Fluorescein Isothiocyanate Labeling Antigen-Based Immunoassay Strip for Rapid Detection of Acidovorax citrulli

Bacterial coloration immunofluorescence strip for ultrasensitive rapid detection of bacterial antibodies and targeted antibody-secreting hybridomas

The indirect enzyme-linked immunosorbent assay (ELISA) is the gold standard method for monoclonal antibody (McAb) detection and plays a unique role in the preparation of bacterial antibodies. To solve the laborious issues associated with indirect ELISA, a novel bacterial coloration immunofluorescence strip (BCIFS) for antibody detection using colored bacteria instead of a labeled antibody as the antigen and tracer simultaneously and goat anti-mouse IgG as the test line was developed. The affinity range survey of BCIFS indicated that hybridoma cell cultures of E. coli O157:H7 (D3, E7) and Vibrio parahemolyticus (H7, C9) were detected, which complied with the results of indirect ELISA. Compared with the traditional indirect ELISA, the BCIFS sensitivity for E7 cell cultures, ascites, and purified antibodies was at least 4-fold more sensitive, and the BCIFS cross-reactivity for E7 cell cultures was almost consistent with that of indirect ELISA. In addition, the BCIFS isotypes for E. coli O157:H7 cell cultures and Vibrio parahemolyticus were IgG2a and IgG1, respectively, which were identical to the indirect ELISA. Furthermore, the BCIFS method was confirmed by McAb preparation, effective antibody use, and targeted antibody-secreted hybridoma preparation and screening, which showed excellent performance and substitution of the indirect ELISA method. Combined with methylcellulose semisolid medium, BCIFS offers a novel, easy to operate, rapid preparation method for antigen-specific hybridomas. This is the first report using BCIFS instead of indirect ELISA for bacterial antibody detection and application in different samples, which demonstrates a rapid and powerful tool for antibody engineering.

Functional nanozyme mediated multi-readout and label-free lateral flow immunoassay for rapid detection of Escherichia coli O157:H7

To overcome the drawbacks of antibody labeling dependence and single-readout system in the conventional lateral flow immunoassays (LFIAs) as well as the non-targeted combination of new capture agents reported recently for pathogen detection, in this work, a multi-readout and label-free LFIA was proposed for rapid detection of Escherichia coli O157:H7 (E. coli O157:H7) based on a nanozyme-bacteria-antibody sandwich pattern. A type of functional nanozyme-mannose modified Prussian blue (man-PB), was introduced as the recognition agent as well as signal indicator. Apart from original signal intensity on the T-line, the peroxidase-like catalytic activity-driven generation of colorimetric signal could be used as another format of quantitation. Importantly, such LFIA could exhibit excellent performance for target pathogens detection separately with a quantitative range of 10²-10⁸ cfu·mL^-1 and a low detection limit of 10² cfu·mL^-1 based on different readout formats, indicating the application potential of the proposed LFIA in real samples.

New Functional Tracer-Two-Dimensional Nanosheet-Based Immunochromatographic Assay for Salmonella enteritidis Detection

The rapid monitoring of foodborne pathogens by monoclonal antibody (McAb)-based immunochromatographic tests (ICTs) is desirable but highly challenging as a result of the screening obstacle for a superior performance probe, which will greatly determine the capture efficiency of targets and the sensitivity of the immunoassay. In this work, on the basis of two-dimensional (2D) nanosheets (including MoS₂ and graphene) as the extraordinary capture probe and signal indicator, we fabricated a label-free ICT method for Salmonella enteritidis detection. Especially, without the customarily labeled antibody probe, these 2D versatile probes presented strong capture ability toward bacteria by directly assembling onto the surface of bacteria. An ideal analytical performance with high sensitivity and specificity was achieved by virtue of the novel nanosheet-bacteria-McAb sandwich format. On the basis of MoS₂ 2D nanosheets as a fabulous probe element, the developed ICT exhibited a lowest detectable concentration of 10³ colony-forming units/mL for S. enteritidis and could be well-applied in drinking water and watermelon juice samples. By the smart design, this work removes a series of conditionality issues of traditional double antibody sandwich-based ICTs and can give a new application direction for 2D nanosheet materials in the rapid detection field.