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A novel approach to the hydrophobic partitioning effect on efficient separation of protein such as BSA was demonstrated by the modification of hydrophobic pockets on the surface of silica-coated magnetic nanoparticles with various alkyl groups at various pH levels. The separation efficiency is strongly reflected and can be attained by controlling the size of the hydrophobic pocket and other factors such as the alkyl chain length, the salt concentration, and the pH levels. Furthermore, the adsorption constant (k(ad)) was calculated for the hydrophobic partitioning interaction between BSA and the hydrophobic pocket size at various pH levels., (Copyright 2010 Elsevier Inc. All rights reserved.)

The work describes a simple and convenient process for highly efficient and direct DNA separation with functionalized silica-coated magnetic nanoparticles. Iron oxide magnetic nanoparticles and silica-coated magnetic nanoparticles were prepared uniformly, and the silica coating thickness could be easily controlled in a range from 10 to 50 nm by changing the concentration of silica precursor (TEOS) including controlled magnetic strength and particle size. A change in the surface modification on the nanoparticles was introduced by aminosilanization to enhance the selective DNA separation resulting from electrostatic interaction. The efficiency of the DNA separation was explored via the function of the amino-group numbers, particle size, the amount of the nanoparticles used, and the concentration of NaCl salt. The DNA adsorption yields were high in terms of the amount of triamino-functionalized nanoparticles used, and the average particle size was 25 nm. The adsorption efficiency of aminofunctionalized nanoparticles was the 4-5 times (80-100%) higher compared to silica-coated nanoparticles only (10-20%). DNA desorption efficiency showed an optimum level of over 0.7 M of the NaCl concentration. To elucidate the agglomeration of nanoparticles after electrostatic DNA binding, the Guinier plots were calculated from small-angle X-ray diffractions in a comparison of the results of energy diffraction TEM and confocal laser scanning microscopy. Additionally, the direct separation of human genomic DNA was achieved from human saliva and whole blood with high efficiency.

Superparamagnetic Fe(3)O(4)@SiO(2) core-shell nanoparticles (ca. 30 nm diameter), which are surface-modified with a thiol-specific functional group, exhibit superb capturing efficiency toward cysteinyl peptides without contamination from nonspecifically interacting peptides, as clearly evidenced through LC/MS/MS analysis.

Abstract: This work describes the development of high efficiency protein separation with functionalized organosilanes on the surface of silica coated magnetic nanoparticles. The magnetic nanoparticles were synthesized with average particle size of 9 nm and silica coated magnetic nanoparticles were obtained by controlling the coating thicknesses on magnetic nanoparticles. The silica coating thickness could be uniformly sized with a diameter of 10–40 nm by a sol–gel approach. The surface modification was performed with four kinds of functionalized organosilanes such as carboxyl, aldehyde, amine, and thiol groups. The protein separation work with organosilane assembled silica coated magnetic nanoparticles was achieved for model proteins such as bovine serum albumin (BSA) and lysozyme (LSZ) at different pH conditions. Among the various functionalities, the thiol group showed good separation efficiency due to the change of electrostatic interactions and protein conformational structure. The adsorption efficiency of BSA and LSZ was up to 74% and 90% corresponding pH 4.65 and pH 11. [Copyright &y& Elsevier]

Abstract: This work described the development of high throughput human DNA purification process with the amino-functionalized silica coated magnetic nanoparticles. The magnetic nanoparticles were synthesized with average particle size of 9 nm and silica-coated magnetic nanoparticles were obtained by controlling the coating thicknesses on magnetic nanoparticles. The silica coating thickness could be uniform-sized in the diameter of 10–40 nm by a sol–gel approach. The surface modification was performed with amino-functionalized organic silanes on silica coated magnetic nanoparticles. The spectroscopic measurements such as a FT-IR (ATR-method) and Vibrational Sample Magnetometer (VSM) were used to characterize the chemical structures and magnetic strengths. To elucidate the relationship among the surface area, pore size distribution and reactivity of the materials, XRD, TEM, BET and Zeta potential were used. The use of functionalized self-assembled magnetic nanoparticles for human DNA separation process gives a lot of advantages rather than the conventional silica based process. [Copyright &y& Elsevier]

An enzyme–magnetic nanoparticle conjugate is prepared viaconjugation of Ni2+ions onto the surface of magnetic nanoparticles to interact with a six histidine-tagged enzyme. The catalytic properties and enzyme rigidification of the conjugates are more stable at high concentrations of aromatic hydrocarbons. [ABSTRACT FROM AUTHOR]

Abstract: Highly ordered mesoporous silica nanoparticles with tunable morphology and pore-size are prepared by the use of a transition metal-chelating surfactant micelle complex using Co2+, Ni2+, Cu2+, and Zn2+ ions. These metal ions formed a metal-P123 micelle complex in an aqueous solution, while the metal ions are chelated to the hydrophilic domain such as the poly(ethylene oxide) group of a P123 surfactant. The different complexation abilities of the utilized transition metal ions play an important role in determining the formation of nano-sized ordered MSNs due to the different stabilization constant of the metal-P123 complex. Consequently, from a particle length of 1700nm in the original mesoporous silica materials, the particle length of ordered MSNs through the metal-chelating P123 micelle templates can be reduced to a range of 180–800nm. Furthermore, the variation of pore size shows a slight change from 8.8 to 6.6nm. In particular, the Cu2+-chelated MSNs show only decreased particle size to 180nm. The stability constants for the metal-P123 complex are calculated on the basis of molar conductance measurements in order to elucidate the formation mechanism of MSNs by the metal-chelating P123 complex templates. In addition, solid-state 29Si, 13C-NMR and ICP-OES measurements are used for quantitative characterization reveal that the utilized metal ions affect only the formation of a metal-P123 complex in a micelle as a template. [Copyright &y& Elsevier]

Abstract: This paper describes a method for the effective and self-oriented immobilization of antibodies on magnetic silica-nanoparticles using a multimeric protein G. Cysteine-tagged recombinant dimers and trimers of protein G were produced in Escherichia coli BL21 by repeated linking of protein G monomers with a flexible (GGGGS)3 linker. Amino-functionalized silica-coated magnetic nanoparticles (SiO2-MNPs, Fe3O4@SiO2) were prepared and coupled to the protein G multimers, giving the final magnetic immunosensor. The optimal conditions for the reaction between the protein Gs and the SiO2-MNPs was a time of 60min and a concentration of 100μg/mL, resulting in coupling efficiencies of 77%, 67% and 55% for the monomeric, dimeric and trimeric protein Gs, respectively. Subsequently, anti-hepatitis B surface antigen (HBsAg) was immobilized onto protein G-coupled SiO2-MNPs. The quantitative efficiency of antibody immobilization found the trimeric protein G to be the best, followed by the dimeric and monomeric proteins, which differs from the coupling efficiencies. Using all three protein constructs in an HBsAg fluoroimmunoassay, the lowest detectable concentrations were 500, 250 and 50ng/mL for the monomeric, dimeric and trimeric protein G-coupled SiO2-MNPs, respectively. Therefore, multimeric protein Gs, particularly the trimeric form, can be employed to improve antibody immobilization and, ultimately, enhance the sensitivity of immunoassays. In addition, the multimeric protein Gs devised in this study can be utilized in other immunosensors to bind the antibodies at a high efficiency and in the proper orientation. [Copyright &y& Elsevier]

Abstract: A solution containing ssDNA was detected by using colloidal gold nanoparticles upon a color change of solution. First of all, we prepared colloidal gold nanoparticles with a size of less than 20nm by means of citrate reduction of HAuCl4. Since colloidal gold nanoparticles modified with citrate anions have a negative charge, they are very well dispersed in the solution due to the negative charge repulsion, showing red color. If the electrostatic repulsion is screened by additives such as NaCl, the nanoparticles start to aggregate, leading to a color alteration. We found that the color alteration is retarded when the solution contains ssDNA, which plays a role in preventing the nanoparticles from aggregation. This allows the determination of whether or not ssDNA is present in a solution. However, the color alteration is not retarded when the solution contains dsDNA. [Copyright &y& Elsevier]