Rapid Legionella pneumophila determination based on a disposable core–shell Fe3O4@poly(dopamine) magnetic nanoparticles immunoplatform

•A novel amperometric immunosensor for determination of L. pneumophila is presented.•Capture antibody was linked to the poly(dopamine)–modified magnetic nanoparticles.•Bacteria were sandwiched using the antibody labeled with horseradish peroxidase.•The method showed a good selectivity and modified–MNPs good stability during 30 days.

A novel amperometric magnetoimmunoassay, based on the use of core–shell magnetic nanoparticles and screen-printed carbon electrodes, was developed for the selective determination of Legionella pneumophila SG1. A specific capture antibody (Ab) was linked to the poly(dopamine)–modified magnetic nanoparticles (MNPs@pDA-Ab) and incubated with bacteria. The captured bacteria were sandwiched using the antibody labeled with horseradish peroxidase (Ab-HRP), and the resulting MNPs@pDA-Ab-Legionella neumophila-Ab-HRP were captured by a magnetic field on the electrode surface. The amperometric response measured at −0.15 V vs. Ag pseudo-reference electrode of the SPCE after the addition of H2O2 in the presence of hydroquinone (HQ) was used as transduction signal. The achieved limit of detection, without pre-concentration or pre-enrichment steps, was 104 Colony Forming Units (CFUs) mL−1. The method showed a good selectivity and the MNPs@pDA-Ab exhibited a good stability during 30 days. The possibility of detecting L. pneumophila at 10 CFU mL−1 level in less than 3 h, after performing a membrane-based preconcentration step, was also demonstrated.

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