Synthesis of new type of Au-magnetic nanocomposite and application for protein separation thereof
© Song et al.; licensee Springer. 2012
Received: 17 May 2012
Accepted: 3 July 2012
Published: 3 July 2012
We present a different strategy for synthesizing the Au-γ-Fe2O3 bifunctional nanoparticle by using a larger (50 nm) Au nanoparticle as the core surrounded by smaller (10 nm) γ-Fe2O3 nanoparticles. The synthesis of the composite nanoparticles is quite facile based on a simple redox process whereby Fe2+ is used to reduce Au3+. The morphology and composition of the product is measured by transmission electron microscopy, X-ray powder diffraction and UV–vis spectroscopy. We demonstrate the utility of these as-prepared Au-γ-Fe2O3 nanoparticles by showing they can be used to separate proteins in solution. For example, bovine serum is efficiently removed from an aqueous solution with the simple addition of the NPs and application of a small magnet. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis is performed to evaluate the fidelity and efficiency of the protein separation procedure.
Nanoparticles (NPs) containing two completely different elemental compositions (i.e., bifunctional nanomaterials) enable a single particle to have physical properties vastly superior to those made solely from the individual elements. Due to their increased versatility, such bifunctional nanomaterials have enhanced potential for the development of new applications in many different areas, especially in biotechnology. For example, a single composite nanoparticle derived from gold (Au) and iron oxide nanoparticle subunits is quite versatile, having excellent surface chemistry, superior optical characteristics of gold and superparamagnetic properties of iron oxide [1–7].
Commonly, such Au-maghemite (γ-Fe2O3) bifunctional nanoparticles have a γ-Fe2O3 core, either a solid Au shell or smaller Au nanoparticles surrounding the core [8, 9]. We present a different strategy for synthesizing the Au-γ-Fe2O3 bifunctional nanoparticle by using a larger (50 nm) Au nanoparticle as the core surrounded by smaller (10 nm) γ-Fe2O3 nanoparticles. The synthesis of the composite nanoparticles is quite facile based on an easy redox process whereby Fe2+ was used to reduce Au3+. One advantage of this composition is that the size of the bifunctional nanoparticle is easily tuned by changing the size of the Au nanoparticle core while still maintaining a strong magnetic response since a significant amount of magnetic material composes the single particle.
We demonstrate the utility of these as-prepared Au-γ-Fe2O3 nanoparticles by showing they can be used to separate proteins in solution. For example, bovine serum is efficiently removed from an aqueous solution with the simple addition of the NPs and application of an external magnetic field. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) is performed to evaluate the fidelity and efficiency of the protein separation procedure.
All chemicals were purchased from Sigma-Aldrich Corporation (MO, USA) and used as received without further purification. Deionized water was used throughout. The TEM images were taken using a JEOL 2000EX transmission electron microscope (JEOL Ltd., Tokyo, Japan) at an accelerating voltage of 200 kv. The UV–vis spectra were taken by Lambda 950 UV–vis spectrometer (PerkinElmer, MA, USA).
Results and discussion
To test these materials for protein separation, bovine serum solution was added in the sample. Then, by using external magnetic separation, the sample was divided to liquid and paste which was redispersed in water for SDS-PAGE electrophoresis gel.
Sodium dodecyl sulfate- polyacrylamide gel electrophoresis was then applied according to the literature . As shown in Figure 6, compared to the marker in lane 0, the original mixture solution (as shown in lane 1) contained proteins of various molecular sizes. After magnetic separation, those proteins were removed from the solution (lane 2). For the solid sample after separation, the proteins were obtained again (lane 3), so the protein was effectively separated and collected.
We reported the synthesis of gold-maghemite nanoparticles and their use in separating proteins. The as-prepared nanocomposites combined the merits of both gold and magnetic nanoparticles, and were produced by a very easy method. Furthermore, this experiment has also suggested a new way to synthesize various bifunctional or multifunctional composite nanomaterials through simple redox process.
YS is a an MD and a pharmacist-in-charge. YS's research areas are pharmaceutics and Chinese medicine pharmacology, and is affiliated to Department of Pharmacy, Third Affiliated Hospital of Southern Medical University, Guangzhou, 510630, China. LT is an MD whose research is on pharmaceutics and Chinese medicine pharmacology, and is affiliated to the Research Division of Pharmacology, Guiyang Medical College, Guiyang, 550004, China. XS is also an MD and PI whose research areas are on nanotechnology, pharmaceutics and Chinese medicine pharmacology. XS is affiliated to the Research Division of Pharmacology, Guiyang Medical College, Guiyang, 550004, China.
This research is funded by the National Natural Science Foundation of China (grant no.: 30701024), Guizhou Province Special Assistant to Funding High-Level Talent (TZJF-2006-13), Guizhou International Technology Cooperation Fund (grant no.: G  700115); and the Provincial Key Technologies R&D Program of Guizhou (grant no.: S  3010).
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