Interdepartmental Program in Biomolecular Science and Engineering, University of California, Santa Barbara, California 93106, United States.
ACS Nano. 2013 Aug 27;7(8):7157-64. doi: 10.1021/nn402563f. Epub 2013 Jul 19.
We present a microfluidic device that detects trace concentrations of drugs of abuse in saliva within minutes using surface-enhanced Raman spectroscopy (SERS). Its operation is demonstrated using methamphetamine. The detection scheme exploits concentration gradients of chemicals, fostered by the laminar flow in the device, to control the interactions between the analyte, silver nanoparticles (Ag-NPs), and a salt. Also, since all species interact while advecting downstream, the relevant reaction coordinates occur with respect to the position in the channel. The system was designed to allow the analyte first to diffuse into the side stream containing the Ag-NPs, on which it is allowed to adsorb, before salt ions are introduced, causing the Ag-NPs to aggregate, and so creating species with strong SERS signal. The device allows partial separation via diffusion of the analyte from the complex mixture. Also, the reproducible salt-induced NP aggregation decouples the aggregation reaction (necessary for strong SERS) from the analyte concentration or charge. This method enables the creation of a region where detection of the analyte of interest via SERS is optimal, and dramatically extends the classes of molecules and quality of signals that can be measured using SERS, compared to bulk solution methods. The spatial distribution of the SERS signals was used to map the degree of nanoparticle aggregation and species diffusion in the channel, which, together with numerical simulations, was used to describe the kinetics of the colloid aggregation reaction, and to determine the optimal location in the channel for SERS interrogation.
我们提出了一种微流控装置，它使用表面增强拉曼光谱（SERS）在数分钟内检测唾液中的痕量滥用药物。其操作使用冰毒进行了演示。该检测方案利用了化学物质的浓度梯度，这些梯度是由设备中的层流产生的，以控制分析物、银纳米颗粒（Ag-NPs）和盐之间的相互作用。此外，由于所有物种在向下游输送时都相互作用，因此相关的反应坐标相对于通道中的位置发生。该系统的设计允许分析物首先扩散到含有 Ag-NPs 的侧流中，在那里它被允许吸附，然后再引入盐离子，导致 Ag-NPs 聚集，从而产生具有强 SERS 信号的物质。该装置允许通过分析物从复杂混合物中的扩散进行部分分离。此外，可重复的盐诱导的 NP 聚集将聚集反应（强 SERS 所需）与分析物浓度或电荷解耦。与体相溶液方法相比，这种方法能够创建一个区域，通过 SERS 对感兴趣的分析物进行最佳检测，并极大地扩展了可以使用 SERS 测量的分子种类和信号质量。SERS 信号的空间分布用于绘制通道中纳米颗粒聚集和物质扩散的程度，这与数值模拟一起用于描述胶体聚集反应的动力学，并确定通道中用于 SERS 询问的最佳位置。
