Fast blue B functionalized silica-polymer composite to evaluate 3,5-dihy-droxyhydrocinnamic acid as biomarker of gluten intake

Celiac disease is an immune-mediated systemic disorder elicited by gluten and related prolamines in genetically susceptible individuals. The current treatment is a strict and lifelong gluten-free diet. However, compliance with the gluten-free diet is not always adequate and many food products contain low concentrations of gluten. The determination of dietary transgressions is a challenge for patients, physicians and dietitians. Alkylresorcinols (AR) have been proposed as sensitive and specific biomarkers of gluten consumption. In this work silica-polymer composites doped with fast blue B reagent (FB) have been used to estimate alkylresorcinols in biological samples. The proposed colorimetric device was synthetized by immobilizing FB into polydimethylsiloxane-tetraethylortosilicate composite. The assay was based on the spontaneous release of FB to the solution con-taining AR (3,5-dihydroxyhydrocinnamic acid, DHCA) and the azocomplexe formation (520 nm). The response was evaluated with UV-vis spectroscopy and chromatography (in-tube SPME-Capillary LC-DAD) to isolate DHCA signal. The spectroscopic analysis can be used as a screening tool to differentiate positive and negative samples. Meanwhile, the chromatographic assay was necessary to isolate DHCA response in positive samples. LOD was 60 ng mL-1 by adding a SPE step. Precision provided adequate results (RSD < 15%). Preliminary studies in urine samples displayed successful results, showing DHCA can be used as biomarker of gluten intake. The here pro-posed methodology clearly simplifies the dietary transgression evaluation thanks to the development of a pre -screening tool before the chromatographic analysis.