Development of aptamer-based monolithic sorbent in paper devices for lysozyme extraction in foods

Lysozyme (Lyz) is a protein commonly used as a food preservative, but it can cause severe allergic reactions. Detecting trace amounts of Lyz in food is essential, requiring sensitive, reliable, and accessible analytical methods. Aptamers (Apts) are recognition ligands that can be integrated into paper-based devices to offer low-cost and effective platforms for Lyz detection. However, the Apt-paper hybridization as sorptive phase remains insufficiently explored.

In this work, an Apt-functionalized monolith was developed as an affinity sorbent for Lyz determination in foods using thin-film microextraction (TFME). For this purpose, a nitrocellulose piece was coated with a monolithic polymer based on 2-[(methacryloyloxy)ethyl]trimethylammonium chloride to immobilize Apt onto monolith's surface via adsorption. Subsequently, the prepared selective device was used to extract Lyz, evaluating several parameters affecting Lyz retention and elution. The selected conditions were a phosphate buffer at pH 6 for loading and 0.2 M glycine pH 2.0 for elution. The developed TFME method, combined with HPLC-DAD, was applied for the determination of trace Lyz in egg-free and egg-containing foods, achieving satisfactory recoveries (75-107 %), precision (RSD <6.1 %), and limit of detection (0.0085 μg mL^-1). Additionally, the developed Apt-monolith@paper was affordable (<4.5 €/device), stable, and reusable up to 5 extraction cycles.

This work presents, for the first time, an Apt-monolith@paper for Lyz extraction from food samples. This strategy paves the way for advancements in analyzing proteins or hazardous compounds in food, contributing to quality control and safety.