Selective detection of Pb²⁺ ions based on a graphene field-effect transistor gated by DNAzymes in binding mode

Heavy metal contamination has become a severe threat to dairy products through contaminated feed and the environment water. Among them, Pb(II) is highly toxic to the human body even under minimal exposure. Therefore, establishing a fast and sensitive Pb²⁺ detection technology is significant for rapid screening of vast number of dairy products. Hererin, we report the development of a sensitive and selective Pb(II) biosensor based on a solution-gated graphene transistor (SGGT) with the gate modified by Pb²⁺-dependent DNAzyme probes. It has also been explored that the DNAzymes working in simple binding mode integrate better with the SGGT than those working in normal catalytic mode, showing significantly stronger channel current responses and lower detection limit down to 0.39 μg/L (or 1.9 nM). Finally, the biosensor was practicably applied to the detection of lead ions in pure milk samples with a high recovery rate. We believe that this work reveals the best strategy for integrating metal ion dependent DNAzyme probes with SGGT sensing platforms to selectively and sensitively detect many metal ions.