Porous volumetric capture elements in microfluidic sensors are advantageous compared to planar capture surfaces due to higher reaction site density and decreased diffusion lengths that can reduce detection limits and total assay time. However a mismatch in refractive indices between the capture matrix and fluid within the porous interstices results in scattering of incident, reflected, or emitted light, significantly reducing the signal for optical detection. Here we demonstrate that perfusion of an index-matching fluid within a porous matrix minimizes scattering, thus enhancing optical signal by enabling the entire capture element volume to be probed. Signal enhancement is demonstrated for both fluorescence and absorbance detection, using porous polymer monoliths in a silica capillary and packed beds of glass beads within thermoplastic microchannels, respectively. Fluorescence signal was improved by a factor of 3.5× when measuring emission from a fluorescent compound attached directly to the polymer monolith, and up to 2.6× for a rapid 10 min direct immunoassay. When combining index matching with a silver enhancement step, a detection limit of 0.1 ng/mL human IgG and a 5 log dynamic range was achieved. The demonstrated technique provides a simple method for enhancing optical sensitivity for a wide range of assays, enabling the full benefits of porous detection elements in miniaturized analytical systems to be realized.
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机译:与平面捕获表面相比,微流体传感器中的多孔体积捕获元素具有更高的反应位点密度和减小的扩散长度,可以减少检测限度和总分析时间,因此具有优势。但是,捕获基质与多孔间隙中的流体之间的折射率不匹配会导致入射,反射或发射的光发生散射,从而大大降低了用于光学检测的信号。在这里,我们证明了多孔基质中折射率匹配流体的灌注可最大程度地减少散射,从而通过探测整个捕获元件的体积来增强光信号。分别使用硅胶毛细管中的多孔聚合物整体材料和热塑性微通道内的玻璃珠填充床,证明了荧光和吸光度检测的信号增强。当测量直接附着在聚合物整料上的荧光化合物的发射时,荧光信号提高了3.5倍,而快速10分钟直接免疫测定的荧光信号提高了2.6倍。将指标匹配与银增强步骤结合使用时,检测极限为0.1 ng / mL人IgG和5 log动态范围。所展示的技术提供了一种简单的方法,可以增强针对各种测定的光学灵敏度,从而能够实现小型分析系统中多孔检测元件的全部益处。
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