Simultaneous quantification of Escherichia coli O157:H7 and Shigella boydii using a visual-antibody-macroarray

The application of nanoparticles in point-of-care testing (POCT) immunoassays

The Covid-19 pandemic has led to greater recognition of the importance of the fast and timely detection of pathogens. Recent advances in point-of-care testing (POCT) technology have shown promising results for rapid diagnosis. Immunoassays are among the most extensive POCT assays, in which specific labels are used to indicate and amplify the immune signal. Nanoparticles (NPs) are above the rest because of their versatile properties. Much work has been devoted to NPs to find more efficient immunoassays. Herein, we comprehensively describe NP-based immunoassays with a focus on particle species and their specific applications. This review describes immunoassays along with key concepts surrounding their preparation and bioconjugation to show their defining role in immunosensors. The specific mechanisms, microfluidic immunoassays, electrochemical immunoassays (ELCAs), immunochromatographic assays (ICAs), enzyme-linked immunosorbent assays (ELISA), and microarrays are covered herein. For each mechanism, a working explanation of the appropriate background theory and formalism is articulated before examining the biosensing and related point-of-care (POC) utility. Given their maturity, some specific applications using different nanomaterials are discussed in more detail. Finally, we outline future challenges and perspectives to give a brief guideline for the development of appropriate platforms.

Development of a Bacterial Macroarray for the Rapid Screening of Targeted Antibody-Secreted Hybridomas

Hybridoma screening is a key step for the successful generation of high-affinity analyte-specific monoclonal antibodies (MAbs). This work presents an innovative screening method, known as a bacterial macroarray, generated by contact printing of hybridoma cell supernatant samples on a nitrocellulose (NC) membrane initially coated with fluorescein isothiocyanate (FITC)-labeled bacteria. Given that bacterial fixation will be influenced by complex bacterial surface structures, we selected both gram-positive bacteria ( Staphylococcus aureus and Listeria monocytogenes) and gram-negative bacteria ( Escherichia coli O157:H7 and Cronobacter sakazakii) to optimize the fixation conditions for binding to the NC membrane, such as the aperture of the NC membrane, the concentration of bacteria, the dosage of glycerin in the spotting buffer, and the fixation time and temperature. As a result, we found that a better bacterial macroarray could be developed when the spotting buffer, containing 10¹¹ CFU mL^-1 of FITC-labeled bacteria and 15% (V/V) glycerol, was spotted onto a 0.45 µm NC membrane with an incubation of 2 h at 37 °C. Finally, we verified the stability and specificity of the prepared bacterial macroarray by detecting cell cultures with the addition of two MAbs ( Escherichia coli O157:H7 MAb E7 and Cronobacter sakazakii MAb 1E9) to simulate the screening experiments. Here, we describe a bacterial macroarray to efficiently screen the targeted antibody-secreted hybridomas.