Mechanobiology Institute, National University of Singapore, 117411, Singapore.
Department of Physics, National University of Singapore, 117542, Singapore.
ACS Sens. 2023 Aug 25;8(8):2986-2995. doi: 10.1021/acssensors.3c00393. Epub 2023 Aug 15.
A large portion of the global population has been vaccinated with various vaccines or infected with SARS-CoV-2, the virus that causes COVID-19. The resulting IgG antibodies that target the receptor binding domain (RBD) of SARS-CoV-2 play a vital role in reducing infection rates and severe disease outcomes. Different immune histories result in the production of anti-RBD IgG antibodies with different binding affinities to RBDs of different variants, and the levels of these antibodies decrease over time. Therefore, it is important to have a low-cost, rapid method for quantifying the levels of anti-RBD IgG in decentralized testing for large populations. In this study, we describe a 30 min assay that allows for the quantification of anti-RBD IgG levels in a single drop of finger-prick whole blood. This assay uses force-dependent dissociation of nonspecifically absorbed RBD-coated superparamagnetic microbeads to determine the density of specifically linked microbeads to a protein A-coated transparent surface through anti-RBD IgGs, which can be measured using a simple light microscope and a low-magnification lens. The titer of serially diluted anti-RBD IgGs can be determined without any additional sample processing steps. The limit of detection for this assay is 0.7 ± 0.1 ng/mL referenced to the CR3022 anti-RBD IgG. The limits of the technology and its potential to be further developed to meet the need for point-of-care monitoring of immune protection status are discussed.
全球很大一部分人口已经接种了各种疫苗或感染了导致 COVID-19 的 SARS-CoV-2 病毒。针对 SARS-CoV-2 受体结合域（RBD）的 IgG 抗体在降低感染率和严重疾病结局方面发挥着重要作用。不同的免疫史导致针对不同变体的 RBD 的抗 RBD IgG 抗体具有不同的结合亲和力，并且这些抗体的水平随时间而降低。因此，对于大量人群的分散式检测，拥有一种低成本、快速的定量检测抗 RBD IgG 水平的方法非常重要。在本研究中，我们描述了一种 30 分钟的测定方法，可在一滴手指刺破的全血中定量检测抗 RBD IgG 水平。该测定法使用力依赖性的非特异性吸收的 RBD 包被超顺磁微球的解离来确定通过抗 RBD IgGs 特异性连接的微球到蛋白 A 包被的透明表面的密度，这可以通过简单的显微镜和低倍镜头来测量。通过该测定法，无需任何额外的样品处理步骤即可确定抗 RBD IgG 的系列稀释液的效价。该测定法的检测限为 0.7 ± 0.1 ng/mL，以 CR3022 抗 RBD IgG 为参考。讨论了该技术的局限性及其进一步发展以满足即时护理监测免疫保护状态的需求。
