Microfluidic Synthesis Of QD-encoded Microspheres For Suspension Assay

The rapid development of clinical diagnostics and drug discovery has led to urgent demand for a high throughput assay.This technology needs simuLtaneously detect muLtiple analytes within a small sample.Suspension assays based on barcode particles for tracking analytes become an attractive muLtiplex assay.To successfuLly prepare QD-encoded microspheres poses major challenge for QD-barcodes to commercial application,because it is difficuLt to realize on-demand huge production of barcodes with controlled QD concentration and even-distribution in microbeads.Recently,microfluidic technology has been used as an effective approach to creating barcode microspheres.By simply adjusting the rate and concentration of flow phases,it can excellently control the size,composition and structure of the resuLted beads.In this article,we have developed a microfluidic approach to generate QD-encoded barcodes with controlled sizes and accurate encoding signals and envisage those fluorescent microspheres couLd find wide application in the field of muLtiplexed sensing system.We report a very facile microfluidic strategy for fabricating monodispersed fluorescent quantum dot(QD)-embedded barcodes.The microfluidic device for microbead preparation consists of two parts: a nozzle zone for the breakup of barcode droplets and a snakelike zone used to solidify the microbeads.In this work,nano-sized calcium carbonate(CaCO3)is added to the dispersed phase and used as the crosslinking anent for internal gelationof alginate.Compared to external gelation,the generated microbeads exhibit uniform size distribution(CV=2.7%)that is very important for preparing encoding beads with homogenization of QDs in each bead.By tuning the quantity of the quantum dots with different emission wavelength added to the dispersed phase,single color and muLtiple color barcode particlesare successfuLly prepared in a flow focusing microfluidic devices,which may be usefuL for various applications.In order to get the wide size range of microbeads having a certain mechanical strength.Uniform and size-controllable QD-encoded poly(ethylene glycol)diacrylate(PEGDA)polymer microbeads were produced using a microfluidic device followed by in-situ photopolymerization.The S-shaped and gradually widening channel was designed to allow optimized UV exposure time for photopolymerization and prevent coalescence.The as-obtained PEGDA microbeads exhibited well-defined sphericity and excellent monodispersity with coefficient of variation(CV)below 5 %,and the size varied from 7 ?m to 120 ?m can be selectively controlled by simply adjusting the experimental parameters.The fluorescence performance of the QDs was well reserved without significant peak broadening or distortion.Seven barcode libraries were realized with bright fluorescence and distinguished 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 indicated the applicability of the QD-encoded microbeads for suspension assay.