Magnetic–optical nanohybrid for targeted detection, separation, and photothermal ablation of drug-resistant pathogens

A rapid, sensitive and quantitative immunoassay for the targeted detection and decontamination of E. coli based on Fe 3 O 4 magnetic nanoparticles (MNPs) and plasmonic popcorn-shaped gold nanostructures attached single-walled carbon nanotubes (AuNP@SWCNT) is presented. The MNPs were synthesized as the support for the monoclonal antibody (mAb@MNP). E. coli (49979) was captured and rapidly preconcentrated from sample with the mAb@MNP, followed by binding with Raman-tagged concanavalin A-AuNP@SWCNT (Con A-AuNP@SWCNT) as detector nanoprobes. A Raman tag 5,5'-dithiobis-(2-nitrobenzoic acid) (DTNB) generated Raman signal upon 670 nm Laser excitation enabling detection and quantification of E. coli concentration with a limit of detection of 10 2 CFU/mL and a linear logarithmic response range of 1.0 × 10 2 to 1.0 × 10 7 CFU/mL. The mAb@MNP could remove more than 98% of E. coli (initial concentration of 1.3 × 10 4 CFU/mL) from water. The potential of the immunoassay to detect E. coli bacteria in real water samples was investigated and the results were compared with the experimental results from classical count method. There was no statistically significant difference between the two methods (p > 0.05). Furthermore, the MNP/AuNP@SWCNT hybrid system exhibits enhanced photothermal killing effect. The sandwich-like immunoassay possesses the potential for rapid bioanalysis and simultaneous biosensing of multiple pathogenic agents.