Sensitive detection of Listeria monocytogenes based on highly efficient enrichment with vancomycin-conjugated brush-like magnetic nano-platforms

Pathogens pose a significant threat to public health worldwide. Despite many technological advances in the rapid diagnosis of pathogens, sensitive pathogen detection remains challenging because target pathogenic bacteria usually exist in complex samples at very low concentrations. Here, the construction of multivalent brush-like magnetic nanoprobes and their application for the efficient enriching of pathogens are demonstrated. Brush-like magnetic nanoprobes were constructed by modification with poly-L-lysine (PLL) onto amino-modified magnetic beads, followed by coupling of PEG (amine-PEG5000-COOH) to the amine sites of PLL. Subsequently, vancomycin (Van), a small-molecule antibiotic with affinity to the terminal peptide (D-alanyl-D-alanine) on the cell wall of Gram-positive bacteria, was conjugated to the carboxyl of the PEG. The use of multivalent brush-like magnetic nanoprobes (Van-PEG-PLL-MNPs) results in a high enrichment efficiency (>94%) and satisfactory purity for Listeria monocytogenes (employed as a model) within 20 min, even at bacterial concentrations of only 102 cfu mL-1. Integrated with the enrichment of the Van-PEG-PLL-MNP nano-platform and electrochemiluminescence (ECL) detection, Listeria monocytogenes can be rapidly and accurately detected at levels as low as 10 cfu mL-1. The approach described herein holds great potential for realizing rapid and sensitive pathogen detection in clinical samples.