Dual-channel microfluidic paper-based fluorescent immunosensor for concurrent detection of aflatoxin B1 and capsaicin in edible oils

In this study, we developed a fluorescent immunosensor (FIS) based on a dual-channel microfluidic paper-based analytical device (µPAD) for a concurrent detection of aflatoxin B₁(AFB₁) and capsaicin (CAP) in edible oils. The fluorescence-based detection was facilitated using Phycocyanin (PC) as a signal marker. PC, along with AFB₁ or CAP-specific antibodies, was successfully immobilized onto the surfaces of carboxyl-functionalized polystyrene latex nanospheres (LNS), ensuring stable attachment of the proteins. The binding of these immobilized antibodies to their corresponding antigens generated strong, detectable signals on the µPAD following the flow of 35 µL sample solution across the µPAD channels. The signals were collected using a smartphone camera integrated with a 365 nm LED UV light source. The FIS-µPAD system demonstrated enhanced sensitivity for both targets, achieving low detection limits of 0.23 ng/mL and 0.17 ng/mL for AFB₁, and 0.63 ng/mL and 0.75 ng/mL CAP in soybean and corn oil samples, respectively. The accuracy of the method was thoroughly analyzed and cross-validated using standard technique. The new immunosensor, based on the dual-channel µPAD offers an easy-to-use, rapid, cost-effective, and portable platform for the detection of AFB₁ and CAP in edible oils.