Tryptophan-based peptides to synthesize gold and silver nanoparticles: a mechanistic and kinetic study

Synthetic oligopeptides with a tryptophan residue at the C-terminus have been used for the synthesis of gold and silver nanoparticles at pH 11. The tryptophan residue in the peptides is responsible for the reduction of metal ions to the respective metals, possibly through electron transfer. A mechanistic pathway has been proposed to explain the reductive properties of the tryptophan moiety of the peptide based on some spectroscopic techniques, such as UV-visible and fluorescence spectroscopy. This study reveals that some of the peptide molecules are converted to its corresponding ditryptophan, kynurenine form and some cross-linked products, all of which are highly fluorescent species. The resultant peptide-functionalized metal nanoparticles have also been characterized by UV-visible spectroscopy, transmission electron microscopy, and Fourier transform IR spectroscopy and thermogravimatric analysis.     

Photochemical Synthesis and Spectral-Optical Characteristics of ZnO/Cu and ZnO/Ag/Cu Nanoheterostructures

The photoreduction of Cu²⁺ at the surface of ZnO nanoparticles and ZnO/Ag nanostructures was investigated. The spectral characteristics of the obtained ZnO/Cu and ZnO/Ag/Cu composites were studied in relation to the reaction conditions. It was shown that the ZnO/Ag nanoparticles have higher photocatalytic activity in the reduction of Cu²⁺ ions than the individual ZnO particles.     

Miniemulsion Polymerization and the Structure of Polymer and Hybrid Nanoparticles

The miniemulsion process allows the formation of complex polymer nanoparticles and the encapsulation of widely varying materials into a polymer shell (see examples). Functionalization of the nanoparticles can be easily carried out, and polymerization to form polymer nanoparticles can be performed in environmentally friendly solvents, such as water.

     

Loading of Exponentially Grown LBL Films with Silver Nanoparticles and Their Application to Generalized SERS Detection

Feature film : Thin films made by exponential layer‐by‐layer growth display high diffusivity and can be readily infiltrated with inorganic nanoparticles. They can sequestrate molecular systems from solution as a function of the composition of their layers, while providing intense surface‐enhanced Raman scattering (SERS) signals (see picture).

     

An Amperometric Immunosensor Based on Layer‐by‐Layer Assembly of L‐Cysteine and Nanosized Prussian Blue on Gold Electrode for Determination of Human Chorionic Gonadotrophin

A novel amperometric immunosensor based on L ‐cysteine/nanosized Prussian blue bilayer films ({NPB/L ‐cys}₂) and gold nanoparticles (nano‐Au) was fabricated for determination of human chorionic gonadotrophin (HCG). First, L ‐cys and NPB was self‐assembled by layer‐by‐layer (LBL) technology to form {NPB/L ‐cys}₂ bilayer films on the gold electrode. Subsequently, nano‐Au layer was immobilized on the {NPB/L ‐cys}₂ bilayer films by electrodepositing gold chloride tetrahydrate and then anti‐HCG was assembly on the nano‐Au layer. Finally hemoglobin (Hb) was employed to block sites against nonspecific binding. With the electrocatalytic ability of Hb and NPB for the reduction of H₂O₂, the current signal of the antigen‐antibody reaction was amplified and the enhanced sensitivity was achieved. In this study, the assembly process and performance of the immunosensor were characterized by cyclic voltammetry (CV) and the morphology was researched by scanning electron microscopy (SEM). The immunosensor performed a high sensitivity and a wide linear response to HCG in two ranges from 0.5 to 10 mIU/mL and from 10 to 200 mIU/mL with a relatively low detection limit of 0.2 mIU/mL at 3 times the background noise, as well as good stability and long‐term life.     

One‐Step Synthesis of Folic Acid Protected Gold Nanoparticles and Their Receptor‐Mediated Intracellular Uptake

We report here a facile method to obtain folic acid (FA)‐protected gold nanoparticles (Au NPs) by heating an aqueous solution of HAuCl₄/FA in which FA acts as both the reducing and stabilizing agent. The successful formation of FA‐protected Au NPs is demonstrated by UV/Vis spectroscopy, transmission electron microscopy (TEM), selected‐area electron diffraction (SAED), X‐ray photoelectron spectroscopy (XPS), and Fourier transform infrared spectroscopy (FTIR). The intracellular uptake of these nanoparticles is facilitated by HeLa cells overexpressing the folate reporter, which itself is significantly inhibited by free FA in a competitive assay as quantified by inductively coupled plasma mass spectroscopy (ICP‐MS). This simple one‐step approach affords a new perspective for creating functional nanomaterials, and the resulting biocompatible, functional Au NPs may find some prospective applications in various biomedical fields.     

Precipitation of hematite nanoparticles via reverse microemulsion process

Hematite nanoparticles have been successfully synthesized via two processing routes:(i) conventional precipitation route and (ii) reverse microemulsion route.The particle precipitation was carried out in a semibatch reactor.A microemulsion system consisting of water,chloroform,1-butanol and surfactant was loaded with iron nitrates to form iron nanoparticles precipitation.The precipitation was performed in the single-phase microemulsion operating region.Three technical surfactants,with different structure and HLB value are employed.The influence of surfactant characterization on the size of produced iron oxide particle has been studied to gain a deeper understanding of the important controlling mechanisms in the formation of nanoparticles in a microemulsion.Transmission electron microscopy (TEM),surface area,pore volume,average pore diameter,pore size distribution and XRD were used to analyze the size,size distribution,shape and structure of precipitated iron nanoparticles.     

Amperometric hydrogen peroxide biosensor based on the immobilization of heme proteins on gold nanoparticles-bacteria cellulose nanofibers nanocomposite

A novel matrix, gold nanoparticles-bacterial cellulose nanofibers (Au-BC) nanocomposite was developed for enzyme immobilization and biosensor fabrication due to its unique properties such as satisfying biocompatibility, good conductivity and extensive surface area, which were inherited from both gold nanoparticles (AuNPs) and bacterial cellulose nanofibers (BC). Heme proteins such as horseradish peroxidase (HRP), hemoglobin (Hb) and myoglobin (Mb) were successfully immobilized on the surface of Au-BC nanocomposite modified glassy carbon electrode (GCE). The immobilized heme proteins showed electrocatalytic activities to the reduction of H₂O₂ in the presence of the mediator hydroquinone (HQ), which might be due to the fact that heme proteins retained the near-native secondary structures in the Au-BC nanocomposite which was proved by UV-vis and IR spectra. The response of the developed biosensor to H₂O₂ was related to the amount of AuNPs in Au-BC nanocomposite, indicating that the AuNPs in BC network played an important role in the biosensor performance. Under the optimum conditions, the biosensor based on HRP exhibited a fast amperometric response (within 1 s) to H₂O₂, a good linear response over a wide range of concentration from 0.3 μM to 1.00 mM, and a low detection limit of 0.1 μM based on S/N = 3. The high performance of the biosensor made Au-BC nanocomposite superior to other materials as immobilization matrix.     

无机纳米粒子的生物合成

无机纳米粒子的生物合成是指利用自然界中细菌、放线菌和真菌等微生物或一些高等植物在常温、常压下合成无机纳米粒子,不需使用有毒化学原料或不产生有毒副产品。该方法不仅是一种绿色的、环境友好的新型纳米材料合成策略,而且对深入了解生物矿化机理以及从理论上指导先进功能材料的设计和合成具有重要意义,因此近年来受到了化学、材料、生物科学等领域研究者的广泛关注。本文根据纳米粒子组成,分别综述了国内外利用生物体合成金属、硫化物和氧化物等无机纳米粒子的研究进展,重点讨论了生物合成的机理。结果表明:生物合成的无机纳米粒子具有尺寸分布窄、稳定性高、生物相容性好、产率高和成本低等优点; 为了适应高金属离子浓度的外界环境,生物体往往通过吸附、还原或沉淀、累积或排出等一系列生化过程改变金属离子的溶解性和毒性,从而导致无机纳米粒子的形成; 合成无机纳米粒子后,微生物通常仍具有繁殖能力,表明这些微生物可以被用于生产无机纳米粒子的生物工厂。然而,生物合成无机纳米粒子涉及到的生理过程非常复杂,微生物种类繁多,不同种类之间的差异也非常大。因此,在阐释生物合成机理、拓展纳米材料的种类和形貌、纳米粒子的后处理和应用等问题上仍需进一步深入研究。     

原子转移自由基聚合与“Click”反应相结合制备Fe3O4@SiO2-g-PDMAEMA及其性质研究

结合原子转移自由基聚合（ATRP）与点击反应（＂Click＂reaction）,在SiO2包裹的Fe3O4磁性纳米粒子（Fe3O4@SiO2）表面接枝聚[甲基丙烯酸-2-（N,N-二甲氨基）乙酯]（PDMAEMA）,得到了表面接枝PDMAEMA的磁性纳米粒子（Fe3O4@SiO2-g-PDMAEMA）.通过1H NMR...