Dual-recognition aptazyme-driven DNA nanomachine for two-in-one electrochemical detection of pesticides and heavy metal ions

Bi-detection of chemical risks in different kinds exhibited an increasing significance for food security considering their general concurrence and synergetic toxicity. In this study, a simple two-in-one electrochemical biosensor was fabricated for sensitive and efficient measurement of pesticides and heavy metal ions utilizing a specially designed dual-recognition aptazyme beacon (DRAB). The self-blocked DRAB containing aptamer and enzyme strand of DNAzyme was firstly activated by pesticides induced conformational change and then achieved a specific cleavage of methylene blue tagged signal probe (SP) in the presence of targeted metal ions. The released DRAB-pesticides complex could bind adjacent SP for another cyclic cleavage, thus forming a signal enhanced DNA nanomachine. By optimizing the 3 ' terminal of DNAzyme, an improved aptazyme with a replaceable arm was developed and enabled a versatile detection of various food contaminants possessing selected aptamers. Taking chlorpyrifos and Pb2+ as the testing model, we demonstrated remarkable sensor performances with high sensitivity, selectivity and practicability in fresh fruit and vegetables samples. This two-in-one biosensor realized a bi-detection in single analytical system, thus eliminating additional design and optimization for the other target. This study brings new investigation on bi-identification of aptazyme and its application to on site detection of food contaminants.