Utilization of Eco-friendly Imidazolium-Based Ionic Liquids for Gluten Extraction: Investigating the Influence of Side Chains and Anions

Abstract

Gluten is a well-known food allergen globally, capable of triggering immune responses in both celiac and non-celiac gluten-sensitive individuals. Gluten comprises two major proteins: glutenin and gliadin. Gliadin, in particular, possesses a unique hydrophobic amino acid sequence. The Food and Drug Administration asserts that the toxicity of gliadin cannot be eliminated through fermentation and hydrolysis processes. A common approach to addressing gluten allergies is to adopt a gluten-free diet. However, the hydrophobic nature of gluten makes its detection challenging. Analysts often resort to using organic solvents or employing multiple procedures to denature gluten for extraction. Its worth noting that while organic solvents can rapidly extract gluten from a sample, they may also alter antibodies, leading to erroneous bio-test results. Ionic liquid (IL) is a highly adaptable green chemical compound consisting of organic salts. We modified imidazolium, a cationic structure, with various carbon side chain lengths (C=0, 1, 3, 5, 7, 9, and 12), and combined it with organic and inorganic anions (e.g., OMs-, Cl-, F-, NO{not}3-, HSO4-, and H2PO4-). We used different IL-to-water ratios to assess gluten solubility. We measured the solubility of gliadin in various imidazolium ILs and conducted kinetic studies on the dissolution of gliadin in 1% [C5DMIM][OMs]aq. Additionally, circular dichroism (CD) spectroscopy and enzyme-linked immunosorbent assay (ELISA) were employed to evaluate the structural changes in gliadin and its interaction with antibodies after treatment with 1% [C5DMIM][OMs]aq. An XTT assay was conducted to assess the cytotoxicity of [C5DMIM][OMs]aq on N2a cells. Our research findings indicate that 1% [C5DMIM][OMs]aq demonstrated excellent gluten solubility, dissolving more than 3000 ppm of gluten within 5 minutes. Importantly, [C5DMIM][OMs]aq did not disrupt the gluten structure, did not impede antibody binding to gluten, and exhibited no cell toxicity. This report highlights [C5DMIM][OMs] as a promising extraction solution for gluten detection.