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Int. J. Mol. Sci. 2013, 14(3), 6223-6240; doi:10.3390/ijms14036223

Gold-Coated Iron Composite Nanospheres Targeted the Detection of Escherichia coli

1,* , 2,†
6,† and 6,†
1 Department of Analytical Chemistry, Faculty of Pharmacy, Gazi University, Etiler, Ankara 06330, Turkey 2 Science Teaching Programme, Faculty of Education, Gazi University, Besevler, Ankara 06330, Turkey 3 Department of Biology, Faculty of Science, Gazi University, Besevler, Ankara 06330, Turkey 4 Department of Food Engineering, Hacettepe University, Beytepe, Ankara 06530, Turkey 5 Institut des Molécules et Matériaux du Mans IMMM, LUNAM Université, Université du Maine, UMR CNRS 6283 F–72085 Le Mans 9, France 6 Department of Engineering Physics, Faculty of Engineering, Ankara University, Besevler, Ankara 06100, Turkey These authors contributed equally to this work.
* Author to whom correspondence should be addressed.
Received: 28 November 2012 / Revised: 28 February 2013 / Accepted: 28 February 2013 / Published: 18 March 2013
(This article belongs to the Special Issue Magnetic Nanoparticles 2013)
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We report the preparation and characterization of spherical core-shell structured Fe3O4–Au magnetic nanoparticles, modified with two component self-assembled monolayers (SAMs) consisting of 3–mercaptophenylboronic acid (3–MBA) and 1–decanethiol (1–DT). The rapid and room temperature synthesis of magnetic nanoparticles was achieved using the hydroxylamine reduction of HAuCl4 on the surface of ethylenediaminetetraacetic acid (EDTA)-immobilized iron (magnetite Fe3O4) nanoparticles in the presence of an aqueous solution of hexadecyltrimetylammonium bromide (CTAB) as a dispersant. The reduction of gold on the surface of Fe3O4 nanoparticles exhibits a uniform, highly stable, and narrow particle size distribution of Fe3O4–Au nanoparticles with an average diameter of 9 ± 2 nm. The saturation magnetization value for the resulting nanoparticles was found to be 15 emu/g at 298 K. Subsequent surface modification with SAMs against glucoside moieties on the surface of bacteria provided effective magnetic separation. Comparison of the bacteria capturing efficiency, by means of different molecular recognition agents 3–MBA, 1–DT and the mixed monolayer of 3–MBA and 1–DT was presented. The best capturing efficiency of E. coli was achieved with the mixed monolayer of 3–MBA and 1–DT-modified nanoparticles. Molecular specificity and selectivity were also demonstrated by comparing the surface-enhanced Raman scattering (SERS) spectrum of E. coli-nanoparticle conjugates with bacterial growth media.
Keywords: magnetic gold nanoparticle; SERS; immunomagnetic separation; E. coli; surface functionalisation of particles magnetic gold nanoparticle; SERS; immunomagnetic separation; E. coli; surface functionalisation of particles
This is an open access article distributed under the Creative Commons Attribution License (CC BY) which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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Tamer, U.; Cetin, D.; Suludere, Z.; Boyaci, I.H.; Temiz, H.T.; Yegenoglu, H.; Daniel, P.; Dinçer, İ.; Elerman, Y. Gold-Coated Iron Composite Nanospheres Targeted the Detection of Escherichia coli. Int. J. Mol. Sci. 2013, 14, 6223-6240.

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