Luminescence-Resonance-Energy-Transfer-Based Luminescence Nanoprobe for In Situ Imaging of CD36 Activation and CD36–oxLDL Binding in Atherogenesis

Macrophage foam cell formation mediated by CD36 receptor dependent internalization of oxidized low-density lipoprotein (oxLDL) is an important hallmark of early atherosclerosis. Activation of CD36 and its binding to oxLDL are the key points in foam cell formation. Herein, we develop a site-specific luminescence resonance energy transfer (LRET) system for the simultaneous imaging of CD36 activity and CD36-oxLDL binding on the cell surface. The system utilizes CD36-antibody-modified, SiO2-coated upconversion luminescent nanoparticles (UCNPs) as an energy donor to target the plasma membranes of macrophages, and DiI-oxLDL (energy acceptor) binds to CD36 and passes through the membrane during macrophage foam cell formation. Upon excitation at 980 nm, the LRET signal can be obtained because of the short distance between DiI-oxLDL and the nanoprobe. Additionally, the very specific fluorescence can be used to visualize distinct features of CD36. The nanoprobe also exhibits high sensitivity, good stability, simplicity, and low cost for the accurate detection and evaluation of macrophage foam cell formation. Moreover, using this novel nanoprobe, we also investigate the mechanism by which reactive oxygen species (ROS) signaling enhances the binding of oxLDL to CD36. ROS, especially O2·-, alter endothelial permeability and facilitate CD36 clustering, ultimately promoting the entry and internalization of oxLDL. Because of these advantages, this nanoprobe may provide a versatile platform for monitoring the progression of atherogenesis and elucidating atherogenesis signaling at the cellular level.