Dual-mode colorimetric–fluorometric immunoassay for foodborne parasitic infection

Immunoassays are the primary method used for detection of foodborne parasitic infection. The nanomaterials used in these assays often present challenges such as complex preparation requirements and low stability during long-term storage and transport. Herein, based on cost-effective K₃[Fe(CN)₆]-mediated in-situ generated CuFe Prussian blue analogues (CuFe-PBA) and quinoxaline derivatives with high fluorescence, a dual-mode immunoassay was proposed for foodborne parasitic infection. This platform is relied on the restoration of K₃[Fe(CN)₆] by ascorbic acid (AA). In addition to this process, K₄[Fe(CN)₆]-triggered the generation of CuFe-PBA, and the enhanced fluorogenic reaction of dehydrogenated AA and o-phenylenediamine (OPD) occur sequentially. Without complex probes preparation, the assay enabled the rapid on-site detection of ALP and foodborne parasitic infection through a colorimetric mode accessible via smartphone and offered enhanced sensitivity through a fluorescent mode. The method was used for the detection of ALP, achieving detection limits of 0.38 U/L and 0.03 U/L for colorimetric and fluorescence modes, respectively. Subsequently, the dual-mode immunoassay was applied to Trichinella spiralis infection. The sensitivity and specificity of both the colorimetric and fluorescence modes were 100 % in 950 pig serum samples. This immunosensor provides a universal analysis tool for the accurate, cost-effective and highly sensitive detection of foodborne parasitic infection.