The detection of IgG class antibodies against SARS-CoV-2 nucleocapsid protein by application of nanoparticles

- OBJECTIVE: Enzyme-linked immu-nosorbent assay (ELISA) is a widely used biochem-ical analytical method for the detection of a bio-markers, through a specific antigen-antibody reac-tion. A common with ELISA is the amount of con-crete biomarker falling below the detection limit. Thus, the approach that will contribute to enhanced sensitivity of enzyme-linked immunosorbent assay is of great importance for medical practice. To ad-dress this issue, we used nanoparticles to improve the detection limit of traditional ELISA.MATERIALS AND METHODS: 80 samples were used, for which the presence of IgG antibodies against SARS-CoV-2 nucleocapsid protein were already determined qualitatively. We tested the samples using an in vitro ELISA kit [SARS-CoV-2 IgG ELISA, COVG0949 (NovaTec, Leinfelden-Ech-terdingen, Germany)]. Additionally, we tested the same sample with the same ELISA kit but with the addition of 50 nm diameter citrate-capped silver nanoparticles. The reaction was performed, and data were calculated according to manufacturer guidelines. To measure ELISA results absorbance (optical density -OD) at 450 nm was read.RESULTS: Greater absorbance values have been revealed in case of silver nanoparticles ap-plication (66 cases, 82.5%, p<0.05). ELISA with application of nanoparticles classified 19 equiv-ocal cases as positive and 3 equivocal ones as negative, 1 negative case as equivocal.CONCLUSIONS: Our findings suggest that nanoparticles can be used to improve the sen-sitivity of ELISA method and increase the de-tection limit. Thus, it is logical and desirable to enhance the sensitivity of ELISA method by ap-plication of nanoparticles; the approach is low cost and with a positive impact on accuracy.