Microfluidic SERS chip has become increasingly attractive in sensitive chemical and biomolecular analysis. However, microfluidic SERS chip is substantially limited when detecting weakly adsorbed molecules in fluids, let alone achieving quantitative analysis that is vital for biochemical applications. Herein, a microfluidic SERS chip that can achieve quantitative analysis of weak affinity molecules is developed. By “direct-laser-writing”, silver aggregates inherently modified with citrate are facilely fabricated in microfluidic channel. We demonstrate that the surficial citrate can not only “detain” analytes on plasmonic surface by multi-hydrogen bonding, but also serve as a stable internal-standard, which well solves the two challenges. It shows that the relative standard deviation of melamine SERS intensity at 701 cm can be effectively reduced from about 20% to less than 10% by normalization using the citrate band at 1370 cm. Quantification of melamine in aqueous and milk samples down to 10 M are achieved, respectively. And the recoveries are in the range 95%-115%. Moreover, the detection of a kind of hypoglycemic drug (rosiglitazone) is also performed. This microfluidic SERS chip capable of robust quantification of weak affinity molecules would certainly extend the application scenarios of microfluidic SERS, especially for low dose, high efficiency and real time liquid analysis.

中文翻译：

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用于定量检测弱表面亲和力分子的微流控SERS芯片

微流控 SERS 芯片在敏感的化学和生物分子分析中变得越来越有吸引力。然而，微流控SERS芯片在检测流体中弱吸附分子时受到很大限制，更不用说实现对生化应用至关重要的定量分析了。在此，开发了一种可以实现弱亲和力分子定量分析的微流控SERS芯片。通过“直接激光写入”，可以在微流体通道中轻松制造用柠檬酸盐固有修饰的银聚集体。我们证明，表面柠檬酸盐不仅可以通过多重氢键将分析物“滞留”在等离子体表面，而且可以作为稳定的内标，很好地解决了这两个挑战。结果表明，通过使用 1370 cm 处的柠檬酸盐带进行归一化，可以将 701 cm 处三聚氰胺 SERS 强度的相对标准偏差从约 20% 有效降低至小于 10%。水样和牛奶样品中三聚氰胺的定量分别低至 10 M。回收率在 95%-115% 范围内。此外，还进行了一种降糖药物（罗格列酮）的检测。这种能够对弱亲和力分子进行稳健定量的微流控SERS芯片必将扩展微流控SERS的应用场景，特别是在低剂量、高效率和实时液体分析方面。