Ultrasound Molecular Imaging Of Myocardial Fibrosis Using CNA35 Collagen-Targeted Fluorocarbon Nanoparticles

PART ? ESTABLISHMENT OF FIBROSIS MODELING AFTER ACUTE MYOCARDIAL INFARCTION IN RABBITSObjective To establish a model of myocardial infarction fibrosis in New Zealand white rabbits,and to determine whether the model was successful by comparing the preoperative and postoperative electrocardiogram changes and subsequent pathological sections for collagen staining.Methods The same batch of New Zealand white rabbits was randomly selected.After anesthesia,the left anterior descending coronary artery(LAD)was ligated to establish the model of acute myocardial infarction(MI)model.After one month of feeding,the myocardial tissue was taken to make pathological section and collagen staining was performed.Results Postoperative electrocardiogram V1 lead showed that the ST segment was significantly elevated in the arch back,and the distal myocardium of the ligation is bluish purple,which proved that the rabbit model of acute myocardial infarction was successfully established.HE staining and collagen staining of the myocardial tissue one month after surgery confirmed the success of the myocardial infarction model,which showed that the myocardial tissue in the infarction area was replaced by collagen fibers.Conclusions The fibrosis model of rabbits with acute myocardial infarction can be successfully established by ligation of the anterior descending coronary artery.PART ? THE STUDY OF COLLAGEN TARGETING IN VIVO OF CNA35 COLLAGEN TARGETED FLUOROCARBON NANOPARTICLESObjective To prepare a novel liquid-gas phase ultrasonic probe(CNA35-PFP NPs)mediated by CNA35 and evaluate its targeting in vivo.Methods Lipid nanoparticles containing liquid fluorocarbon(PFP NPs-Di I)were prepared by membrane-hydration and acoustic-vibration methods.CNA35-FITC-PFP NPs-Di I was successfully synthesized by the carbodiimide method.The same batch of acute myocardial infarction fibrosis model rabbits and normal rabbits were randomly selected.After anesthesia,diluted PFP NPs-Di I and CNA35-FITC-PFP NPs-Di I(2 m L/kg)were injected through the ear vein,and the corresponding site tissues were removed after 1 h in the dark to prepare frozen sections.And nuclear localization was performed by DAPI staining,and qualitatively observed under a fluorescence confocal microscope.Results After injection of CNA35-FITC-PFP NPs-Di I,green fluorescent collagen fibers and red fluorescent lipid nanoparticles were observed under fluorescence confocal microscopy in the acute myocardial infarction model group,while the other three groups were failed to observe.Conclusion CNA35 collagen-targeted fluorocarbon nanoparticles(CNA35-PFP NPs)can effectively bind to myocardial fibrosis in vivo,confirming that CNA35-PFP NPs can pass through the vascular endothelium and can specifically bind to type I collagen in fibrotic myocardial tissue,laid the foundation for subsequent experiments.PART ? ULTRASOUND MOLECULAR IMAGING STUDY OF CNA35 COLLAGEN-TARGETED FLUOROCARBON NANOPARTICLES FOR DETECTION OF MYOCARDIAL FIBROSISObjective To prepare a novel liquid-gas phase transition ultrasound molecular probe(CNA35-PFP NPs)mediated by CNA35 and evaluate its effectiveness in detecting myocardial fibrosis.Methods The position of the apex was located in a two-dimensional(B type)mode using an ultrasonic diagnostic apparatus,and the shape of the heart was observed through the long axis and the short axis of the left ventricle to initially determine the location of the myocardial infarction.Myocardial thickness,motion,and echo intensity were observed in the post-infarction fibrosis model group by ultrasound.PFP NPs and CNA35-PFP NPs were injected intravenously through the ear margin.After 5 min,the data for each group were recorded for comparison.Then LIFU was used to focus the ultrasound radiation with 3W/cm2 power for 3 min,and the enhanced ultrasonograms before and after irradiation in the B-mode and contrast enhanced ultrasound(CEUS)mode were compared.Results In the acute infarction fibrosis model group,the myocardial thinning was observed in the anterior wall of the left ventricle and/or between the anterior wall or the anterior wall of the right ventricle in two-dimensional ultrasound mode(p<0.05),and the echo was enhanced(p<0.05),suggesting infarct site is located in the anterior wall and the anterior septum,and no enhancement of visualization is observed in the contrast-enhanced mode.In the CNA35-PFP NPs+LIFU group,the myocardial infarction area showed a significantly enhanced echo signal after LIFU irradiation(p<0.05),and the echo enhancement of post-infarction fibrosis was also observed in CEUS mode.But in the PFP NPs+LIFU group,echo enhancement of the infarcted area was not observed in the B-mode,and also was not observed in the CEUS mode.Conclusion NA35-PFP NPs can effectively pass through the vascular endothelium,target to the myocardial fibrosis site and specifically bind to type I collagen of fibrotic myocardium.After LIFU irradiation,the phase change enhances the ultrasound development of fibrotic myocardial tissue.However,PFP NPs lack targeting,unable to aggregate in fibrotic myocardium and enhance the development of fibrotic myocardium.