The Development of a Photothermal Immunochromatographic Lateral Flow Strip for Rapid and Sensitive Detection of Bisphenol A in Food Samples

A novel quantitative photothermal-sensing immunochromatographic assay (PT-ICA) with high sensitivity was developed for the detection of bisphenol A (BPA). Gold acid chloride trihydrate (HAuCl4·3H2O) was first reduced by citric acid trisodium salt (C6H5Na3O7) to form Au nanoparticles and adsorbed on the surface of black phosphorus nanosheets to form a black phosphorus-Au (BP-Au) complex. The antibody against BPA was then coupled to the BP-Au complex to form the black phosphorus-Au-antibody (BP-Au-Ab) photothermal probe for capturing BPA in samples. During the detection, the precoated antigen BPA-bovine serum albumin (BPA-BSA) on the T line and free BPA molecules in the sample would competitively bind to the limited BP-Au-Ab photothermal probes. After that, the exothermic process under an 808-nm laser was recorded using an infrared thermal imager, which represented the concentration of BPA in the samples. The PT-ICA demonstrated high sensitivity with a limit detection of 0.24 ng/mL, which was 6.25 times lower than that of the visual-ICA. In addition, the assays were highly specific, only minor cross-sensitivity occurred between BPA and 4-cumylphenol. The optimized assay was applied in the detection of BPA in different food samples with recoveries ranging from 75.91 to 119.59%. Finally, the PT-ICA was verified using a commercial enzyme-linked immunosorbent assay (ELISA) kit. The results of the developed assay showed good agreement with that of the ELISA kit. The optimized PT-ICA required a shorter detection time (approximately 30 min) than the ELISA kit (approximately 2 h), which has potential applications in the detection field.