Fluorescence Imaging of Foamy Macrophages by Scavenger Receptor-AI (SR-AI) Targeted Quantum Dots

Objective: Foamy macrophages are playing a critical role in atherosclerotic plaque initiation, formation and rupture. Here, to sensitively and selectively imaging the atherosclerotic plaque, we reported imaging probe QDs@BSA@PP1, which could specifically integrate with special receptors scavenger receptor-AI (SR-AI) over-expressed on foamy macrophages during their formation stage. Methods: Fluorescence imaging component quantum dot (CdSe/CdS/CdxZn(1-x)S/ZnS QDs) were firstly synthesized and modified by bovine serum albumin (BSA) encapsulation. After covalent coupling of PP1, the final imaging probe was formed. The RAW264.7 macrophages were utilized to form foam cells and conducted by real-time PCR and Oil-red O staining. MTT assay was performed to evaluate the cytotoxicity of the QDs@BSA@PP1. Qualitative assessment of binding/uptake of PP1 by macrophage-derived foam cells (macrophages with ox-LDL treated) and low SR-AI-expressed macrophage cells (without ox-LDL treated), which were incubated with PBS (control), free PP1, free QDs, QDs@BSA@PP1 and QDs@BSA@PP1&PP1, and observed by fluorescence microscope. Results: The fluorescence imaging probe could efficiently locate on the membrane and the cytoplasm of foam cells, expressing intensive red fluorescent signal. At the same time, foam cells incubated with QDs@BSA only exhibited relatively weak red fluorescence. Conclusions: Collectively, QDs@BSA@PP1 has been proved as a promising molecular probe with excellent biocompatibility, allowing the fluorescence imaging of SR-AI over-expressed macrophage-derived foam cells, which was promising for future precise detection of vulnerable plaques.