Microfluidic generation of magnetic-fluorescent Janus microparticles for biomolecular detection.

Fluorescent magnetic multifunctional microparticles were fabricated by a facile droplet microfluidic strategy. Two sodium alginate streams, one doped with Fe3O4 nanoparticles (NPs) and the other with CdSe/ZnS quantum dots, were introduced into a flow-focusing channel as a type of parallel laminar flow to form droplets containing two distinct parts. Then, at the serpentine channel, the Ca(2+) in the oil phase diffused into the droplets, causing the solidification of the droplets. Thus, the Janus microparticles with excellent magnetic/fluorescent properties formed. The flow conditions were optimized and the effects of the flow rates on magnetic/fluorescent compositions were carefully investigated. Luminescent labeling and magnetic separation were simultaneously realized with the newly designed microparticles. Moreover, spatial separation between Fe3O4 NPs and QDs prevented the interference of QDs photoluminescence by the magnetic particles. The as-prepared fluorescent magnetic Janus particles were also successfully employed for DNA assay, which demonstrated the potential of the multifunctional microbeads in biological applications.