Rapid and sensitive detection of Staphylococcus aureus assisted by polydopamine modified magnetic nanoparticles

Pathogens cause significant morbidity and mortality to humans. Thus, development of fast and reliable methods for detection and identification of pathogens is urgently needed to increase protection level of public health and ensure the safety of consumers. Herein, a rapid and sensitive method has been developed for Staphylococcus aureus (S. aureus) detection based on the dual role of polydopamine modified magnetic nanoparticles (PDA@Fe₃O₄ NPs) combined with polymerase chain reaction (PCR) and capillary electrophoresis (CE). The core-shell type structure PDA@Fe₃O₄ NPs were prepared, which are spherical, about 152 ± 20 nm in diameter and the PDA shell is about 17.5 ± 1.6 nm. PDA@Fe₃O₄ NPs play a dual role including efficient capture of bacteria and extraction of DNA. In the pH range of 3.0-7.0, the capture efficiency of S. aureus by PDA@Fe₃O₄ NPs was more than 95% in 5 min. The adsorption capacity of the PDA@Fe₃O₄ NPs for S. aureus is 1.2 × 10⁸ cfu mg^-1. The efficient capture and concentration of bacteria from large volumes of samples by PDA@Fe₃O₄ NPs avoids the time-consuming culture-enrichment prior to PCR. Interestingly, PDA@Fe₃O₄ NPs were also found to be efficient adsorbents for extraction of genomic DNA from pathogens based on the electrostatic interaction. The process can be finished in 25 min. The PDA@Fe₃O₄ NPs based solid phase extraction combined with PCR and CE allows for detecting the order of 10² cfu mL^-1S. aureus in tap water and orange juice samples. The whole process takes < 5.5 h. The developed method would provide a promising platform for rapid and sensitive detection of pathogens.