| The continued spread and infection of the novel coronavirus(SARS-CoV-2)worldwide has had a huge impact on the health of people's lives and has become a serious public health problem.There is still no specific medicine for this viral infection,so early and rapid screening and effective and accurate diagnostic tools are essential to control the development of the outbreak.Although nucleic acid testing is currently used as the main detection tool for diagnostic,it has some disadvantages in terms of rapid screening in a large area.The detection of specific antibodies produced against SARS-Co V-2 infection in the organism can be used as a diagnostic indicator for confirming the diagnosis of the 2019 coronavirus disease(COVID-19),in which anti-SARS-Co V-2 immunoglobulin M(Ig M)and immunoglobulin G(Ig G)are mainly used.The detection of COVID-19 antibodies is an effective complement to nucleic acid testing,which not only improves the accuracy of the test results but also has great potential value in the rapid screening of a large number of suspected patients.In this study,a surface-enhanced Raman scattering(SERS)-based lateral flow immunoassay(LFIA)method was designed for the rapid and highly sensitive detection of anti-SARS-CoV-2 IgM/IgG.SERS-LFIA combines SERS detection technology and LFIA detection technology,which has the advantages of rapid,simple,highly sensitive,and quantitative detection,and meets the requirements of point-of-care testing(POCT).The experimental method was developed by preparing a high-performance SiO2@Ag SERS substrate and establishing a SiO2@Ag-based SERS-LFIA detection method.An S protein antibody single-channel assay model was used to optimize and evaluate the detection performance of our proposed SERS-LFIA method.The diagnostic application of the proposed Si O2@Ag-based SERS-LFIA assay was further evaluated by the analysis of clinical serum samples.The main results were as follows:1.A novel two-layer DTNB Raman molecule-loaded SiO2@Ag core-shell nanomaterial was prepared as a SERS-enhanced substrate.The PEI-mediated seed growth method was used for the controlled synthesis of SiO2@Ag nanomaterials and modified with two-layer of DTNB Raman molecules to provide a stronger source of SERS signal.Through a series of characterization experiments such as TEM,UV-vis,and zeta potential,the results showed that the Si O2@Ag SERS label has the advantages of good homogeneity,less agglomeration,and strong SERS activity,and can be well suited for immunochromatographic test strips.2.A SiO2@Ag-based SERS-LFIA assay was developed and optimized.The recombinant S protein was modified on the SiO2@Ag to form a SERS tag,and the NC membrane,the loading buffer,and the concentration of S protein modification of the test strips were optimized to achieve a highly sensitive quantitative detection of S protein antibodies with a detection limit of 1 pg/m L.The reproducibility and stability of the prepared test strips were found to be good,indicating that the SiO2@Ag-based SERS-LFIA assay is feasible to be applied to real clinical samples.3.The first SERS-LFIA method was proposed for the detection of anti-SARS-CoV-2IgM/Ig G.SiO2@Ag-based SERS-LFIA test strips were established for the detection of anti-SARA-CoV-2 IgM/IgG,which was analyzed the testing performance of clinical serum samples.We used a selected COVID-19 serum sample as an example and verified the positivity with commercial colloidal gold test strips to strengthen the accuracy of the subsequent experimental results.In the SERS-LFIA model,its detection limit reached1.28×107-fold dilution,while the colloidal gold visualization resulted in 1.6×104-fold dilution.Thus,the sensitivity of the Si O2@Ag-based SERS-LFIA method proposed in this study was 800 times higher than that of the conventional colloidal gold method test strips,demonstrating a wide dynamic detection range.The diagnostic detection rate and specificity were 100%for 68 serum samples,and these results were plotted as ROC(Receiver Operating Characteristic)curves with an AUC(Area Under Curve)result of 0.997-1,revealing the high diagnostic value of the Si O2@Ag-based SERS-LFIA assay proposed in this study. |
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