Label-Free Plasmonic Biosensor for Rapid, Quantitative, and Highly Sensitive COVID-19 Serology: Implementation and Clinical Validation

Abstract

Serological tests are essential for the control and management of COVID-19 pandemic, not only for current and historical diagnostics but especially for surveillance, epidemiological, and acquired immunity studies. Clinical COVID-19 serology is routinely performed by enzymatic or chemiluminescence immunoassays (i.e., ELISA or CLIA), which provide good sensitivities at the expense of relatively long turnaround times and specialized laboratory settings. Rapid serological tests, based on lateral flow assays, have also been developed and widely commercialized, but they suffer from limited reliability due to relatively low sensitivity and specificity. We have developed and validated a direct serological biosensor assay employing proprietary technology based on Surface Plasmon Resonance (SPR). The biosensor offers a rapid -less than 15 min- identification and quantification of SARS-CoV-2 antibodies directly in clinical samples, without the need of any signal amplification. The portable plasmonic biosensor device employs a custom-designed multi-antigen sensor biochip, combining the two main viral antigens (RBD peptide and N protein), for simultaneous detection of human antibodies targeting both antigens. The SPR serology assay reaches detection limits in the low ng mL-1 range employing polyclonal antibodies as standard, which are well below the commonly detected antibody levels in COVID-19 patients. The assay has also been implemented employing the first WHO approved anti-SARS-CoV-2 immunoglobulin standard. We have carried out a clinical validation with COVID-19 positive and negative samples (n=120) that demonstrates the excellent diagnostic sensitivity (99%) and specificity (100%). This positions our biosensor device as an accurate, robust, and easy-to-use diagnostics tool for rapid and reliable COVID-19 serology to be employed both at laboratory and decentralized settings for the management of COVID-19 patients and for the evaluation of immunological status during vaccination, treatment or in front of emerging variants.<br>

Insight of smart biosensors for COVID‐19: A review

“…Different types of biosensors developed in the laboratory for COVID‐19 are represents in Table 2. [ 46,48,65,78‐86,87,88 ]…”

“…Spiked saliva 90 fM 10-30 s [79] Electrochemical immunosensor Antigens Saliva 19 ng/ml and 8 ng/ml 30 min [80] Multiplexed grating-coupled fluorescent plasmonics biosensor Antigens Serum and dried blood 30 min [81] Field effect transistor (FET)based biosensor Antigen Swab 2.42 Â 10 2 copies/ml - [82] Electrochemical biosensor Antibody Serum 0.96 (IgG) and 0.14 ng/ml (IgM)…”

Large-scale validation of a plasmonic sensor for SARS-CoV-2 pseudo-neutralization with a cohort of food and retail workers

“…41 Another study also demonstrated the performance of SPR for screening antibodies on 120 samples pre-characterized using standard regulatory-approved commercial detection kits available at time of collection. 42 Building on these studies, we applied a rapid BSL-2 "pseudoneutralization" assay 18 to measure the binding inhibition between the viral spike protein and ACE-2 receptor in over 1000 serum samples collected during a 18 month period in a cohort of food and retail workers. The data collected with SPR sensors were validated using a live virus microneutralization assay (BSL-3), the current gold standard assay for SARS-CoV-2-specific antibody, and captured the changes in the humoral response that were consistent with the timescale of vaccination campaigns and SARS-CoV-2 outbreaks.…”