Serological immunochromatographic approach in diagnosis with SARS-CoV-2 infected COVID-19 patients

An outbreak of new coronavirus SARS-CoV-2 was occurred in Wuhan, China and rapidly spread to other cities and nations. The standard diagnostic approach that widely adopted in the clinic is nuclear acid detection by real-time RT-PCR. However, the false-negative rate of the technique is unneglectable and serological methods are urgently warranted. Here, we presented the colloidal gold-based immunochromatographic (ICG) strip targeting viral IgM or IgG antibody and compared it with real-time RT-PCR. The sensitivity of ICG assay with IgM and IgG combinatorial detection in nuclear acid confirmed cases were 11.1%, 92.9% and 96.8% at the early stage (1-7 days after onset), intermediate stage (8-14 days after onset), and late stage (more than 15 days), respectively. The ICG detection capacity in nuclear acid-negative suspected cases was 43.6%. In addition, the consistencies of whole blood samples with plasma were 100% and 97.1% in IgM and IgG strips, respectively. In conclusion, serological ICG strip assay in detecting SARS-CoV-2 infection is both sensitive and consistent, which is considered as an excellent supplementary approach in clinical application.

Iron Oxide Nanoparticles Conjugated Monoclonal Antibody for Immunochromatographic Strip Test

In this study, the synthesis of iron oxide nanoparticles (IONPs) and immunochromatographic (ICG) strip test of iron oxide conjugated with monoclonal antibody (IONPs-Ab) have been developed. The IONPs were synthesised using precipitation method and dispersed in water by applying polyethylene glycol coating. Several parameters that affected conjugations of the IONPs-Ab were studied namely iron oxide concentration, antibody volume, stabilizer concentration and the amount of SiPEG coating. From the transmission electron microscopy (TEM) image, the size of IONPs obtained was ~14 nm. Conjugate was tested with the ICG strip test lined with the antigen. The results showed 1.0μl SiPEG coating, 1 M IONPs concentration, 20μl of 1mg/ml antibody volume and 1% bovine serum albumin (BSA) were the optimum. Moreover, the IONPs-Ab was also tested with the Brugian filariasis positive and negative serum samples. The results showed positive result for the patient serum and negative result for the non-patient serum in just 15 minutes.

Enhanced Rapidity for Qualitative Detection of Listeria monocytogenes Using an Enzyme-Linked Immunosorbent Assay and Immunochromatography Strip Test Combined with Immunomagnetic Bead Separation

An enzyme-linked immunosorbent assay (ELISA), immunochromatography (ICG) strip test, and immunomagnetic bead separation (IMBS) system based on a monoclonal antibody were individually developed for the detection and isolation of Listeria monocytogenes in meat samples. The three methods showed a strong reaction with Listeria species and a weak reaction with Staphylococcus aureus. To increase the rapidity of L. monocytogenes detection, combinations of the ELISA and ICG strip test with the IMBS system (ELISA-IMBS and ICG-IMBS) were investigated. In comparative analyses of artificially inoculated meat and samples of processed meat, the ELISA and ICG strip test required 24 h of enrichment time to detect the inoculated meat samples with ≥ 1 × 102 CFU/10 g, whereas the ELISA-IMBS and ICG-IMBS required only 14 h of enrichment. Analyses of naturally contaminated meat samples (30 pork samples, 20 beef samples, 26 chicken samples, 20 fish samples, and 20 processed meat samples) performed by ELISA-IMBS, ICG-IMBS, and API kit produced similar results. The ELISA-IMBS and ICG-IMBS provide a more rapid assay than the individual ELISA and the ICG strip test and are appropriate for rapid and qualitative detection of L. monocytogenes (or Listeria species) in meat samples. With the ICG-IMBS, L. monocytogenes could be detected in meat samples within 15 h and the method has potential as a rapid, cost-effective on-site screening tool for the detection of L. monocytogenes in food samples and agricultural products at a minimum detection level of ~100 CFU/10 g.