Composite Microspheres for Separation of Plasmid DNA Decorated with MNPs through in Situ Growth or Interfacial Immobilization Followed by Silica Coating

Raspberry-like colloidal polymer/magnetite/silica composite microspheres were rationally fabricated based on in situ growth or interfacial immobilization of magnetic nanoparticles (MNPs) onto the polymer matrices and the followed sol–gel coating process. Monodisperse cross-linked poly­(styrene-co-glycidyl methacrylate) microspheres were first prepared by surfactant-free emulsion polymerization, followed by surface modification of carboxyl or amine moieties through thiol-epoxy click chemistry. Then the carboxyl-modified microspheres were in situ decorated with MNPs through solvothermal process or chemical coprecipitation reaction. In parallel, incorporation of MNPs onto polymer matrices was also realized by the interaction of amine-modified polymer microspheres with carboxyl-capped MNPs based on the electrostatic interaction. The two pathways for synthesis of the composite microspheres decorated with MNPs were systematically investigated. Furthermore, the composite microspheres were coated with a thin layer of silica through a sol–gel process. The thus-produced magnetic composite microspheres with desirable magnetization (∼23 emu/g) served as effective supports for high-payload plasmid DNA enrichment (∼17 μg per mg of microspheres), much better than that of the commercial-available sample of SM1–015B (∼12 μg per mg of SM1–015B), shedding lights on the potential advantages of the nanoplatforms for separation of bioactive entities.