High-affinity aptamer of allergen β-lactoglobulin: Selection, recognition mechanism and application

β-Lactoglobulin (β-Lg), the main allergen of milk and dairy products, is capable of causing food allergies in some groups, especially infants and young children. Therefore, a sensitive, efficient and rapid method for β-Lg detection is urgently needed to protect allergy sufferers. In this study, aptamers against β-Lg were successfully selected by capture-SELEX. The aptamer Lg-18 was observed by isothermal titration calorimeter (ITC) and fluorescence assay to have high affinity to β-Lg. Furthermore, circular dichroism indicated that the secondary structure of Lg-18 contains typical hairpin structure, and thermodynamic parameters during bonding showed that the binding of aptamer Lg-18 to β-Lg was an enthalpically driven enthalpy-entropy compensation process. Docking simulations of Lg-18 and β-Lg were performed to further theoretically explain the experimental results and elucidate the recognition mechanism. Finally, the aptamer Lg-18 was used to construct a novel fluorescence-surface enhanced Raman scattering dual-mode aptasensor for efficient and sensitive detection of the allergen β-Lg. The aptasensor exhibited a broader linear range from 10−5000 ng/mL, with a lower detection limit of 0.05 ng/mL. The method showed good recoveries in spiked amino acid formula powder. These results demonstrated that the aptasensor can be applied for the detection of β-Lg in real samples with a good stability.