Theoretical and Experimental Comparison of Different Formats of Immunochromatographic Serodiagnostics

Abstract

In this study, a comparative theoretical and experimental analysis of two immuno-chromatographic serodiagnostics schemes, which differ in the immobilization of immunoreagents and the order of the formation of immune complexes, is performed. Based on the theoretical models, the assays are characterized to determine which scheme has a higher quantity of the detected complex and thus ensures the sensitivity of the analysis. The results show that for the effective detection of low-affinity antibodies, the scheme involving the immobilization of the antigen on gold nanoparticles and the antibody-binding protein on the test strip was more sensitive than the predominantly used scheme, which inverts the immunoreagents’ locations. The theoretical predictions were confirmed by the experimental testing of sera collected from tuberculosis patients.

Development of a Gold Nanoparticle-Based Lateral-Flow Immunoassay for Pneumocystis Pneumonia Serological Diagnosis at Point-of-Care

“…(Figure 1). Although the traditional LFIA schemes for antibody detection uses AuNPs conjugated with an immunoglobulinbinding protein and the pathogen's antigen immobilized in the analytical zone (test line), some studies have shown that a less conventional scheme using AuNPs directly conjugated with pathogen's antigen molecules for detection of serum antibodies can achieve greater diagnostic sensitivity (Sotnikov et al, 2015(Sotnikov et al, , 2018. This increase in sensitivity is achieved by targeting the capture of the antibodies of interest in the conjugation process, due to the specific interaction of those antibodies with the corresponding antigens present in the conjugates.…”

Lateral Flow Serodiagnosis in the Double-Antigen Sandwich Format: Theoretical Consideration and Confirmation of Advantages

“…In real samples, the concentration of specific antibodies against individual antigens rarely exceeds 2 µM, even in hyperimmune sera [ 36 ]. Therefore, a decrease in the color intensity to an undetectable limit is unlikely.…”

“…To overcome this limitation, an alternative immunochromatographic serodiagnostics format has been proposed, in which the label is conjugated to the antigen, and an immunoglobulin-binding protein is sorbed in the analytical zone [ 32 , 33 , 34 , 35 , 36 , 37 ]. This approach prevents the inclusion of the label in complexes with nonspecific immunoglobulins.…”

“…The problem of signal attenuation, however, remains, because nonspecific immunoglobulins react with immunoglobulin-binding proteins in the analytical zone ( Figure 1 B). However, the sorption capacity of this zone on the test strip is significantly higher (about an order of magnitude) than the sorption capacity of the preparations of nanodispersed marker particles [ 36 ]. Therefore, the binding in the analytical zone of nonspecific antibodies to a lesser extent affects the formation of detectable complexes: immunoglobulin-binding protein–specific antibody-antigen-label.…”

Immunochromatographic System for Serodiagnostics of Cattle Brucellosis Using Gold Nanoparticles and Signal Amplification with Quantum Dots

“…Blocking immunoglobulin-binding sites on the surface of the label by nonspecific immunoglobulins leads to a reduction in the signal, which in turn makes it difficult to interpret the results of the assay accurately [20]. Therefore, an increase in sensitivity is most in demand for immunochromatographic serodiagnosis [21,22]. In a number of works, the use of quantum dots (QDs) was suggested as a means to increase the sensitivity of ICA [23][24][25][26][27].…”