In vivo targeted fluorescence imaging and magnetic resonance imaging of E. coli bacterial infection using polymyxin B-conjugated and polyacrylic acid-grafted GdEuO3 nanoparticles.

Lanthanide oxide nanoparticles are ideal systems for highly sensitive diagnosis of infectious diseases because of their excellent optical, magnetic, and physicochemical properties. In this study, polymyxin B (PMB), serving as an E. coli-targeting ligand, was conjugated with polyacrylic acid (PAA)-grafted GdEuO3 nanoparticles, used as Eu-based fluorescence imaging (FI) and Gd-based magnetic resonance imaging (MRI) agents. The PMB-PAA-GdEuO3 nanoparticles were further conjugated with the organic photosensitizer 2,6-pyridinedicarboxylic acid (PDA) to enhance their Eu photoluminescence in the visible region (i.e., red color). The performance of (PMB-PAA)/PDA-GdEuO3 nanoparticles as E. coli-targeting and detection agents was demonstrated in vivo on an E. coli-infected mouse model using FI and MRI.