The COVID-19 pandemic has highlighted the importance and urgent need for rapid and accurate diagnostic tests for COVID-19 detection and screening. The objective of this work was to develop a simple immunosensor for rapid and high sensitivity measurements of SARS-CoV-2 nucleocapsid protein in serum. This assay is based on a unique sensing scheme utilizing dually-labeled magnetic nanobeads for immunomagnetic enrichment and signal amplification. This immunosensor is integrated onto a microfluidic chip, which offers the advantages of minimal sample and reagent consumption, simplified sample handling, and enhanced detection sensitivity. The functionality of this immunosensor was validated by using it to detect SARS-CoV-2 nucleocapsid protein, which could be detected at concentrations as low as 50 pg/mL in whole serum and 10 pg/mL in 5× diluted serum. We also adapted this assay onto a handheld smartphone-based diagnostic device that could detect SARS-CoV-2 nucleocapsid protein at concentrations as low as 230 pg/mL in whole serum and 100 pg/mL in 5× diluted serum. Lastly, we assessed the capability of this immunosensor to diagnose COVID-19 infection by testing clinical serum specimens, which revealed its ability to accurately distinguish PCR-positive COVID-19 patients from healthy, uninfected individuals based on SARS-CoV-2 nucleocapsid protein serum levels. To the best of our knowledge, this work is the first demonstration of rapid (<1 h) SARS-CoV-2 antigen quantification in whole serum samples. The ability to rapidly detect SARS-CoV-2 protein biomarkers with high sensitivity in very small (<50 μL) serum samples makes this platform a promising tool for point-of-care COVID-19 testing.

中文翻译：

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用于快速、高灵敏度测量血清中 SARS-CoV-2 核衣壳蛋白的微流磁免疫传感器

COVID-19 大流行凸显了快速、准确的诊断测试对 COVID-19 检测和筛查的重要性和迫切需要。这项工作的目的是开发一种简单的免疫传感器，用于快速、高灵敏度地测量血清中的 SARS-CoV-2 核衣壳蛋白。该测定基于独特的传感方案，利用双标记磁性纳米珠进行免疫磁性富集和信号放大。该免疫传感器集成到微流控芯片上，具有样品和试剂消耗最少、简化样品处理和增强检测灵敏度的优点。该免疫传感器的功能通过检测 SARS-CoV-2 核衣壳蛋白得到验证，全血清中的浓度可低至 50 pg/mL，5 倍稀释血清中的浓度可低至 10 pg/mL。我们还将此测定方法应用于基于智能手机的手持式诊断设备，该设备可以检测全血清中浓度低至 230 pg/mL 和 5 倍稀释血清中浓度低至 100 pg/mL 的 SARS-CoV-2 核衣壳蛋白。最后，我们通过测试临床血清标本评估了该免疫传感器诊断 COVID-19 感染的能力，结果表明其能够根据 SARS-CoV-2 核衣壳蛋白血清准确区分 PCR 阳性的 COVID-19 患者与健康未感染个体水平。据我们所知，这项工作首次展示了全血清样本中快速（<1 小时）SARS-CoV-2 抗原定量。该平台能够在非常小的（<50 μL）血清样本中以高灵敏度快速检测 SARS-CoV-2 蛋白生物标志物，这使得该平台成为用于即时检测 COVID-19 的有前景的工具。