On-demand preparation of quantum dot-encoded microparticles using a droplet microfluidic system

• Published in: Lab on a chip Vol. 11; no. 15; pp. 2561 - 2568
• Main Authors: Ji, Xing-Hu, Cheng, Wei, Guo, Feng, Liu, Wei, Guo, Shi-Shang, He, Zhi-Ke, Zhao, Xing-Zhong
• Format: Journal Article
• Language: English
• Published: England 01.01.2011
• Subjects: Alginates - chemistry; Droplets; Glucuronic Acid - chemistry; Hexuronic Acids - chemistry; Hydrogels; Hydrogels - chemistry; Immunoassay - instrumentation; Immunoassay - methods; Mathematical models; Microfluidic Analytical Techniques - instrumentation; Microfluidic Analytical Techniques - methods; Microfluidics; Microparticles; Multiplexing; Particle Size; Quantum Dots; Sodium alginate; Strategy
• ISSN: 1473-0197; 1473-0189
• DOI: 10.1039/c1lc20150f

Optical barcoding technology based on quantum dot (QD)-encoded microparticles has attracted increasing attention in high-throughput multiplexed biological assays, which is realized by embedding different-sized QDs into polymeric matrixes at precisely controlled ratios. Considering the advantage of droplet-based microfluidics, producing monodisperse particles with precise control over the size, shape and composition, we present a proof-of-concept approach for on-demand preparation of QD-encoded microparticles based on this versatile new strategy. Combining a flow-focusing microchannel with a double T-junction in a microfluidic chip, biocompatible QD-doped microparticles were constructed by shearing sodium alginate solution into microdroplets and on-chip gelating these droplets into a hydrogel matrix to encapsulate CdSe/ZnS QDs. Size-controllable QD-doped hydrogel microparticles were produced under the optimum flow conditions, and their fluorescent properties were investigated. A novel multiplex optical encoding strategy was realized by loading different sized QDs into a single droplet (and thus a hydrogel microparticle) with different concentrations, which was triggered by tuning the flow rates of the sodium alginate solutions entrapped with different-colored QDs. A series of QD-encoded microparticles were controllably, and continuously, produced in a single step with the present approach. Their application in a model immunoassay demonstrated the potential practicability of QD-encoded hydrogel microparticles in multiplexed biomolecular detection. This simple and robust strategy should be further improved and practically used in making barcode microparticles with various polymer matrixes.