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Preparation of Fe3O4@SiO2@Layered Double Hydroxide Core–Shell Microspheres for Magnetic Separation of Proteins

Shao, Mingfei, Ning, Fanyu, Zhao, Jingwen, Wei, Min, Evans, David G., Duan, Xue
Journal of the American Chemical Society 2012 v.134 no.2 pp. 1071-1077
Escherichia coli, adsorption, binding capacity, biosensors, cations, drugs, green fluorescent protein, histidine, magnetic fields, magnetic separation, magnetite, nickel, recombinant proteins, surface area
Three-component microspheres containing an SiO₂-coated Fe₃O₄ magnetite core and a layered double hydroxide (LDH) nanoplatelet shell have been synthesized via an in situ growth method. The resulting Fe₃O₄@SiO₂@NiAl-LDH microspheres display three-dimensional core–shell architecture with flowerlike morphology, large surface area (83 m²/g), and uniform mesochannels (4.3 nm). The Ni²⁺ cations in the NiAl-LDH shell provide docking sites for histidine and the materials exhibit excellent performance in the separation of a histidine (His)-tagged green fluorescent protein, with a binding capacity as high as 239 μg/mg. The microspheres show highly selective adsorption of the His-tagged protein from Escherichia coli lysate, demonstrating their practical applicability. Moreover, the microspheres possess superparamagnetism and high saturation magnetization (36.8 emu/g), which allows them to be easily separated from solution by means of an external magnetic field and subsequently reused. The high stability and selectivity of the Fe₃O₄@SiO₂@NiAl-LDH microspheres for the His-tagged protein were retained over several separation cycles. Therefore, this work provides a promising approach for the design and synthesis of multifunctional LDH microspheres, which can be used for the practical purification of recombinant proteins, as well as having other potential applications in a variety of biomedical fields including drug delivery and biosensors.