Rapid and sensitive detection of cholera toxin using gold nanoparticle-based simple colorimetric and dynamic light scattering assay

Herein, a rapid and simple gold nanoparticle based colorimetric and dynamic light scattering (DLS) assay for the sensitive detection of cholera toxin has been developed. The developed assay is based on the distance dependent properties of gold nanoparticles which cause aggregation of antibody-conjugated gold nanoparticles in the presence of cholera toxin resulting discernible color change. This aggregation induced color change caused a red shift in the plasmon band of nanoparticles which was measured by UV–Vis spectroscopy. In addition, we employed DLS assay to monitor the extent of aggregation in the presence of different concentration of cholera toxin. Our assay can visually detect as low as 10 nM of cholera toxin which is lower than the previously reported colorimetric methods. The reported assay is very fast and showed an excellent specificity against other diarrhetic toxins. Moreover, we have demonstrated the feasibility of our method for cholera toxin detection in local lake water.     

Reusable sensor based on functionalized carbon dots for the detection of silver nanoparticles in cosmetics via inner filter effect

We report a low cost selective analytical method based on inner filter effect (IFE) for citrate-silver nanoparticle (cit-AgNP) detection, in which fluorescent amine-derivatized carbon dots (a-CDs) act as the donor and aggregated cit-AgNPs as the energy receptor. Carbon dots (CDs) were chemically modified with ethylenediamine (EDA) moieties via amidic linkage displaying an emission band at 440 nm. The presence of cit-AgNPs produces a remarkably quenching of a-CD fluorescence via IFE, since the free amine groups at CD surface induce the aggregation of cit-AgNPs accompany by a red-shifting of their characteristic plasmon absorption wavelength, which resulted in “turn-on” of the IFE-decreased in CD fluorescence. The proposed method, which involves the use of chelating agents for removal of metal ions interferences, exhibits a good linear correlation for detection of cit-AgNPs from 1.23 × 10⁻⁵ to 6.19 × 10⁻⁵ mol L⁻¹, with limits of detection (LOD) and quantification (LOQ) of 5.17 × 10⁻⁶ and 1.72 × 10⁻⁵ mol L^−1, respectively. This method demonstrates to be efficient and selective for the determination of cit-AgNPs in complex matrices such as cosmetic creams and reveals many advantages such as low cost, reusability, high sensitivity and non time-consuming compared with other traditional methods.     

纳米Ag@SiO2核壳结构的表面等离子体共振效应对铕配合物的荧光增强作用

分别制备了二氧化硅壳层厚度为10、25和80 nm的三种Ag@SiO₂纳米粒子, 合成了铕与不同比例苯甲酸根(BA)的配合物、铕与1, 10-邻菲罗啉(phen)及2, 2''-联吡啶(bpy)的配合物, 并对其进行表征. 表征结果推测配合物的组成为Eu(BA)_nCl_3-n·2H₂O (n=1, 2, 3)、Eu(phen)Cl₃·2H₂O和Eu(bpy)Cl₃·2H₂O. 配合物的荧光光谱显示, 在加入Ag@SiO₂纳米粒子后, 复合物的荧光强度有不同程度的增加, 这可能是由于表面等离子体共振造成的. 不同硅壳厚度的Ag@SiO₂纳米粒子的荧光增强顺序是25 nm>80 nm>10 nm, 这表明二氧化硅核壳厚度约25 nm时有较强的表面等离子体共振效应. 此外, 在这些复合物中, Eu(phen)Cl₃·2H₂O复合物的增强效果是最强的, 而Eu(BA)_nCl_3-n·2H₂O的增强效果是最弱的. 在三个苯甲酸铕配合物中, Eu(BA)₃·2H₂O的增强效果最弱, 其他两个苯甲酸铕复合物增强效果相对较好. 原因可能是含氮配合物(Eu(phen)Cl₃·2H₂O和Eu(bpy)Cl₃·2H₂O)可以和Ag@SiO₂更好地成键, 而苯甲酸铕配合物和Ag@SiO₂纳米粒子的作用相对较弱. Ag@SiO₂纳米粒子有望应用于增强稀土材料的发光.     

Gas‐phase synthesis of Fe‐Bi metastable and dumbbell particles

Fe‐Bi nanoparticles were prepared in the gas‐phase by DC magnetron sputtering and in‐fight annealing. The morphological, structural and compositional properties were investigated by High‐resolution transmission electron microscopy, energy dispersive X‐ray spectroscopy and scanning transmission electron microscopy. High‐resolution microscopy studies show that primary particles produced without in‐flight annealing are spherical with a diameter of about 50 nm. Particles sintered at 773 K acquire a dumbbell structure with Fe‐FeO and Bi sections.     

大麦醇溶蛋白负载白藜芦醇自组装纳米颗粒及其性质研究

采用液-液分散法自组装大麦醇溶蛋白纳米颗粒,重点考察了溶剂(异丙醇)浓度、大麦醇溶蛋白浓度、溶液p H值及离子强度等因素对自组装纳米颗粒粒径和Zeta电位的影响。结果表明:在选择溶剂(异丙醇)浓度为55%,蛋白质浓度为66 mg/m L,分散液p H值为7.0,离子强度为0时,自组装出粒径为(70.0±1.8)nm,Zeta电位9 m V的大麦醇溶蛋白纳米颗粒。在此基础上,进一步制备了白藜芦醇-大麦醇溶蛋白复合纳米颗粒,考察了芯材比对复合纳米颗粒粒径、包封率及载药率的影响,结果表明,当芯材比为1∶5时,自组装复合纳米颗粒的粒径为(135.3±2.5)nm,Zeta电位为(18.91±0.02)m V,包封率为90.4%,载药率为18.8%。扫描电子显微镜结果表明,大麦醇溶蛋白纳米颗粒以及白藜芦醇-大麦醇溶蛋白复合纳米颗粒均为表面光滑的球形颗粒;傅立叶变换红外光谱结果表明,复合纳米颗粒中白藜芦醇与大麦醇溶蛋白之间还存在较强的氢键与静电相互作用。     

Size‐Controlled Construction of Magnetic Nanoparticle Clusters Using DNA‐Binding Zinc Finger Protein

Nanoparticle clusters (NPCs) have attracted significant interest owing to their unique characteristics arising from their collective individual properties. Nonetheless, the construction of NPCs in a structurally well‐defined and size‐controllable manner remains a challenge. Here we demonstrate a strategy to construct size‐controlled NPCs using the DNA‐binding zinc finger (ZnF) protein. Biotinylated ZnF was conjugated to DNA templates with different lengths, followed by incubation with neutravidin‐conjugated nanoparticles. The sequence specificity of ZnF and programmable DNA templates enabled a size‐controlled construction of NPCs, resulting in a homogeneous size distribution. We demonstrated the utility of magnetic NPCs by showing a three‐fold increase in the spin–spin relaxivity in MRI compared with Feridex. Furthermore, folate‐conjugated magnetic NPCs exhibited a specific targeting ability for HeLa cells. The present approach can be applicable to other nanoparticles, finding wide applications in many areas such as disease diagnosis, imaging, and delivery of drugs and genes.     

Investigation of the synergistic effect with chiral D-penicillamine functionalized gold nanoparticle as an additive for enantiomeric separation in capillary electrophoresis

The authors describe a synergistic system for nanoparticle based chiral separation. It is based on the use of a conventional chiral selector hydroxyproyl-β-cyclodextrin and a kind of gold nanoparticle functionalized with D-penicillamine as an additive. This nanomaterial displays a synergistic effect on the efficiency of the enantioseparation of the chiral drugs amlodipine, tropicamide, and ofloxacin. A comparative study on the enantioseparation capability of three separation systems, viz. (a) single hydroxyproyl-β-cyclodextrin system, (b) achiral citrate capped gold nanoparticle/ hydroxyproyl-β-cyclodextrin system, and (c) chiral D-penicillamine functionalized gold nanoparticle/ hydroxyproyl-β-cyclodextrin system was performed. The results show that the D-penicillamine functionalized gold nanoparticle/hydroxyproyl-β-cyclodextrin synergistic system has remarkable superiority. The effects of concentrations of D-penicillamine functionalized gold nanoparticle and hydroxyproyl-β-cyclodextrin, of buffer pH value and concentration, and of applied voltage on the performance of enantioseparation were investigated.     

功能化氮化碳对Pd基甲酸分解制氢催化剂性能的促进作用

负载型Pd基催化剂是最有效的甲酸分解(FAD)制氢催化剂之一,其中氮化碳载体的N含量较高,但是通常一步热解法制备的氮化碳为块状,难以有效分散表面金属纳米粒子(NPs)。 本文通过将尿素前驱体在溶剂化作用后热解得到功能化氮化碳,以此为载体,利用阴离子交换和硼氢化钠直接还原法制备了功能化氮化碳负载的Pd基催化剂(Pd/C₃N₄-F)。 通过扫描电子显微镜(SEM)、透射电子显微镜(TEM)和X射线光电子能谱(XPS)对材料结构进行表征,并通过气体质量流量计测试了催化剂的性能。 Pd/C₃N₄-F具有优异的催化FAD制氢性能,30 ℃下的初始TOF(总转换频率)值和质量比活性分别为1824 h^-1和17.14 mol_H2/(g_Pd·h)。 对产物的气相色谱分析结果也表明没有副产物CO生成,表明催化剂具有优异的选择性。 并且随着温度的升高(30～40 ℃),催化剂性能逐渐提高。     

Radiation stability of powders in mixtures with Al2O3 nanoparticles

A comparative research was conducted to investigate the absorption spectra of barium titanate powders mixtures with aluminum oxide micro- or nanopowders irradiated by electrons. It was established that the addition of aluminum oxide nanopowder enhances the radiation stability of mixtures, which increases with the concentration of nanoparticles. Stability augmentation of mixtures under irradiation is caused by the decrease in the concentration of radiation defects in the anion sublattice of barium titanate.     

单分散“核-卫星”金纳米结构的DNA控制组装：一种新型的纳米分级组装模块

报道了一种单分散“核-卫星”纳米金簇状结构的构造方法,不但可以有效调节卫星粒子的数目,还能实现核与卫星粒子间距离的准确控制. 利用DNA分子高度可控的程序化自组装性能,通过合理控制组装过程中核与卫星粒子表面的DNA修饰密度以及不同金纳米粒子的化学计量比,实现了单分散核-卫星结构的高产率组装,结合使用凝胶电泳这一高效的纳米分离技术实现了目标产物的分离. 该方法保证了卫星粒子表面极低的DNA覆盖率,使其与蛋白分子中的巯基基团具有较强的化学亲和作用,使得金纳米粒子在蛋白功能化石墨烯表面的二维层次化自组装得以实现.