Multifunctional photonic crystal barcodes from microfluidics

Barcode particles have a demonstrated value for multiplexed high-throughput bioassays. Attempts to develop this technology tend to focus on the generation of featured barcodes both with a large number of identifications to increase the throughput and with novel functions to improve the assays. Here, we report a new class of barcodes that are composed of multiple photonic crystal or magnetic-tagged ethoxylated trimethylolpropane triacrylate (ETPTA) cores and polyethylene glycol (PEG) hydrogel shells. These barcodes are prepared by polymerizing microfluidic multiple double emulsions. As the photonic crystal cores possess distinct reflection peaks, our barcodes allow for a substantial number of coding levels for multiplexing applications. The hydrogel shells surrounding the barcodes enable the creation of three-dimensional scaffolds for immobilizing probes. Moreover, the presence of magnetism in the barcodes confers their controllable movement under magnetic fields, which can be used to significantly increase the sensitivity of the bioassays and to simplify the processing. These features make photonic crystal barcodes ideal for biomedical applications. Biological systems are often studied through the use of assays, in which different experimental parameters are varied systematically. One method uses so-called barcode particles to track different samples. However this approach is complicated by the difficulty of producing barcode systems that allow for a sufficient number of configurations. Zhongze Gu and colleagues from Southeast University in Nanjing, China, have now developed a barcode system based on photonic crystals. These crystals, whose color reflection can be controlled during fabrication, are prepared with the help of a microfluidic system that also enables the simultaneous incorporation of the biomolecules to be probed. The barcodes particles also contain a magnetic tagged component that allows them to be moved in a magnetic field for easier read-out. By combining several types of photonic crystals in one unit, up to 1.28 million marker combinations are possible. Barcodes that composed of multiple colloidal crystal or magnetic-tagged ETPTA cores and PEG hydrogel shells were developed by using microfluidics. As the cores are with distinct reflection peaks, the barcodes allow for substantial number of coding levels for multiplexing. The hydrogel shells surrounding the barcodes enable the creation of three-dimensional scaffolds for immobilizing probes. Moreover, the presence of magnetism in the barcodes confer them controllable movement under magnetic fields, which could significantly increase the sensitivity and simplify the processing of the bioassays.