Low-cost, instrument-free colorimetric tests were developed to detect SARS-CoV-2 using plasmonic biosensors with Au nanoparticles functionalized with polyclonal antibodies (f-AuNPs). Intense color changes were noted with the naked eye owing to plasmon coupling when f-AuNPs form clusters on the virus, with high sensitivity and a detection limit of 0.28 PFU mL^–1 (PFU stands for plaque-forming units) in human saliva. Plasmon coupling was corroborated with computer simulations using the finite-difference time-domain (FDTD) method. The strategies based on preparing plasmonic biosensors with f-AuNPs are robust to permit SARS-CoV-2 detection via dynamic light scattering and UV–vis spectroscopy without interference from other viruses, such as influenza and dengue viruses. The diagnosis was made with a smartphone app after processing the images collected from the smartphone camera, measuring the concentration of SARS-CoV-2. Both image processing and machine learning algorithms were found to provide COVID-19 diagnosis with 100% accuracy for saliva samples. In subsidiary experiments, we observed that the biosensor could be used to detect the virus in river waters without pretreatment. With fast responses and requiring small sample amounts (only 20 μL), these colorimetric tests can be deployed in any location within the point-of-care diagnosis paradigm for epidemiological control.

中文翻译：

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使用等离子生物传感器和智能手机对 SARS-CoV-2 进行比色检测

开发了低成本、无需仪器的比色测试，使用具有多克隆抗体 (f-AuNP) 功能化的金纳米粒子的等离子体生物传感器来检测 SARS-CoV-2。当 f-AuNP 在病毒上形成簇时，由于等离激元耦合，用肉眼即可观察到强烈的颜色变化，灵敏度高，在人类唾液中的检测限为 0.28 PFU mL –1（PFU 代表空斑形成单位^）。使用时域有限差分（FDTD）方法通过计算机模拟证实了等离子体激元耦合。基于用 f-AuNP 制备等离子体生物传感器的策略非常强大，可以通过动态光散射和紫外可见光谱检测 SARS-CoV-2，而不受其他病毒（例如流感病毒和登革热病毒）的干扰。诊断是通过智能手机应用程序处理从智能手机摄像头收集的图像并测量 SARS-CoV-2 的浓度后做出的。研究发现，图像处理和机器学习算法都可以对唾液样本提供 100% 准确度的 COVID-19 诊断。在附属实验中，我们观察到生物传感器无需预处理即可用于检测河水中的病毒。这些比色测试响应速度快，样品量小（仅 20 μL），可以部署在现场诊断范式内的任何位置，以进行流行病学控制。