| Bead-based suspension array is one of the most promising technologies for high-throughput multiplex detection.Since barcode is the core element of suspension array used to capture and identify target molecules,the preparation of barcodes with high encoding capacity is of great importance.In this study,a novel three-dimensional encoding strategy was developed to fabricate optical barcodes with high encoding capacity in an accurate,controllable and reproducible manner.Firstly,magnetic spheres with diameters of 2.9?m and 6.2?m were used as core substrate to attain different size codes.Secondly,quantum dots were assembled onto the surface of magnetic spheres through modified layer-by-layer assembly proposed here.By the adjustment of QD concentration and the number of QD layers,8 barcodes of small-sized and 10 barcodes of large-sized QD-encoded host particles(QHP)were prepared.Further encapsulation of silica and polyelectrolytes endowed the QHPs with excellent fluorescence stability.As-synthesized host particles were fluorescence stable in different saline solutions and a wide PH range of 5-13.Besides,their fluorescence intensity was almost unchanged during our observation period,such as over 100 days' storage.Thirdly,based on host-guest structure,FITC-doped guest nanoparticles in three different fluorescence intensity levels were mixed at different ratios and covalently conjugated onto the surface of QHPs,thus 5 small-sized and 6 large-sized guest codes were achieved.Finally,by a combinational use of size codes,host codes and guest codes,a three-dimensional barcode library with a capacity of 100 barcodes was established successfully via flow cytometry system.Moreover,five-plexed protein detection showed that the barcodes precisely identified different proteins.In a certain range,the reporter fluorescence intensity was linear to the concentrations of five proteins,demonstrating the great application potential of the barcodes in multiplex detection. |
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