Department of Mechanical and Biomedical Engineering, City University of Hong Kong, Hong Kong Special Administrative Region.
Lab Chip. 2017 Sep 26;17(19):3240-3245. doi: 10.1039/c7lc00836h.
We demonstrate a microfluidic bead trap capable of forming a dipstick-type bar visible to the naked eye for simple and quantitative detection of oligonucleotides. We use magnetic microparticles (MMPs) and polystyrene microparticles (PMPs) that are connected and form MMPs-targets-PMPs when target oligonucleotides are present, leaving free PMPs with a number inversely proportional to the amount of targets. Using a capillary flow-driven microfluidic circuitry consisting of a magnetic separator to remove the MMPs-targets-PMPs, the free PMPs can be trapped at the narrowing nozzle downstream, forming a visual bar quantifiable based on the length of PMP accumulation. Such a power-free and instrument-free platform enables a limit of detection at 13 fmol (0.65 nM in 20 μl, S/N = 3) of oligonucleotides and is compatible with single-nucleotide polymorphisms and operation in a complex bio-fluid. Moreover, using DNAzyme as the target oligonucleotide that catalyzes a specific hydrolytic cleavage in the presence of lead ions, we demonstrate a model application that detects lead ions with a limit of detection of 12.2 nM (2.5 μg l), providing quantitative and visual detection of lead contamination at resource-limited sites.
我们展示了一种微流控珠阱，能够形成肉眼可见的棒状结构，用于简单、定量地检测寡核苷酸。当存在靶标寡核苷酸时，我们使用连接的磁性微球 (MMPs) 和聚苯乙烯微球 (PMPs)，它们会形成 MMPs-靶标-PMPs，而游离的 PMPs 的数量与靶标数量成反比。使用由磁性分离器组成的毛细管流动驱动微流控电路来去除 MMPs-靶标-PMPs，游离的 PMPs 可以在下游的缩口处被捕获，形成一个可视的棒状结构，其长度可根据 PMP 积累的长度进行定量。这种无电源和无仪器的平台能够实现 13 fmol（20 μl 中 0.65 nM，S/N = 3）的寡核苷酸检测限，并且与单核苷酸多态性兼容，可在复杂生物流体中运行。此外，我们使用 DNA 酶作为靶标寡核苷酸，在铅离子存在下催化特定的水解切割，展示了一种模型应用，能够检测到 12.2 nM（2.5 μg l）的铅离子，从而在资源有限的地点提供铅污染的定量和可视化检测。
