Hairpin-aptamer Conformational Switching Assisted Dual-signal Ratiometric Detection of Aflatoxin B1 Based on Liquid Exfoliated Graphene/Ti3C2 MXene Nanocomposite

Aflatoxin B1 (AFB1) is a highly toxic mycotoxin and widely distributed in food matrixes, posing a serious threat to human health. In this work, a novel sensing platform based on liquid exfoliated graphene/Ti 3 C 2 MXene (LEG/Ti 3 C 2 MXene) nanocomposite was proposed to achieve ultrasensitive detection of trace AFB1 in response to the urgent issue, in which the LEG/Ti 3 C 2 MXene nanocomposites modified indium tin oxide (ITO) electrode acted as transducer, ferrocene (Fc) labeled aptamer (Fc-Apt) and methylene blue (MB) labeled complementary DNA (MB-cDNA) functioned as dual-signal probes, and the conformational change of hairpin-aptamer was regarded as signal “on-off” switch. The irregular Ti 3 C 2 MXene flakes interspersed between LEG sheets layer provided assistance in enhancing sensing performance, specifically, it not only effectively reduced the self-stacking and increased the specific surface area, but also provided multiple interlayer spacing to improve electron transfer efficiency. In the presence of AFB1, its competition with MB-cDNA led to the reappear of hairpin structure for Fc-Apt and the releasing of MB-cDNA, resulting in the removal of MB and fixing Fc close to the electrode surface. As a result, the peak current ratio of Fc to MB (I Fc to I MB ) would change accordingly, which served as the basis for qualitative analysis of AFB1. Under the optimal conditions, the constructed aptasensor exhibited excellent sensitivity with a wide linear range from 0.0001 to 100 ng/mL and a low limit of detection (LOD) of 0.041 pg/mL, as well as satisfactory selectivity, reproducibility, and stability, revealing its promising potential applications in food safety monitoring.