Lanthanide/CuSe Nanoparticles for Bacteria-Activated NIR-II Fluorescence Imaging of Infection.

A material system enabling specific NIR-II fluorescence imaging of Gram-positive bacteria is described. The material system is based on the electrostatic binding of CuSe and vancomycin-modified NaGdF:Nd,Yb@NaGdF downconversion nanoparticles (DCNPs), the fluorescence of which is weak owing to the spectral overlap of CuSe absorption with the DCNP NIR emission. The presence of Gram-positive bacteria precisely disconnects the bond between vancomycin-modified DCNPs and CuSe, thus enabling a strong fluorescent signal. studies show that the material system can be specifically activated at the site of Gram-positive bacterial infection but is essentially nonfluorescent in the area of Gram-negative bacterial infection.