DNA tetrahedrons based DNA microcapsules for sensitive fluorescence sensing of Staphylococcus aureus.

A sensitive fluorescence (FL) biosensor was developed for the detection of Staphylococcus aureus (S. aureus) using DNA tetrahedrons (DTNs) based stimuli-responsive DNA microcapsules. FAM-labeled DTNs were initially encapsulated within the inner pores of DNA microcapsules. Owing to the physical shielding effect of the DNA shell, no FL signal was detected, maintaining the biosensor in a "fluorescence off" state. Upon exposure to S. aureus, the aptamer specifically bound to the target bacteria, triggering the disassembly of the DTN-loaded DNA microcapsules. This led to the controlled release of FAM-labeled DTNs and the subsequent recovery of the FL signal. Based on this, sensitive and specific detection of S. aureus was achieved with a detection limit of 0.36 CFU∙mL- 1. Moreover, satisfactory results were obtained for S. aureus detection in spinach leaves, milk and human serum, demonstrating that the proposed sensing system held promising application prospects for the detection of S. aureus in food and related complex matrices.