Microfluidic synthesis of QD-encoded PEGDA microspheres for suspension assay

Uniform and size-controllable QD-encoded poly(ethylene glycol) diacrylate (PEGDA) microbeads were produced using a microfluidic device followed by in situ photopolymerization. An S-shaped and gradually widening channel was designed to allow optimized UV exposure for photopolymerization and to prevent coalescence. The as-obtained PEGDA microbeads exhibited well-defined sphericity and excellent monodispersity with a coefficient of variation (CV) below 5%. The size varied from 7 μm to 120 μm and can be selectively achieved by simply adjusting the experimental parameters. The fluorescence performance of the QDs was well preserved without significant peak broadening or distortion. Seven barcode libraries were realized with bright fluorescence and distinguishing coding signals which could be conveniently decoded by a flow cytometer. Furthermore, a very facile strategy to conjugate biomolecules on the bead surfaces was developed using polydopamine (PDA). A sandwich immunoassay of rabbit IgG was performed and the applicability of the QD-encoded microbeads for suspension assay was demonstrated.