Rapid detection of Cd²⁺ ions in rice using DNAzyme gated graphene field-effect transistor

Cadmium-contaminated rice poses a serious threat to public health, necessitating rapid screening methods. Unfortunately, traditional cadmium detection techniques are often cumbersome and expensive, making them unsuitable for on-site applications. In this study, we developed a graphene field-effect transistor (GFET) biosensor with Deoxyribozyme (DNAzyme) probes in binding mode at the graphene channel. By rationally redesigning a traditional catalytic DNAzyme, we suppressed its autocatalytic cleavage activity while fully retaining its high-specificity binding affinity for Cd²⁺, thus creating a pure binding-mode probe. The probe was subsequently immobilized on the graphene channel of a GFET sensor to capture Cd²⁺. The surface charge change induced by Cd²⁺ accumulation is efficiently converted by the GFET into measurable electrical signals, enabling rapid and accurate quantitative detection of Cd²⁺ in rice samples with an ultra-low limit of detection (LOD) of 0.3 μg/L and a recovery rate up to 94.74%. This study provides a promising platform for rapid, accurate, and on-site detection of heavy metal contamination in agricultural products.