A target-responsive and signal-amplified DNA hydrogel biosensor for visual and quantitative detection of Aflatoxin B1

Aflatoxin B1 (AFB1) poses a severe threat to food safety due to its potent carcinogenicity. To address the need for rapid and on-site detection, this study developed a colorimetric biosensor based on an AFB1-responsive DNA aptamer-cross-linked sodium alginate hydrogel. Gold nanoparticles (AuNPs) were encapsulated within the hydrogel as a visual signal reporter. The sensing mechanism relies on target-induced dissociation of aptamer crosslinkers, leading to hydrogel disintegration and release of AuNPs. The hydrogel formulation was optimized regarding sodium alginate concentration and crosslinking conditions. To enhance sensitivity, an Exonuclease I (Exo I)-triggered target recycling strategy was implemented, which amplifies hydrogel network disruption by cleaving and recycling the aptamer. The sensor demonstrated a linear detection range of 0-50 µM, with a detection limit of 12.9 nM, and exhibited high selectivity towards AFB1. This work presents a sensitive, visually readable, and portable platform for mycotoxin detection in food safety applications.