Predefinable quantum-dot barcodes

Abstract

Modern biological research requires cost-effective and high-throughput methods to interrogate plenty of biomolecules simultaneously with high efficiency. The suspension multiplexed assays of using barcoded microparticles have obvious advantages over microtiter plates and microarrays for high-throughput screening applications, including less consumption of biological reagents, optimized bioconjugation between the microparticles and biomolecules and higher throughput capability. As a next-generation platform to perform high-throughput screening, the barcoded microparticles have broad applications in drug discovery, gene profiling and diagnostic therapy. Particularly, the barcodes formed by quantum dots (Qdots) attract great attention due to their high coding capacity. However, in the current state of the art, all methods proposed fail to create stable, consistent and repeatable Qdot barcodes for practical usage, rendering these Qdot barcodes non-predefinable in their spectra. This work focuses on the development of predefinable Qdot barcodes in microcapsules which are templated from microfluidic double emulsion droplets. A microfluidic device was developed to form the microcapsules with precise morphology controls, especially, ensuring the Qdot-loaded aqueous cores are fully enclosed in hard polymer shells without leakage. Two types of predefinable barcodes were developed. Firstly, colorimetric barcodes with pre-defined fluorescent profiles were formed by loading Qdots in the aqueous cores of microcapsules, which were stable to ambient fluids due to protection of the hard polymer shells. An image-based decoding method was demonstrated to identify the colorimetric barcodes, in which graphical information of the Qdot-loaded aqueous cores was used to promote the coding capacity. Secondly, easily discernible fluorescent-pattern barcodes with a high coding capacity were formed without using photomasks by loading the quantum dots in different colors in the aqueous cores of multi-component microcapsules. Furthermore, mechanical stability of the microcapsules was examined for processing the assay samples with the barcodes. The methods to tailor the surfaces of barcoded microcapsules with functional groups were also presented. The predefinable Qdot barcodes formed in the microcapsules can be used as a general tool to conduct various screening applications.