NIR-II\nImaging for Tracking the Spatiotemporal Immune\nMicroenvironment in Atherosclerotic Plaques

The\ninflammatory immune microenvironment is responsible for atherosclerotic\nplaque erosion and rupture. Near-infrared-II (NIR-II) fluorescence\nimaging has the potential to continuously monitor the spatiotemporal\nchanges in the plaque immune microenvironment. Herein, we constructed\nthree different NIR-II probes based on benzo[1,2-<i>c</i>;4,5-<i>c</i>’]bis[1,2,5]thiadiazole-4,7-bis(9,9-dioctyl-9<i>H</i>-fluoren-2-yl)thiophene (denoted as BBT-2FT): VHPK/BBT-2FT\nNPs, where VHPK is a specific peptide targeting vascular cell adhesion\nmolecule-1; iNOS/BBT-2FT NPs for modulating the polarization of M1\nmacrophages by inducible NO synthase (iNOS) antibodies; and Arg-1/BBT-2FT\nfor counterbalancing the inflammatory responses of M1 macrophages.\nThese tracers enable precise tracking of atherosclerotic plaques and\nM1 and M2 macrophages through NIR-II imaging. VHPK/BBT-2FT NPs can\naccurately trace atherosclerotic plaques at various stages. Arg-1/BBT-2FT\nNPs precisely located M2 macrophages in the early plaque microenvironment\nwith upregulation of peroxisome proliferator-activated receptor γ\n(PPAR-γ), signal transducer and activator of transcription (STAT)\n6, and ATP-binding cassette transporter A1 (ABCA1), indicating that\nM2 macrophage polarization is crucial for early plaque lipid clearance.\nMeanwhile, iNOS/BBT-2FT NPs accurately tracked M1 macrophages in the\nadvanced plaque microenvironment. The results showed that M1 macrophage\npolarization induces the formation of an inflammatory microenvironment\nthrough anaerobic glycolytic metabolism and pyroptosis in the advanced\nhypoxic plaque microenvironment, as indicated by the upregulation\nof hypoxia-inducible factor 1 alpha (HIF-1α), STAT1, NOD-, LRR-,\nand pyrin domain-containing protein 3 (NLRP3), pyruvate dehydrogenase\nkinase 1 (PDK1), and glucose transporter 1 (GLUT-1). Combining immunological\napproaches with NIR-II imaging has revealed that hypoxia-induced metabolic\nreprogramming of macrophages is a key factor in dynamic changes in\nthe immune microenvironment of atherosclerotic plaques. Furthermore,\nour strategy shows the potential for real-time diagnosis and clinical\nprevention of unstable plaque rupture in atherosclerosis.