A photothermal colorimetric dual-signal sensor for Staphylococcus aureus in food based on CuS nanoparticles

Abstract

Staphylococcus aureus (S. aureus) is a common foodborne pathogenic organism, and rapid detection with high sensitivity and targeted killing are essential for controlling its spread. Therefore, a sandwich structure of magnetic bead-target bacteria-copper sulfide was constructed in this paper. The photothermal conversion function and peroxidase (POD) activity of CuS NPs were utilized to establish a dual sensing platform for temperature and color rendering, that is, after capturing target bacteria, light was converted to heat signal by infrared irradiation. Moreover, the specific detection of S. aureus was realized by detecting the temperature change of the complex and the oxidation of TMB by nano-enzymes of residual CuS in the supernatant to form oxTMB blue product, which formed the change of UV (ultraviolet) − Visible spectroscopy. Based on the high specificity binding and strong signal amplification of the method, the linear range of the photothermal specific probe combined with MBs-S. aureus-CuS was 10–106 CFU/mL, and the detection limit was 1.407 CFU/mL. The linear range of the color specific probe was 10–106 CFU/mL, R2 = 0.9853, and the detection limit was 1.15 CFU/mL. The photothermal efficiency of MBs-S. aureus-CuS system can reach 62.84 %, which has excellent photothermal conversion effect, and the temperature rises to about 70 °C within 7 min, which can directly kill bacteria in the detection. In addition, the portable infrared thermal imager is applied to realize the real-time field detection of S. aureus. The study was significant, because exploratory experiments were conducted to conceive a proof-of-concept based on multiple bacterial sensors that could easily be adapted to a variety of fields where bacteria pose a threat.