Dual-Mode Immunochromatographic Biosensor Enhanced With CuS@Au-Nanocomposites for Rapid Detection of <i>Shigella sonnei</i>

Shigella sonnei (S. sonnei) has high infectivity and pathogenicity and can cause severe bacterial dysentery. Thus, it is urgent to develop a fast and convenient biosensor for detecting S. sonnei to ensure public health and food safety. This article introduces a novel dual-mode immunochromatographic test strip (DITS) biosensor that can simultaneously detect S. sonnei using dual colorimetric and photothermal modes. The strip employs the aptamer and goat anti-mouse antibody for the test line (T-line) and control line (C-line) formation, respectively. By forming a composite of copper sulfide (CuS) and gold (Au) nanoparticles for the synthesis of CuS@Au nanocomposites (NCs), the detection performance of the biosensor has been enhanced. The CuS@Au-NCs were conjugated to S. sonnei antibody (Ab) to form CuS@Au@Ab, thereby preparing the CuS@Au@Ab-DITS biosensor. Compared to traditional colorimetric single-mode detection, this sensor combines colorimetric and photothermal methods for dual-mode detection, thus facilitating the detection results more accurately and with high reliability. The results are observed visually in the colorimetric mode and recorded using a thermal infrared imager for the photothermal mode detection under 808 nm infrared laser irradiation at the T-line. The results indicate that the detection limit of this sensor is <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1\times 10^{{4}}$ </tex-math></inline-formula> CFU/mL with a detection time of 10 min. The proposed CuS@Au@Ab-DITS in this experiment offers the potential for detecting S. sonnei, contributing to public health and food safety.