Shixing Wang

Visual Detection of Copper(II) by Azide- and Alkyne-Functionalized Gold Nanoparticles Using Click Chemistry†

We report a method for the detection of Cu ions by azideand terminal alkyne-functionalized gold nanoparticles (Au NPs) in aqueous solutions using click chemistry. The catalyst, Cu(I), was conveniently derived from the reduction of Cu(II) in the presence of sodium ascorbate. This method allows the naked eye, without the aid of any advanced instrument, to assay for the presence of Cu ions by the aggregation of Au NPs as a result of the Cu(I)-catalyzed conjugation between the two functional groups. Copper is a transition metal essential for life but also highly toxic to organisms, such as certain algae, fungi and many bacteria and viruses. In recent years, copper has been suspected of causing liver damage in children. The analysis and measurement of copper in environmental and biological samples have become increasingly important. Several methods exist for the detection of Cu ions, for example, those based on organic fluorophores or chromogenic sensors, quantum dots, atomic absorption spectroscopy, inductively coupled plasma mass spectroscopy, absorbance spectro-photometry, peptides and voltammetry. The color changes associated with the aggregation of metal nanoparticles has led to the development of a number of assays for a variety of target species. Colorimetric methods can be convenient and attractive in many applications because they can be easily monitored with the naked eye, without the aid of any advanced instruments. The extinction coefficient of 13 nm-diameter gold nanoparticles is 2.7 4 10m 1 cm , several orders of magnitude more than those of traditional organic chromophores. As a result, colors arising from nanoparticles at nanomolar concentrations can be observed by the naked eye, allowing sensitive detection of small amounts of analytes. Since Cu(I) is used as a catalyst in the cycloaddition reaction between azides and alkynes in click chemistry based on Huisgen6s reaction, the amount of copper needed for its completion is typically small. Therefore, a method that can visualize the progress of the reaction using the aggregation of Au NPs might also be useful for the detection of trace amounts of Cu(II) (by detection of Cu(I)). Because the azide/alkyne functional groups and their conjugation are highly selective and are essentially inert to most biological molecules, oxygen, water, and the majority of common reaction conditions in chemical synthesis, and are tolerant of a wide range of solvents, temperatures, and pH values, we reasoned that an assay based on such chemistry may find myriad uses. Our method for the detection of Cu ions relies on the Cu(I)-catalyzed 1,3-dipolar cycloaddition of alkynes and azides on the surface of functionalized Au NPs, that results in the aggregation of Au NPs (Scheme 1). We synthesized azideand terminal alkyne-functionalized thiols, 1 and 2, and prepared gold NPs coated with these

Growing hyperbranched polyglycerols on magnetic nanoparticles to resist nonspecific adsorption of proteins

Hyperbranched polyglycerols were grown from magnetic nanoparticles (MNPs) via surface-initiated anionic ring-opening polymerization of glycidol. The modified MNPs were characterized by using TEM, XPS, TGA and FTIR. Hyperbranched polyglycerols resist the nonspecific adsorption of proteins on magnetic nanoparticles. The capability of hyperbranched polyglycerols is comparable favorably with the performance of methyloxy poly(ethylene glycol) (a linear mPEG with a molecular weight of 750) in resisting the adsorption of proteins.

Preparation and Characterization of Stimuli-Responsive Magnetic Nanoparticles

In this work, the main attention was focused on the synthesis of stimuli-responsive magnetic nanoparticles (SR-MNPs) and the influence of glutathione concentration on its cleavage efficiency. Magnetic nanoparticles (MNPs) were first modified with activated pyridyldithio. Then, MNPs modified with activated pyridyldithio (MNPs-PDT) were conjugated with 2, 4-diamino-6-mercaptopyrimidine (DMP) to form SR-MNPs via stimuli-responsive disulfide linkage. Fourier transform infrared spectra (FTIR), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS) were used to characterize MNPs-PDT. The disulfide linkage can be cleaved by reduced glutathione (GHS). The concentration of glutathione plays an important role in controlling the cleaved efficiency. The optimum concentration of GHS to release DMP is in the millimolar range. These results had provided an important insight into the design of new MNPs for biomedicine applications, such as drug delivery and bio-separation.

1, 3-dipolar cycloaddition as a general route for functionalization of Fe3O4 nanoparticles

Triazole formation by 1, 3-dipolar cycloaddition reactions has been used to functionalize the surface of Fe(3)O(4) nanoparticles. Fe(3)O(4) particle samples with diameters around 22 nm were synthesized without any additional stabilizer, and were then treated with silane coupling agent to react with propargyl acid. The alkynyl group on the Fe(3)O(4) surface provides better conjugation efficiency with azide derivative molecules, which led to their attachment through the formation of a 1, 2, 3-triazole ring.