Poly(acrylic acid)-stabilized colloidal gold nanoparticles: synthesis and properties

Combining the intriguing optical properties of gold nanoparticles with the inherent physical and dynamic properties of polymers can give rise to interesting hybrid nanomaterials. In this study, we report the synthesis of poly(acrylic acid) (PAA)-capped gold nanoparticles. The polyelectrolyte-wrapped gold nanoparticles were fully characterized and studied via a combination of techniques, i.e. UV-vis and infrared spectroscopy, dark field optical microscopy, SEM imaging, dynamic light scattering and zeta potential measurements. Although PAA-capped nanoparticles have been previously reported, this study revealed some interesting aspects of the colloidal stability and morphological change of the polymer coating on the nanoparticle surface in an electrolytic environment, at various pH values and at different temperatures.     

Poly(lactide-co-glycolide) nanoparticles as carriers for norcantharidin

Norcantharidin (NCTD) is one of the new chemotherapy agents that have anti-tumor activity. However, the clinical potential of NCTD is limited by its high systemic toxicity, poor solubility in physiological environment and short half-life. In this paper, NCTD loaded poly(lactide-co-glycolide) (PLGA) nanoparticles for controlled delivery were prepared by using an interfacial deposition method. The resulting particles were characterized for their size, morphology, drug loading capacity, entrapment efficiency and in vitro drug release over an extended period of 12 days. The interfacial deposition technique succeeded in building a spherical, monodisperse nanoparticulate delivery system with high entrapment efficiency. The in vitro release lasts for more than 10 days showed a biphasic profile with an initial burst. The in vitro anti-tumor activity of NCTD-PLGA nanocapsules was assessed using the Human Hepatocellular Carcinoma cells SMMC-7721 by the MTT test. Ascites hepatoma (H-22H) and pulmonary adenocarcinoma (LA795) mice models were used to study the in vivo tumoricidal efficacy of NCTD delivery from the PLGA nanoparticles. The results demonstrate that i.v. or i.p. administration of this controlled release system could be of high clinical significance in cancer chemotherapy.     

Poly(amidoamine)-G5 dendrimers/noble metal gold hybrid nanoparticles prepared by γ-ray irradiation

In the absence of a chemical reductant and other protective reagents, noble metal gold hybrid nanoparticles are successfully prepared by ⁶⁰Co γ-ray irradiation using fifth-generation poly(amidoamine) dendrimer with surface amine-terminated group as polymeric template. The zerovalent gold is of spherical structure and the particle size is on nanometer scale range of 3-12 nm. The size distribution of gold nanoparticles displays multidispersity. The results of FTIR show that interactions between dendrimer template and gold nanoparticle exist in intra-molecule and inter-molecule of fifth-generation poly(amidoamine) dendrimer.     

Synthesis and characterization of amino acid containing Cu(II) chelated nanoparticles for lysozyme adsorption

Immobilized metal ion affinity chromatography (IMAC) is a useful method for adsorption of proteins that have an affinity for transition metal ions. In this study, poly(hydroxyethyl methacrylate-methacryloyl-l-tryptophan) (PHEMATrp) nanoparticles were prepared by surfactant free emulsion polymerization. Then, Cu(II) ions were chelated on the PHEMATrp nanoparticles to be used in lysozyme adsorption studies in batch system. The maximum lysozyme adsorption capacity of the PHEMATrp nanoparticles was found to be 326.9 mg/g polymer at pH 7.0. The nonspecific lysozyme adsorption onto the PHEMA nanoparticles was negligible. In terms of protein desorption, it was observed that adsorbed lysozyme was readily desorbed in medium containing 1.0 M NaCl. The results showed that the metal-chelated PHEMATrp nanoparticles can be considered as a good adsorbent for lysozyme purification.     

Poly(ethylene glycol) decorated poly(methylmethacrylate) nanoparticles for protein adsorption

Poly(ethylene glycol) decorated poly(methyl methacrylate) particles were synthesized by means of emulsion polymerization using poly(ethylene glycol) sorbitan monolaurate (Tween-20) as surfactant. PMMA/PEG particles presented mean diameter (195 ± 15) nm, indicating narrow size distribution. The adsorption behavior of bovine serum albumin (BSA) and concanavalin A (ConA) onto PMMA/PEG particles was investigated by means of spectrophotometry. Adsorption isotherms obtained for BSA onto PMMA/PEG particles fitted well sigmoidal function, which is typical for multilayer adsorption. Con A adsorbed irreversibly onto PMMA/PEG particles. The efficiency of ConA covered particles to induce dengue virus quick agglutination was evaluated.     

熔融缩聚合成聚乳酸-聚乙二醇共聚物及其性能研究

采用羧基封端乳酸预聚物与聚乙二醇熔融缩聚合成了聚乳酸-聚乙二醇共聚物,并用GPC、FTIR、1H-NMR等方法表征了预聚物与共聚物,结果表明,预聚物的羧基封端率高于95%,预聚物的相对分子质量可由投料比(物质的量比)控制.热分析结果表明,共聚物中聚乳酸链段呈无规分布,而聚乙二醇链段能够形成结晶微区.力学性能测试结果表明,共聚物的断裂伸长率达371%,有望在聚乳酸韧性改性方面得到应用.     

Poly(vinylpyrrolidone) coated iron nanoparticles in polar aprotic solvent

Poly(vinylpyrrolidone) (PVP) coated iron nanoparticles which show well-defined core-shell structures have been successfully synthesized in a polar aprotic solvent. In this approach, PVP was employed not as capping agent, but as coating polymer directly applied to the metallic (iron) core nanoparticles. The morphologies, structures, compositions and magnetic properties of the products were investigated by transmission electron microscopy (TEM), X-ray powder diffraction (XRD), energy dispersive X-ray spectroscopy (EDXS), SQUID magnetometry and FTIR spectroscopy.     

聚丙烯酸-聚乳酸接枝共聚物涂膜的制备及性能

采用溶液聚合法合成了生物降解材料聚丙烯酸-聚乳酸接枝共聚物(PAA-g-PLLA),通过红外、核磁和凝胶渗透色谱对其结构进行了表征,测定了涂膜的附着力、黏度和硬度等基本性能。正交实验结果表明最佳的合成工艺条件为:硬软单体的质量比为55∶35,过氧化苯甲酰(BPO)的用量为3%,反应温度为85℃,甲基丙烯酸羟乙酯-聚乳酸大单体(HEMA-PLLA)与软硬单体的质量比为1∶2,单体与溶剂的质量比为2∶2。对比聚丙烯酸涂膜和PAA-g-PLLA涂膜的接触角,以及PLLA降解性能看出,PAA-g-PLLA涂膜具有降低表面能和自抛光的双重特性。     

原位反应挤出制备聚乳酸与聚醚酯嵌段共聚物合金的性能研究

以0.35%(质量分数)的过氧化二异丙苯(DCP)为引发剂和2%(质量分数)的马来酸酐(MAH)为增容剂,通过原位反应挤出的方法制备了聚乳酸(PLLA)/聚醚酯嵌段共聚物(TPEE)合金。利用TG、差示扫描量热(DSC)、SEM等研究了其热性能和相形态,并测试了合金的力学性能和熔体流动速率。结果表明,在引发剂DCP的存在下,MAH的添加使得反应挤出制备的合金中PLLA与TPEE之间产生部分共价键连接而增加了相容性。合金的热稳定性、韧性随TPEE含量的增加而升高,但模量和强度下降。另外,不同TPEE含量的合金的熔体流动速率均高于纯PLLA和TPEE,表明在原位反应挤出过程中PLLA与TPEE均发生了一定程度的降解反应。同时,对合金的流变性能也进行了研究。     

生物降解材料聚乳酸的共聚改性研究进展

概述了生物降解材料聚乳酸的物理机械性能和生物性能,指出对聚乳酸进行改性的必要性及常用方法,其中共聚改性方法是最有效的途径之一.综述了聚乳酸与聚乙醇酸、聚己内酯、聚乙二醇、聚氨基酸等的共聚方法、共聚物的性能及其应用.经共聚改性后聚乳酸的力学性能、亲水性能或反应功能性能可以得到改善,降解周期可实现调控,从而满足在生物医学及环保方面的应用需求.     

Poly(lactide-co-glycolide)-methoxy-poly(ethylene glycol) nanoparticles: drug loading and release properties

In this work, the drug loading and in vitro release properties of PLGA-mPEG nanoparticles were studied. Three methyl-xanthine derivatives differing significantly in aqueous solubility, i.e., caffeine, theophylline, and theobromine, were employed as model drugs. Two different PLGA-mPEG copolymer compositions, namely PLGA(40)mPEG(5) and PLGA(136)mPEG(5), were included in the study. The nanoparticles were prepared by a double emulsion technique. The drug release properties of the nanoparticles in phosphate buffered saline (PBS) and in human plasma were determined. An increase of the drug proportion in the feed led to increased drug loading. The composition of the PLGA-mPEG copolymer (PLGA/mPEG molar ratio) did not appear to affect drug loading and encapsulation. Caffeine exhibited higher loading in the nanoparticles than theobromine and this exhibited a little higher loading than theophylline. Solid-state solubility of the drug in PLGA-mPEG did not affect drug loading. Drug loading and encapsulation in the PLGA-mPEG nanoparticles appeared to be governed by the partition coefficient of the drug between the organic phase and the external aqueous phase employed in nanoparticle preparation. Relatively low loading and encapsulation values were obtained, suggesting that the physical entrapment of drugs in PLGA-mPEG nanoparticles could only be an option in the development of formulations of potent drugs. Only the release of the least water-soluble theobromine was efficiently sustained by its entrapment in the nanoparticles, indicating that the physical entrapment of drugs provides the means for the development of controlled-release PLGA-mPEG nanoparticulate formulations only in the case of drugs with low aqueous solubility.     

Single-walled carbon nanotube growth from highly activated metal nanoparticles

We demonstrate that any metal, even gold, silver, and copper, can act as a catalyst for SWCNT synthesis in chemical vapor deposition (CVD). Metal nanoparticles 3 nm or less in diameter, introduced into CVD ambience immediately after heat treatment at 800-950 degrees C in air, produce SWCNTs. The activation method is effective for copper and various noble metals as well as for iron-family elements. This implies that any metal particle may produce SWCNTs when its size becomes 1-3 nm. In other words, carbon atoms can form SWCNTs in a self-assembling fashion on nanoparticles without the specific functions of iron-family elements.     

不同相对分子质量聚乙二醇增塑聚乳酸共混物的制备与性能

文中探究不同相对分子质量聚乙二醇(PEG)对聚乳酸(PLA)增塑改性的影响。采用转矩流变仪、万能试验机、差示扫描量热分析、动态力学、热重分析、旋转流变仪等测试表征方法对共混材料的增塑效果、力学性能、热行为、流变行为进行分析。实验结果表明,PEG可有效增塑PLA,PEG相对分子质量越低增塑效果越好,可以使PLA的塑化时间从250 s降低到128 s;加入PEG后,共混物的拉伸强度下降,断裂伸长率提高,PEG相对分子质量越低,拉伸强度下降越明显;PEG的加入使PLA的T_g和T_(cc)降低20℃左右,而T_m有所提高,其中低相对分子质量PEG可以更好地促进PLA结晶,但是随着PEG的加入共混体系的热分解温度降低,相对分子质量越低,热分解温度降低越明显;流变实验表明共混体系的复数黏度(η*)、储能模量(G')及损耗模量(G')的变化随PEG相对分子质量的减小下降越明显。     

Poly(ethylene glycol dimethacrylate-n-vinyl imidazole) beads for heavy metal removal

Poly(ethylene glycol dimethacrylate-n-vinyl imidazole) [poly(EGDMA-VIM)] hydrogel (average diameter 150-200 microm) was prepared by copolymerizing ethylene glycol dimethacrylate (EGDMA) with n-vinyl imidazole (VIM). The copolymer hydrogel bead composition was characterized by elemental analysis and found to contain 5 EGDMA monomer units each VIM monomer unit. Poly(EGDMA-VIM) beads had a specific surface area of 59.8 m2/g. Poly(EGDMA-VIM) beads were characterized by swelling studies and scanning electron microscopy (SEM). These poly(EGDMA-VIM) beads with a swelling ratio of 78% were used for the heavy metal removal studies. Chelation capacity of the beads for the selected metal ions, i.e., Cd(II), Hg(II) and Pb(II) were investigated in aqueous media containing different amounts of these ions (10-750 mg/l) and at different pH values (3.0-7.0). Chelation rate was very fast. The maximum chelation capacities of the poly(EGDMA-VIM) beads were 69.4 mg/g for Cd(II), 114.8 mg/g for Pb(II) and 163.5 mg/g for Hg(II). The affinity order on molar basis was observed as follows: Hg(II) > Cd(II) > Pb(II). Chelation behavior of heavy metal ions could be modelled using both the Langmuir and Freundlich isotherms. pH significantly affected the chelation capacity of VIM incorporated beads. Chelation of heavy metal ions from synthetic wastewater was also studied. The chelation capacities are 45.6 mg/g for Cd(II), 74.2 mg/g for Hg(II) and 92.5 mg/g for Pb(II) at 0.5 mmol/l initial metal concentration. Regeneration of the chelating-beads was easily performed with 0.1 M HNO3. These features make poly(EGDMA-VIM) beads potential candidate adsorbent for heavy metal removal.     

Fabrication of ZnO nanorods using metal nanoparticles as growth nuclei

ZnO nanorods were produced by pulsed laser deposition (PLD). Drops of nanoparticle colloid (gold or silver) were placed on silica substrates to form growth nuclei. All nanoparticles were monocrystalline, with well-defined crystal surfaces and a negative electrical charge. The ZnO nanorods were produced in an off-axis PLD configuration at oxygen pressure of 5 Pa. The growth of the nanorods started from the nanoparticles in different directions, as one nanoparticle could become a nucleus for more than one nanorod. The low substrate temperature used indicates the absence of a catalyst during the growth of the nanorods. The diameters of the fabricated 1-D ZnO nanostructures were in the range of 50-120 nm and their length was determined by the deposition time.     

聚乳酸接枝共聚物的研究进展

接枝共聚改性是提高聚乳酸性能的一种常用方法,能够扩展其使用范围。从共聚材料种类及性能的角度,分类介绍了近年来利用纤维素、淀粉、壳聚糖、葡聚糖等天然材料和亲水性、温敏性、聚氨基酸类聚合物等合成材料接枝改性聚乳酸的研究进展,分析了各类接枝改性聚乳酸材料的优缺点和应用,展望了该领域未来的发展方向和产业化应用中应该注意的问题,指出在今后聚乳酸基接枝共聚物材料的推广应用中应该关注产品的成本问题。     

聚L-谷氨酸光交联水凝胶的制备和性能

以侧链接枝聚乙二醇丙烯酸酯(APEG)的聚L-谷氨酸(PLGA)(PLGA-g-APEG)为前驱体,通过紫外光交联制备水凝胶,研究了APEG的接枝率及PLGA-g-APEG前驱体质量浓度对光交联水凝胶力学性能的影响。结果表明,当APEG接枝率为44.7%,PLGA-g-APEG的质量分数为15%时,水凝胶的力学性能最佳,其储能模量为16238.2 Pa,压缩破坏应力为0.16 MPa。通过多次循环压缩测试,证实压缩曲线几近重合,表明水凝胶具有良好的回弹性能。最后通过MTT法和死/活实验证明PLGA-g-APEG前驱体及其光交联水凝胶均具有良好的生物相容性,该聚L-谷氨酸光交联水凝胶在再生医学领域具有潜在的应用价值。