Rapid and direct MALDI-MS identification of pathogenic bacteria from blood using ionic liquid-modified magnetic...

A novel method for pathogenic bacteria identification directly from blood samples using cationic ionic liquid-modified magnetic nanoparticles (CILMS) is reported. The magnetic nanoparticles were prepared by co-precipitation and the core-shell Fe₃O₄@SiO₂ nanoparticles were prepared by the sol-gel process, followed by the grafting of 3-chloropropyltrimethoxysilane that was reacted further with N-methylimidazole to form cationic ionic liquid-modified Fe₃O₄@SiO₂ magnetic nanoparticles (CILMS). The pathogenic bacteria were separated mainly based on the electrostatic interactions among the negative charges of the cell membranes and the positive charges of the CILMS particles. CILMS are used directly without the need for any further apparatus and auxiliary chemicals. The separated cells were detected using matrix assisted laser desorption/ionization mass spectrometry (MALDI-MS). The lowest detectable number of bacteria was 3.4 × 10³, 3.2 × 10³, and 4.2 × 10³ cfu mL^-1 for Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus, respectively. The bacterial affinity toward CILMS was investigated using transmission electron microscopy which revealed immobilization of the CILMS on the outer cell membranes. The present approach offers a highly sensitive, fast, and simple method for the cell capture of the pathogenic bacteria. The current approach could be adapted to separate and identify the pathogenic bacteria from septicemic patients or contaminated blood before blood transfusion.