Structural design and preparation of high-performance QD-encoded polymer beads for suspension arrays

Abstract

Fluorescence-encoded polymer bead-based suspension arrays are widely used in biomolecular screening and diagnostic applications. The interior structure of polymer beads, especially the pore size, plays an important role in the preparation of fluorescent beads with a large encoding capacity and stability. Here, highly cross-linked carboxylated poly(styrene-co-ethylene glycol dimethacrylate-co-methacrylic acid) beads (PSEMBs) with optimum pore sizes were designed, fabricated, and further employed in the preparation of high-performance QD-encoded microbeads via a gradual solvent evaporation method. The PSEMBs and QD-encoded PSEMBs were characterized by scanning electron microscopy (SEM), laser scanning confocal microscopy, and spectrofluorometry. The SEM images and flow cytometry results of PSEMBs demonstrate the good sphericity and uniform particle size distribution. Confocal microscope images illustrate that highly uniform, bright fluorescent beads are obtained and the quantum dots (QDs) have filtrated into the entire microspheres, with the required pore size achieved by adjusting the content of porogen. Furthermore, QD-encoded PSEMBs were found to be photostable without leakage of QDs, and to retain their bright fluorescence for at least 20 days. Immunoassay performances for human IgG detections indicate that carboxyl groups on the fluorescent microsphere surface facilitate efficient attachment of biomacromolecules, and therefore enable high detection sensitivity (0.01 ng mL⁻¹) in sandwich immunoreactions. These results indicate that designed optical encoding microcarriers can be successfully applied to high-throughput and multiplexed biomolecular assays. Moreover, the new porous PSEMBs designed and fabricated in this report can efficiently load other nanoparticles (e.g. magnetic nanoparticles, Au and Ag nanoparticles) for a wide range of applications.