Micropipette Tip-Based Immunoassay with Electrochemical Detection of Antitissue Transglutaminase to Diagnose Celiac Disease Using Staples and a Paper-Based Platform.

In this work, 1-200 μL polypropylene micropipette tips were used as platforms for performing immunoassays after converting their inner surfaces on a capture zone for the analyte of interest. We have used a micropipette-tip immunoelectroanalytical platform for the detection of antitissue transglutaminase (IgA), the main biomarker for celiac disease. Modification of the tip wall with poly-l-lysine allowed adsorption of tissue transglutaminase (tTG), which will capture later anti-tTG (IgA) antibodies developed in celiac-affected people. A sandwich-type format was followed, incubating simultaneously the analyte and the detection antibody, labeled with horseradish peroxidase. With this new application for an extremely common lab material, we can perform quantitative analysis by dispensing the liquid into a low-cost and miniaturized staple-based paper electrochemical platform. The analytical signal was the reduction of the enzymatically oxidized substrate, recorded chronoamperometrically (i-t curve). The intensity of the current obtained at a fixed time after the application of the cathodic potential followed a linear relationship with anti-tTG (IgA) concentration. The relative standard deviation obtained for immunoassays performed in different tips indicates the adequate precision of this new methodology, which is very promising for decentralized analysis. Negative and positive controls produced results that were in accordance with those obtained with spectrophotometric enzyme linked-immunosorbent assays.