Carl R. Woese Institute for Genomic Biology, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA; Nick Holonyak, Jr. Micro and Nanotechnology Laboratory, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA.
Nick Holonyak, Jr. Micro and Nanotechnology Laboratory, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA; Department of Bioengineering, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA.
Talanta. 2021 Apr 1;225:122004. doi: 10.1016/j.talanta.2020.122004. Epub 2020 Dec 23.
Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), the cause of Coronavirus Disease 2019 (COVID-19), poses extraordinary threats and complex challenges to global public health. Quantitative measurement of SARS-CoV-2 antibody titer plays an important role in understanding the patient-to-patient variability of immune response, assessing the efficacy of vaccines, and identifying donors for blood transfusion therapy. There is an urgent and ever-increasing demand for serological COVID-19 antibody tests that are highly sensitive, quantitative, rapid, simple, minimally invasive, and inexpensive. In this work, we developed a single-step, wash-free immunoassay for rapid and highly sensitive quantitative analysis of serological human IgG against SARS-CoV-2 which requires only a single droplet of serum. By simply incubating 4 μL human serum samples with antibody-functionalized gold nanoparticles, a photonic crystal optical biosensor coated with the recombinant spike protein serves as a sensing platform for the formation of sandwich immunocomplex through specific antigen-antibody interactions, upon which the detected IgG molecules can be counted with digital precision. We demonstrated a single-step 15-min assay capable of detecting as low as 100 pg mL human COVID-19 IgG in serum samples. The calculated limit of detecting (LOD) and limit of quantification (LOQ) is 26.7 ± 7.7 and 32.0 ± 8.9 pg mL, respectively. This work represents the first utilization of the Activate Capture + Digital Counting (AC + DC)-based immunoassay for rapid and quantitative analysis of serological COVID-19 antibody, demonstrating a route toward point-of-care testing, using a portable detection instrument. On the basis of the sandwich immunoassay principle, the biosensing platform can be extended for the multiplexed detection of antigens, additional IgGs, cytokines, and other protein biomarkers.
严重急性呼吸综合征冠状病毒 2（SARS-CoV-2）是 2019 年冠状病毒病（COVID-19）的病原体，对全球公共卫生构成了非同寻常的威胁和复杂挑战。定量测量 SARS-CoV-2 抗体滴度对于了解患者免疫反应的个体差异、评估疫苗的疗效以及确定输血治疗的供体具有重要意义。目前迫切需要灵敏、定量、快速、简单、微创和廉价的血清学 COVID-19 抗体检测。在这项工作中，我们开发了一种一步法、无洗涤的免疫测定法，用于快速和高度灵敏地定量分析针对 SARS-CoV-2 的血清 IgG，该方法仅需要一滴血清。只需将 4μL 人血清样本与抗体功能化的金纳米颗粒孵育，包被重组刺突蛋白的光子晶体光学生物传感器就可作为传感平台，通过特异性抗原-抗体相互作用形成三明治免疫复合物，然后可以用数字精度计数检测到的 IgG 分子。我们证明了一种一步法 15 分钟的测定法，能够检测低至 100pgmL 的血清样本中的人 COVID-19 IgG。计算出的检测限（LOD）和定量限（LOQ）分别为 26.7±7.7 和 32.0±8.9pgmL。这项工作首次利用基于激活捕获+数字计数（AC+DC）的免疫测定法快速定量分析血清 COVID-19 抗体，为使用便携式检测仪器实现即时检测铺平了道路。基于三明治免疫测定法的原理，该生物传感平台可扩展用于同时检测抗原、其他 IgG、细胞因子和其他蛋白质生物标志物。
