| Autor: |
Lew TTS; Institute of Materials Research and Engineering, Agency for Science, Technology and Research (A*STAR), 2 Fusionopolis Way, Singapore 138634, Singapore., Aung KMM; Institute of Materials Research and Engineering, Agency for Science, Technology and Research (A*STAR), 2 Fusionopolis Way, Singapore 138634, Singapore., Ow SY; Institute of Materials Research and Engineering, Agency for Science, Technology and Research (A*STAR), 2 Fusionopolis Way, Singapore 138634, Singapore., Amrun SN; A*STAR Infectious Diseases Laboratories (A*STAR ID Laboratories), Agency for Science, Technology and Research (A*STAR), Singapore 138648, Singapore., Sutarlie L; Institute of Materials Research and Engineering, Agency for Science, Technology and Research (A*STAR), 2 Fusionopolis Way, Singapore 138634, Singapore., Ng LFP; A*STAR Infectious Diseases Laboratories (A*STAR ID Laboratories), Agency for Science, Technology and Research (A*STAR), Singapore 138648, Singapore.; National Institute of Health Research, Health Protection Research Unit in Emerging and Zoonotic Infections, University of Liverpool, Liverpool L69 7BE, United Kingdom.; Institute of Infection, Veterinary and Ecological Sciences, University of Liverpool, Liverpool CH64 7TE, United Kingdom., Su X; Institute of Materials Research and Engineering, Agency for Science, Technology and Research (A*STAR), 2 Fusionopolis Way, Singapore 138634, Singapore.; Department of Chemistry, National University of Singapore, Block S8, Level 3, 3 Science Drive 3, Singapore 117543, Singapore. |
| Abstrakt: |
Rapid and inexpensive immunodiagnostic assays to monitor severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) seroconversion are essential for conducting large-scale COVID-19 epidemiological surveillance and profiling humoral responses against SARS-CoV-2 infections or immunizations. Herein, a colorimetic serological assay to detect SARS-CoV-2 IgGs in patients' plasma was developed using short antigenic epitopes conjugated to gold nanoparticles (AuNPs). Four immunodominant linear B-cell epitopes, located on the spike (S) and nucleocapsid (N) proteins of SARS-CoV-2, were characterized for their IgG binding affinity and used as highly specific biological motifs on the nanoparticle to recognize target antibodies. Specific bivalent binding between SARS-CoV-2 antibodies and epitope-functionalized AuNPs trigger nanoparticle aggregation, which manifests as a distinct optical transition in the AuNPs' plasmon characteristics within 30 min of antibody introduction. Co-immobilization of two epitopes improved the assay sensitivity relative to single-epitope AuNPs with a limit of detection of 3.2 nM, commensurate with IgG levels in convalescent COVID-19-infected patients. A passivation strategy was further pursued to preserve the sensing response in human plasma medium. When tested against 35 clinical plasma samples of varying illness severity, the optimized nanosensor assay can successfully identify SARS-CoV-2 infection with 100% specificity and 83% sensitivity. As the epitopes are conserved within the circulating COVID-19 variants, the proposed platform holds great potential to serve as a cost-effective and highly specific alternative to classical immunoassays employing recombinant viral proteins. These epitope-enabled nanosensors further expand the serodiagnostic toolbox for COVID-19 epidemiological study, humoral response monitoring, or vaccine efficiency assessment. |
