Facile Controlled Preparation of Multifunctional Core-Shell Magnetic Nanoparticles and Their Use in Microfluidic Separation
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Continuous microfluidic technology has proven to be a potential competitor with established batch systems for facilitating chemical synthesis and purification, and more amenable to miniaturization, integration, and automation. Nevertheless, combining synthesis, purification and analysis remains a challenge due to the lack of development in efficient continuous flow purification techniques. An emerging continuous-flow purification technique is magnetophoresis, which utilizes surface-functionalized magnetic particles to selectively capture target molecules through specific binding, followed by manipulating the migration of particles through external magnetic force. This dissertation explores the synthesis of monodisperse core-shell functionalized magnetic nanoparticles composed of a single-core structure, and their application in magnetic manipulation for capture and isolation of targets in the continuous flow. First, single-cored magnetic nanoparticles with surface functionalities were prepared by coating functional triethoxysilanes onto iron oxide nanoparticles. The morphology, size, and colloidal stability of the resulting functionalized magnetic nanoparticles can be predicted and controlled. Second, a microfluidic device was fabricated from poly(dimethylsiloxane)(PDMS), consisting of two major components, a mixer and a separator (a diagram shown below). In the mixer, target molecules were captured by functionalized magnetic nanoparticles in a T-shape microchannel. Then the magnetic bead-target complex is directed into the separator, where the captured target molecules are magnetically steered out of the matrix while passing through a laminar co-flow profile. For proof of concept, we used a mixture of toluidine blue O (TBO) and sodium fluorescein as a model target and nontarget, respectively, and carboxyl functionalized magnetic beads as a receptor, leading to the selective complexation of TBO and magnetic beads via electrostatic binding. The device allowed for complete separation of the target from the nontarget molecules with high separation selectivity and efficiency as well as excellent reliability and flexibility.