Cationic polyelectrolyte functionalized magnetic particles assisted highly sensitive pathogens detection in combination with polymerase chain reaction and capillary electrophoresis

• We prepared PDDA-MPs by three reaction steps.
• Bacteria were captured by PDDA-MPs based on electrostatic interactions between them.
• A PDDA-MPs-PCR-CE method was developed for sensitive detection of bacteria.
• Trace amount of bacteria at 101 cfu mL−1 was detected.

Pathogenic bacteria cause significant morbidity and mortality to humans. There is a pressing need to establish a simple and reliable method to detect them. Herein, we show that magnetic particles (MPs) can be functionalized by poly(diallyl dimethylammonium chloride) (PDDA), and the particles (PDDA-MPs) can be utilized as adsorbents for capture of pathogenic bacteria from aqueous solution based on electrostatic interaction. The as-prepared PDDA-MPs were characterized by Fourier-transform infrared spectroscopy, zeta potential, vibrating sample magnetometry, X-ray diffraction spectrometry, scanning electron microscopy, and transmission electron microscopy. The adsorption equilibrium time can be achieved in 3 min. According to the Langmuir adsorption isotherm, the maximum adsorption capacities for E. coli O157:H7 (Gram-negative bacteria) and L. monocytogenes (Gram-positive bacteria) were calculated to be 1.8 × 109 and 3.1 × 109 cfu mg−1, respectively. The bacteria in spiked mineral water (1000 mL) can be completely captured when applying 50 mg of PDDA-MPs and an adsorption time of 5 min. In addition, PDDA-MPs-based magnetic separation method in combination with polymerase chain reaction and capillary electrophoresis allows for rapid detection of 101 cfu mL−1 bacteria.