Mass testing is fundamental to face the pandemic caused by the coronavirus SARS-CoV-2 discovered at the end of 2019. To this aim, it is necessary to establish reliable, fast, and cheap tools to detect viral particles in biological material so to identify the people capable of spreading the infection. We demonstrate that a colorimetric biosensor based on gold nanoparticle (AuNP) interaction induced by SARS-CoV-2 lends itself as an outstanding tool for detecting viral particles in nasal and throat swabs. The extinction spectrum of a colloidal solution of multiple viral-target gold nanoparticles—AuNPs functionalized with antibodies targeting three surface proteins of SARS-CoV-2 (spike, envelope, and membrane)—is red-shifted in few minutes when mixed with a solution containing the viral particle. The optical density of the mixed solution measured at 560 nm was compared to the threshold cycle (C_t) of a real-time PCR (gold standard for detecting the presence of viruses) finding that the colorimetric method is able to detect very low viral load with a detection limit approaching that of the real-time PCR. Since the method is sensitive to the infecting viral particle rather than to its RNA, the achievements reported here open a new perspective not only in the context of the current and possible future pandemics, but also in microbiology, as the biosensor proves itself to be a powerful though simple tool for measuring the viral particle concentration.

中文翻译：

---

快速检测鼻咽拭子中SARS-CoV-2的比色测试

大规模测试对于应对2019年底发现的冠状病毒SARS-CoV-2引起的大流行至关重要。为此，有必要建立可靠，快速且廉价的工具来检测生物材料中的病毒颗粒，以便识别有能力传播感染的人。我们证明比色生物传感器基于由SARS-CoV-2诱导的金纳米颗粒（AuNP）相互作用使其自身成为检测鼻腔和咽拭子中病毒颗粒的出色工具。多个病毒目标金纳米颗粒的胶体溶液的消光光谱（与靶向SARS-CoV-2的三种表面蛋白（尖峰，包膜和膜）的抗体功能化的AuNPs）在与溶液混合后几分钟内发生红移含有病毒颗粒。Ç_吨的实时PCR（黄金标准，用于检测病毒的存在）发现该比色法能够与接近于的实时PCR的检测极限，以检测非常低的病毒载量）。由于该方法对感染的病毒颗粒而非其RNA敏感，因此，本文报道的成就不仅在当前和可能的大流行背景下，而且在微生物学方面都开辟了新的前景，因为生物传感器证明了自己是一种病毒。强大而简单的工具来测量病毒颗粒浓度。