Aptamer-conjugated magnetic Fe3O4@Au core-shell multifunctional nanoprobe: A three-in-one aptasensor for selective capture, sensitive SERS detection and efficient near-infrared light triggered photothermal therapy of Staphylococcus aureus

Early and accurate diagnosis of pathogenic bacteria is essential to prevent further infection from spreading and multiplying. Herein, an aptamer (Apt) biosensor based on Fe3O4@Au nanocomposites (NCs) has been proposed for capture, surface-enhanced Raman scattering (SERS) detection, and photothermal therapy (PTT) of S. aureus. Fe3O4@Au NCs become SERS substrate and photothermal agent due to superior surface plasmon properties and photothermal ability, while the aptamer immobilized on surface of Fe3O4@Au NCs acts as a capture agent. The detection limit of optimized Fe3O4@Au-Apt aptasensor for S. aureus is 25 cfu/mL, and cell capture efficiency (CCE) is as high as 68%. Moreover, our Fe3O4@Au-Apt NCs have high photothermal conversion efficiency of 39.28%, which have been proven as an excellent photothermal agent. As verified by experiments, Fe3O4@Au-Apt aptasensor is not only a promising tool to detect and photothermally inactivated S. aureus in milk samples, but also exhibits negligible cytotoxicity and good biocompatibility. This work shows a promising multifunctional nano-platform, which has great potential in specific recognition, sensitive SERS detection and PTT of S. aureus.