Synthesis of magnetic Fe2O3/Au core/shell nanoparticles for bioseparation and immunoassay based on surface-enhanced Raman spectroscopy.

Magnetic Fe2O3/Au core/shell nanoparticles can be particularly used in biological separation, but the development of an appropriate technique including a production process for higher efficient separation and the subsequent immunoassay for lower level still represent a great challenge. In this article, Fe2O3/Au core/shell nanoparticles with different Au ratios were prepared by reducing HAuCl4 on the surface of gamma-Fe2O3 nanoparticles. Scanning electron microscopy (SEM) images and surface-enhanced Raman spectroscopy (SERS) spectra clearly show that the surfaces of Fe2O3 nanoparticles were covered by Au. SERS signals of pyridine (Py) have been obtained on the Fe2O3/Au nanoparticles, and it has been found that the SERS intensity enhanced with the increase of iterative additions of HAuCl4. The antigens in test solution have been effectively separated by the magnetic Fe2O3/Au core/shell nanoparticles, and subsequent rapid detection was examined by immunoassay analysis based on SERS. The result demonstrates that the magnetic bioseparation program used by this magnetic Fe2O3/Au core/shell nanoparticles could separate almost all of the antigens in test solution. The ease of operation and good separation efficiency of this effective method has shown a potential application for magnetic Fe2O3/Au core/shell nanoparticles in bioseparation.