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

TLDR

Fe(3)O(4)@SiO(2)@NiAl-LDH microspheres exhibit a three‑dimensional core‑shell structure with flower‑like morphology, 83 m² g⁻¹ surface area, and 4.3 nm mesochannels. The study aims to develop multifunctional LDH microspheres for efficient purification of recombinant His‑tagged proteins and to explore their potential in drug delivery and biosensing. The microspheres were fabricated by an in‑situ growth method that yields a SiO₂‑coated Fe₃O₄ core surrounded by a NiAl‑LDH nanoplatelet shell. The Ni²⁺ sites in the LDH shell enable high‑capacity (239 µg mg⁻¹) selective binding of His‑tagged GFP, efficient adsorption from E.

Abstract

Three-component microspheres containing an SiO(2)-coated Fe(3)O(4) magnetite core and a layered double hydroxide (LDH) nanoplatelet shell have been synthesized via an in situ growth method. The resulting Fe(3)O(4)@SiO(2)@NiAl-LDH microspheres display three-dimensional core-shell architecture with flowerlike morphology, large surface area (83 m(2)/g), and uniform mesochannels (4.3 nm). The Ni(2+) 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 Fe(3)O(4)@SiO(2)@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.