A simple, highly sensitive biosensor for S. aureus detection is becoming increasingly important in human health and safety. In this work, a hairpin probe-mediated DNA circuit for the detection of the mecA gene of S. aureus was reported cascading Exo III-assisted cycling signal amplification and the DNAzyme-mediated cleavage reaction. In the presence of the target mecA gene, the recognition and hybridization between HP1 and mecA can trigger Exo III and DNAzyme-mediated signal amplification and further release numerous ATMND, resulting in an enhanced fluorescence response, which serves as a resp...