| Purpose:Early and accurate visualization and diagnosis of vulnerable atherosclerotic plaques is extremely critical for prevention and treatment of acute cardiovascular and cerebrovascular diseases.However,the limitations of inadequate targeting specificity and imaging sensitivity seriously hinder their development and greatly increased the sufferings and economic bear of patients.In order to solve the problems above,a novel dual-modality imaging nanoprobe with high-resolution imaging and highly specific targeting was established for early noninvasive and accurate detection of vulnerable plaque characteristics in this study.Methods:Here,we aim to utilize the over-expressed scavenger receptors-AI（SR-AI）as a target,employ the gadolinium-functionalized gold nanoclusters（NCs）as the carrier to construct a high-performing magnetic resonance（MR）/fluorescence dual-modality molecular imaging probe（PP1-Au@GSH@Gd NCs）for the precise assessment of vulnerable plaques.Then we characterize the properties,biocompatibility and in vivo biodistribution of the probe.The murine macrophage cell lines（RAW264.7）were cultured for in vitro cellular imaging,and the atherosclerosis model was induced in ApoE-/-mice by high-fat diet.Then in vivo MRI and fluorescence imaging of ApoE-/-mice were carried out to evaluate the plaque burden and characteristics.Ultimately,histopathological quantitative analysis was performed to confirm the probe accumulation.Results:（1）The fabricated PP1-Au@GSH@Gd NCs possessed uniform size and superior dispersity.The hydrodynamic diameter was about 6.1±0.12 nm and theζ-potential was-10.3±2.48 m V.They had excellent colloid stability,and the UV-vis absorption spectra showed characteristic absorbance peak at 400 nm.（2）The PP1-Au@GSH@Gd NCs demonstrated an extremely high T1 relaxivity of 28.347 mM-1·s-1 and possessed both remarkable T1-weighted MR imaging capacity and admirable fluorescence imaging capabilities.Negligible cytotoxicity and favorable biocompatibility were confirmed by MTT assays,in vivo biochemical analysis and body weight monitoring,which demonstrated PP1-Au@GSH@Gd NCs could be an ideal contrast agent for plaque dual-modality imaging.（3）To validate targeting efficiency,RAW264.7 macrophages were cultured,and in vitro binding experiments were performed through laser confocal imaging,flow cytometry and MR imaging.All of these data indicated high binding specificity and affinity of PP1-Au@GSH@Gd NCs to the foam macrophages in a SR-AI dependent manner.（4）After being fed with high fat and cholesterol diet（HFD）for 20 weeks,body weighting,serum lipid profiles,and Oil Red O staining of arteries were carried out to verify the successful establishment of ApoE-/-mice models of vulnerable plaques.（5）In vivo MR/fluorescence dual-modality molecular imaging of plaques in ApoE-/-mice exhibited pronounced plaque enhancements after the PP1-Au@GSH@Gd NCs injection.Over time,the signal enhancements of vulnerable plaques became increasingly apparent within 8 h,and they could last up to 32 h.（6）Subsequent histologic examinations including silver-staining,Oil Red O staining,immunofluorescence staining and immunohistochemical staining for SR-AI and F4/80 further confirmed that the PP1-Au@GSH@Gd NCs indeed accumulated in SR-AI over-expressed vulnerable plaque regions.Conclusion:The PP1-Au@GSH@Gd NCs we constructed could precisely target the rupture-prone vulnerable plaques and provide pathological information about the molecular signatures and plaque compositions from multiple perspectives.These data provide experimental evidence and important scientific basis for early accurate diagnosis and noninvasive monitoring of vulnerable plaques,and have a broad application prospects in the clinical practice of atherosclerosis. |
