive ligands on the surface are obtained as a function of the initial dendrimer bulk concentration. Cell experiments showed a clear correlation with dendrimer surface layout： Substrates presenting regions of high local ligand density resulted in a higher percentage of adhered cells and a higher degree of maturation of focal adhesions （FAs）. Therefore, dendrimer nano- patterning is presented as a suitable and controlled approach to address the effect of local ligand density on cell response. Moreover, due to the easy modification of dendrimer peripheral groups, dendrimer nanopatterning can be further extended to other ECM ligands having density effects on cells.     

Improved adhesion of Au thin films to SiOx/Si substrates by dendrimer mediation

Quantitative evidence of significantly improved interfacial adhesion between Au films and SiO_x/Si substrates induced by an organic dendrimer monolayer was presented. For dendrimer-mediated Au films, nanoscratch tests revealed a critical load that was two times higher than that for films without dendrimer mediation. Atomic force microscopy (AFM) examination of nanoindents revealed much constrained lateral flow of metals in the dendrimer-mediated Au films during nanoindentation, indicating enhanced adhesion due to the presence of the dendrimer layer.     

Silver/dendrimer nanocomposites as biomarkers: fabrication, characterization, in vitro toxicity, and intracellular detection

We have synthesized water-soluble, biocompatible, fluorescent, and stable silver/dendrimer nanocomposites that exhibit a potential for in vitro cell labeling. Amino-, hydroxyl-, and carboxyl-terminated ethylenediamine core generation 5 poly(amidoamine) dendrimers were utilized to prepare aqueous silver(I)-dendrimer complexes (with the molar ratio of 25 Ag+ per dendrimer) at the biologic pH of 7.4. Conversion of silver(I)-dendrimer complexes into dendrimer nanocomposites was achieved by irradiating the solutions with UV light to reduce the bound Ag+ cations to zerovalent Ag0 atoms, which were simultaneously trapped in the dendrimer network, resulting in the formation of {(Ag0)25-PAMAM_E5.NH2}, {(Ag0)25-PAMAM_E5.NGly}, and {(Ag0)25-PAMAM_E5.NSAH} dendrimer nanocomposites (DNC), respectively. The silver-DNCs were characterized by means of UV-vis, fluorescence spectroscopy, dynamic light-scattering, zeta potential measurements, high-resolution transmission electron microscopy, X-ray energy dispersive spectroscopy, and selected area electron diffraction. The cytotoxicity of dendrimers and related silver nanocomposites was evaluated using an XTT colorimetric assay of cellular viability. The cellular uptake of nanoparticles was examined by transmission electron and confocal microscopy. Results indicate that {(Ag0)25-PAMAM_E5.NH2}, {(Ag0-)25-PAMAM_E5.NGly}, and {(Ag0)25-PAMAM_E5.NSAH} form primarily single particles with diameters between 3 and 7 nm. The dendrimer nanocomposites are fluorescent, and their surface charge, cellular internalization, toxicity, and cell labeling capabilities are determined by the surface functionalities of dendrimer templates. The {(Ag0)25-PAMAM_E5.NH2} and {(Ag0)25-PAMAM_E5.NSAH} nanocomposites exhibit potential application as cell biomarkers.