Facile synthesis of magnetic core-mesoporous shell structured sub-microspheres decorated with NiO nanoparticles for magnetic recyclable separation of proteins

We propose a facile strategy to prepare novel NiO nanoparticle-decorated magnetic core-mesoporous shell structured sub-microspheres (MMMs-NiO) through a facile surfactant-free "in situ silicate growth and NiO formation" approach. The successful deposition of NiO nanoparticles on magnetic cores was verified by XRD, EDS, TEM, SEM and BET characterizations. The NiO units on the obtained nanocomposites were used to selectively enrich and efficiently separate the His-tagged proteins via the specific coordination of histidine of proteins to Ni²⁺ ions. The magnetic core endows the sub-microparticle with high magnetism, enabling facile particle magnetic-separation from the solution under an external magnetic field. The obtained nanocomposites exhibit excellent water dispersity with well-defined size distribution (around 160 nm), mesoporous characteristics, and high magnetization (52.3 emu g^-1). The nanocomposites exhibit excellent selective affinity to His-tag (93%), efficient dissociability by imidazole (86%), and convenient magnetic separability in the separation of His-tagged proteins, as well as from E. coli lysate, even to 5 separation cycles. Therefore, MMMs-NiO is expected to be a satisfactory candidate for practical application in facile and efficient bioseparation in the future. In addition, we expect the synthetic strategy could be extended for the surfactant-free synthesis of other kinds of mesoporous nano/micro-particles.