Affinity of aptamers binding 33-mer gliadin peptide and gluten proteins: Influence of immobilization and labeling tags

• Affinity of anti 33-mer peptide aptamer was evaluated by various techniques.
• Unlike other antipeptide aptamers, it recognizes the whole protein with minimal loss in affinity.
• Any modification at 5′ end led to a decrease in affinity but at different extent.
• 6-FAM was the most deleterious marker molecule.
• Biotin modification seems to be less harmful than thiol modification, so recommended for analytical purposes.

Aptamers are starting to increase the reagents tool box to develop more sensitive and reliable methods for food allergens. In most of these assays, aptamers have to be modified for detection and/or immobilization purposes. To take full advantage of their affinity, which decisively influence the detectability, these modifications must be faced rationally. In this work, a recently developed aptamer for an immunotoxic peptide of gliadin associated to celiac disease is used in different configurations and modified with various markers and anchored groups to evaluate the influence of such modifications on the real affinity. The interaction in solution with the peptide is strong for a relatively small molecule (Kd = 45 ± 10 nM, 17 °C) and slightly stronger than that for the immobilized intact protein due to a cooperative binding effect. Comparatively, while only minor differences were found when the peptide or the aptamer were immobilized, labeling with a biotin resulted preferable over fluorescein (Kd = 102 ± 11 vs 208 ± 54 nM, 25 °C). These findings are of prime importance for the design of an aptamer-based analytical method for gluten quantification.

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