Construction of Fe3O4/Vancomycin/PEG Magnetic Nanocarrier for Highly Efficient Pathogen Enrichment and Gene Sensing

Infectious diseases, especially pathogenic bacterial infections, pose a growing threat to public health worldwide. As pathogenic bacteria usually exist in complex experimental matrixes at very low concentrations, developing a technology for rapid and biocompatible sample enrichment is essential for sensitive diagnosis. In this study, an Fe3O4/Vancomycin/PEG magnetic nanocarrier was constructed for efficient sample enrichment and in situ nucleic acid preparation of pathogenic bacteria for subsequent gene sensing. We attached Vancomycin, a well-known broad-spectrum antibiotic, to the surface of Fe3O4 nanoparticles as a universal molecular probe to target bacterial cells. Polyethylene glycol (PEG) was introduced to enhance the nanocarrier's water solubility and biocompatibility. Results show that the proposed nanocarrier achieved a 90% capture efficiency even if at a Listeria monocytogenes concentration of 1×10(2) cfu/mL. Contributing to the good water solubility achieved by the employment of modified PEG, highly efficient enrichment (enrichment factor 10 times higher than PEG-free nanocarrier) can be completed in 30 min. Moreover, PEG would also develop the nanoparticles' biocompatibility by passivating the positively charged unreacted amines on the magnetic nanoparticles, thus helping to release the negatively charged bacterial genome from the nanocarrier/bacteria complexes when an in situ nucleic acids extraction step was executed. The outstanding bacterial capture capability and biocompatibility of this nanocarrier enabled the implementation of a highly sensitive gene-sensing strategy of pathogens. By employing an electrochemiluminescence-based gene-sensing assay, L. monocytogenes can be rapidly detected with a limit of detection of 10 cfu/mL, which shows great potential for clinical applications.