| Relying on MEMS (Micro Electronic Mechanical System) and having the structural features of the micro-pipeline network, microfluidic device has rapidly developed in the past two decades with the advantages of miniaturization, integration, saving reagents, etc. Its applications involve biological, chemical, medical and other fields. As an important branch of microfluidics, droplet-based microfluidics has the additional advantages of high throughput, high specific surface area, fast heat and mass transfer. It also has extensive applications in chemical synthesis, protein crystallization, single cell analysis, etc. Droplet microreactor used for chemical synthesis has the advantage of rapid mixing, precisely control of the reaction conditions and continuous production of products. And each droplet can be used as an independent microreactor, to avoid contamination between the samples and the sample with the microchannels. Thus droplet microreactor provides a very effective means for the preparation of high-quality nanomaterials. Quantum dot (QD) with high fluorescence quantum yield, good stability, size and element-tunable, make it has great application potentials in biological labeling, biological imaging and biological detection,In this work, the droplets were used as microreactors for controllable continuous synthesis of water-soluble multicolor QDs, and microfluidics were used as experimental platform for realizing virus labeling. The main contents of this paper are illustrated as follows:(1) Continuous synthesis of water soluble Ag2S QDs in droplet microreactor. Syobean oil was used as continuous phase, and the disperse phase was the ethylene glycol solvent contained MPA and silver nitrate which were used as raw materials for synthesis of Ag2S QDs. Droplets were formed in the flowing-focusing structure. The ITO glass slide with designed structure was fabricated with the traditional lithographic method. The temperature of the heated region was controlled by a home-made temperature controlling system. Different-sized Ag2S QDs with near-infrared (NIR)-emitting and visible-emitting were synthesized at different reaction temperatures in droplet microreactors. The reason for the formation of smaller-sized Ag2S nanoparticles at higher temperature was studied.(2) Droplet injection chip was used to continuously regulate the fluorescence emission of CdTe QDs to NIR region. The Cd precursors were injected into the droplets which warping CdTe QDs from the side channel. CdTe QDs continue to grow and the fluorescence emission red-shift from visible region to NIR region. We study the effects of different reaction conditions on the fluorescence emission and particle sizes of QDs. Different emissions of QDs were obtained through a slight change in temperature. Meanwhile, fluorescence spectra of QDs with different emission wavelengthes can be collected online in less than1min. Compared with traditional flasks, the reaction time was greatly shortened in the droplet microreactor. It results from the fast mass and heat transfer, fast mixing and high reaction efficiency in droplet microreactor.(3) Site-specific labeling of baculovirus in an integrated microfluidic device. The envelope protein GP64of baculovirus was fused with the biotin acceptor peptide (AP-tag) and the biotin ligase enzyme (BirA enzyme). The AP-tag could be modified by BirA enzyme to introduce the biotin moiety onto the viral envelope. Site-specific labeling of virus could be achieved through the interaction between biotin and streptavidin. Complex procedures including cell transfection, virus culture and virus labeling were automatically completed in the integrated microfluidic device, which greatly reduced labor intensity and reagent cost. And also the direct contact between viruses and researchers could be eliminated in our "DNA in, Virus out" method, which could greatly improve biosafety of virus-related research. |
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