Triple-Branch Catalytic Assembly DNAzyme Motivated DNA Tweezer for Sensitive and Reliable mecA Gene Detection in Staphylococcus aureus.

Staphylococcus aureus (S. aureus, SA) is one of the most common bacteria in nosocomial infections. Sensitive and efficient analysis of methicillin-resistance of SA is crucial for improving the nursing performance of pneumonia. However, methicillin-resistance analysis with favorable sensitivity and specificity in an enzyme-free manner remains a huge challenge. This paper presents the development of a new fluorescent biosensor for detecting mecA gene using a triple-branch catalytic hairpin assembly (CHA) triggered DNAzyme switch-based DNA tweezer. The SA from the samples are immobilized on the plate's surface using the protein A antibody. The biosensor possesses several key features. Firstly, it utilizes dual signal amplification processes, specifically the triple-branch CHA and DNAzyme controlled DNA tweezer-based signal recycling, to enable mecA detection on the plate. This design enhances the method's sensitivity, resulting in a low limit of detection of 1.5 fM. Secondly, the biosensor does not rely on enzymes for mecA analysis, ensuring a high level of stability during target analysis. Lastly, the method demonstrates a remarkable selectivity by accurately distinguishing target sequences from non-target sequences. The proposed biosensor, which does not require enzymes and has a high level of sensitivity, offers a viable platform for the rapid and simple quantification of mecA in SA.