SERS based immunoassays for point-of-care diagnostics are a promising tool to facilitate biomarker detection for early disease diagnosis and disease control. The technique is based on a sandwiched system in which antigen is first captured by a selective plasmonic paper substrate and then labeled by an extrinsic Raman label (ERL), consisting of a 60 nm gold nanoparticle (AuNP) functionalized with a mixed monolayer of detection antibody and 4-nitrobenezenethiol (NBT) as a Raman reporter molecule. Here, we report on the use of AuNP modified filter paper as a novel capture membrane in a vertical flow format. This vertical flow configuration affords reproducible flow of sample and label through the capture substrate to overcome diffusion limited kinetics and significantly reduced assay time. The filter paper was selected due to its affordability and availability, while the embedded AuNPs maximized plasmonic coupling with the ERLs and SERS enhancement. Additionally, the embedded AuNP served as a scaffold to immobilize capture antibody to specifically bind antigen. In this work, a SERS-based rapid vertical flow (SERS-RVF) immunoassay for detection of mouse IgG was developed to establish proof-of-principle. Optimization of assay conditions led to a limit of detection of 3 ng/mL, which is comparable to more traditional formats carried out in multi-well plates, and significantly reduced assay time to less than 2 min. Additionally, IgG was accurately quantified in normal mouse serum to validate the SERS-RVF assay for application to the analysis of biological samples. These results highlight the potential advantages of the SERS-RVF platform for point-of-need testing.

用于现场诊断的基于SERS的免疫测定是一种有前途的工具，可促进生物标记物的检测，以进行早期疾病诊断和疾病控制。该技术基于一种夹心系统，在该系统中，抗原首先被选择性的等离子体纸底物捕获，然后被外在拉曼标记（ERL）标记，该拉曼标记由60 nm金纳米颗粒（AuNP）组成，并通过混合的单层检测抗体功能化和4-硝基苯硫醇（NBT）作为拉曼报告分子。在这里，我们报道了使用AuNP改性滤纸作为垂直流格式的新型捕获膜。这种垂直流动配置提供了可重现的样品和标签流经捕获底物的流程，从而克服了扩散受限的动力学并大大缩短了测定时间。选择滤纸是因为其价格适中和实用，而嵌入的AuNPs通过ERL和SERS增强使等离子体耦合最大化。另外，包埋的AuNP用作支架以固定捕获抗体以特异性结合抗原。在这项工作中，用于检测小鼠IgG的基于SERS的快速垂直流（SERS-RVF）免疫测定技术得以开发，以建立原理验证。分析条件的优化导致检测极限为3 ng / mL，这与在​​多孔板中进行的更传统的分析方法相当，并且将分析时间显着减少了不到2分钟。另外，在正常小鼠血清中准确定量了IgG，以验证SERS-RVF测定法可用于生物样品的分析。