Wang Gaobo, Wu Minghui, Chu Lok Ting, Chen Ting-Hsuan
Department of Biomedical Engineering, City University of Hong Kong, Hong Kong Special Administrative Region, 999077, China.
Department of Biomedical Engineering, City University of Hong Kong, Hong Kong Special Administrative Region, 999077, China.
Anal Chim Acta. 2021 May 22;1160:338444. doi: 10.1016/j.aca.2021.338444. Epub 2021 Mar 22.
Cadmium (Cd) is a toxic metal ion widely existing in water, soil and food. Conventional water quality control heavily relies on expensive, bulky and sophisticated instrument such as spectrometry, which is time-consuming and incompatible with on-site, real-time detection. Here, a portable microfluidic device with thermometer-like visual readouts is developed for real-time quantitation of cadmium (II) contamination in drinking water. We use Cd-dependent DNAzyme (Cd16), which is cleaved when Cd is present, creating a single strand DNA which triggers catalytic hairpin assembly (CHA) with two hairpins H1 and H2 as the building blocks. Plenty of H1H2 complex, the product after the Cd-mediated CHA, are generated, which can connect magnetic microparticles (MMPs) and polystyrene microparticles (PMPs), forming "MMPs-H1H2-PMPs" sandwich structure. To provide visual readout to quantitate the particle connection, the particle solution is loaded into a portable microfluidic chip. A magnetic separator first removes MMPs and the connected PMPs, while free PMPs can continue flowing until accumulating into a bar at the particle dam. Shown as a thermometer-like display, the accumulating length is inversely proportional to the concentration of Cd, enabling quantitative detection of Cd by the naked eye. The proposed device exhibits a limit of detection of 11.3 nM of Cd, selectivity >200-fold against other metal ions, high tolerance to the interferents present in drinking water and high recovery rate in tap water. With high analytical performance without any sample preparation step, this portable device is highly promising in real-time monitoring in urban drinking water at sites.
镉（Cd）是一种广泛存在于水、土壤和食物中的有毒金属离子。传统的水质检测严重依赖于昂贵、笨重且复杂的仪器，如光谱仪，这种方法既耗时，又无法实现现场实时检测。在此，我们开发了一种具有温度计式视觉读数的便携式微流控装置，用于实时定量检测饮用水中的镉（II）污染。我们使用了依赖镉的DNA酶（Cd16），当存在镉时它会被切割，产生一条单链DNA，该单链DNA会触发以两个发夹H1和H2为构建模块的催化发夹组装（CHA）。大量镉介导的CHA反应后的产物H1H2复合物生成，其可连接磁性微粒（MMPs）和聚苯乙烯微粒（PMPs），形成“MMPs-H1H2-PMPs”三明治结构。为了提供视觉读数以定量微粒连接情况，将微粒溶液加载到便携式微流控芯片中。磁分离器首先去除MMPs和与之相连的PMPs，而游离的PMPs可继续流动，直至在微粒坝处积聚成条带。呈现为温度计式显示，积聚长度与镉浓度成反比，从而可通过肉眼对镉进行定量检测。所提出的装置对镉的检测限为11.3 nM，对其他金属离子的选择性大于200倍，对饮用水中存在的干扰物具有高耐受性，在自来水中具有高回收率。该便携式装置无需任何样品制备步骤即可具有高分析性能，在城市饮用水现场实时监测方面极具前景。
