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 Fe 3 O 4 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 Fe 3 O 4 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.