Optical/MRI dual-modality imaging of M1 macrophage polarization in atherosclerotic plaque with MARCO-targeted upconversion luminescence probe.

Pro-inflammatory M1 macrophage is identified as a prominent component initializing the progress of vulnerable atherosclerotic plaque. Here, we constructed anti-MARCO NaGdF:Yb,Er@NaGdF upconversion nanoparticles (UCNPs) by conjugating polyclonal MARCO antibody to the surface of NaGdF:Yb,Er@NaGdFvia condensation reaction. UCNPs displayed highly mono-dispersion with average sizes of 26.7 ± 0.8 nm and favorable biocompatibility. In vivo upconversion optical imaging revealed that distinctive fluorescence signal could be observed in the regions of carotid artery 10 min post-injection, reached peak value at 1 h and decreased back to baseline at 24 h post-injection. The carotid artery wall demonstrated high signal intensity on T1-weighted MR images after anti-MARCO UCNPs injection, as determined by 7.0T MRI. Immunofluorescence staining of tissue section of carotid artery revealed that MARCO was highly abundant in shoulder regions of plaque. Anti-MARCO UCNPs is a promising optical/MRI dual-modality imaging probe which can non-invasively reflect M1 phenotype macrophages behavior in vivo.