4D-printed ELISA needle panel meter

Enzyme-linked immunosorbent assay (ELISA) is commonly used to detect and quantify antibiotics in food samples. To realize on-site chloramphenicol (CAP) ELISA without any chromogenic or fluorogenic analysis, we utilized the digital light processing four-dimensional printing (4DP) technique and 2,2'-(ethyl enedioxy)diethanethiol (EDT)-incorporated resins to fabricate a panel meter featuring a redox-responsive needle. It exhibited [hydrogen peroxide (H₂O₂)]-dependent bending when the oxidation of the thioether groups in the copolymer induced imbalanced swelling between the printed EDT-incorporated and nonresponsive layers. We optimized the coating of anti-CAP antibodies on the panel surfaces to perform competitive ELISA. Based on the competition between CAP and CAP-labeled horseradish peroxidase (CAP-HRP), the bound CAP-HRP eliminated the additionally added H₂O₂, resulting in [CAP]-dependent bending of the needle, with a method detection limit of 2.5 pg mL^-1. We validated the reliability and applicability of this analytical method by analyzing salmon, shrimp, white meat, pork, honey, and milk samples with their spike analyses and compared the results with those obtained from conventional ELISA, using 3,3',5,5'-tetramethylbenzidine as a chromogenic substrate and a microplate reader for detection. Our results demonstrate the capability and applicability of 4DP technologies in fabricating smart redox-responsive sensing devices to advance conventional immunochemical assays for on-site quantitative chemical analyses.