NIR-II multiplexed fluorescence imaging of bacteria based on excitation-selective lanthanide-doped core-shell nanoparticles

Physiological processes and bacterial infection can be effectively monitored using multiplexed imaging in the second near-infrared region (NIR-II). In this study, we design two lanthanide-doped core-shell (cs) nanoparticles , NaYF 4 :Nd,Yb@NaYF 4 (csNd,Yb) with 980 and 1060 nm emission under 808 nm excitation, and NaYF 4 :Yb,Er,Ce@NaYF 4 (csYb,Er,Ce) with 1525 nm emission under 980 nm excitation. The NIR-II emission spectra of the two nanoparticles do not overlap. XRD characterization shows that the nanoparticles have good crystallinity . The nanoparticles are surface modified with vancomycin (Van) and polymyxin B (PMB), which can respectively target Gram-positive and Gram-negative bacteria for specific imaging and bacteria differentiation. In vitro experiments confirm that csNd,Yb-PMB and csYb,Er,Ce-Van can be used to detect different types of bacteria. In vivo simultaneous multiplexed NIR-II imaging of Gram-positive/negative bacterial infection is demonstrated. The good biocompatibility of the nanoprobes is demonstrated by MTT assay, monitoring the distribution in major organs at different times, and histological analysis .