Zhao Zichen, Chen Shan, Ho John Kin Lim, Chieng Ching-Chang, Chen Ting-Hsuan
Department of Mechanical and Biomedical Engineering, City University of Hong Kong, Hong Kong Special Administrative Region, China.
Analyst. 2015 Dec 7;140(23):7876-85. doi: 10.1039/c5an01123j.
Visual detection of nucleic acid biomarkers is a simple and convenient approach to point-of-care applications. However, issues of sensitivity and the handling of complex bio-fluids have posed challenges. Here we report on a visual method detecting nucleic acids using Mie scattering of polystyrene microparticles and the magnetophoretic effect. Magnetic microparticles (MMPs) and polystyrene microparticles (PMPs) were surface-functionalised with oligonucleotide probes, which can hybridise with target oligonucleotides in juxtaposition and lead to the formation of MMPs-targets-PMPs sandwich structures. Using an externally applied magnetic field, the magnetophoretic effect attracts the sandwich structure to the sidewall, which reduces the suspended PMPs and leads to a change in the light transmission via the Mie scattering. Based on the high extinction coefficient of the Mie scattering (∼3 orders of magnitude greater than that of the commonly used gold nanoparticles), our results showed the limit of detection to be 4 pM using a UV-Vis spectrometer or 10 pM by direct visual inspection. Meanwhile, we also demonstrated that this method is compatible with multiplex assays and detection in complex bio-fluids, such as whole blood or a pool of nucleic acids, without purification in advance. With a simplified operation procedure, low instrumentation requirement, high sensitivity and compatibility with complex bio-fluids, this method provides an ideal solution for visual detection of nucleic acids in resource-limited settings.
核酸生物标志物的视觉检测是一种简单便捷的即时检测应用方法。然而，灵敏度问题以及复杂生物流体的处理带来了挑战。在此，我们报告一种利用聚苯乙烯微球的米氏散射和磁泳效应来视觉检测核酸的方法。磁性微球（MMPs）和聚苯乙烯微球（PMPs）用寡核苷酸探针进行表面功能化，这些探针可与并列的靶寡核苷酸杂交，导致形成MMPs - 靶标 - PMPs夹心结构。通过施加外部磁场，磁泳效应将夹心结构吸引到侧壁，这减少了悬浮的PMPs，并通过米氏散射导致光透射率发生变化。基于米氏散射的高消光系数（比常用的金纳米颗粒大约3个数量级），我们的结果表明，使用紫外 - 可见光谱仪检测限为4 pM，直接目视检查为10 pM。同时，我们还证明了该方法与多重检测兼容，并且可在复杂生物流体（如全血或核酸池）中进行检测，无需预先纯化。该方法操作程序简化，仪器要求低，灵敏度高，并且与复杂生物流体兼容，为资源有限环境下核酸的视觉检测提供了理想的解决方案。
