Study On Ultrasonic And Fluorescence Molecular Imaging Of Gold Nanoparticles Targeting Fibrosis

Objectives:As excellent functional materials,gold nanoparticles(Gold nanoparticles,AuNPs)have the advantages of controllable size,easy synthesis,easy surface modification,stable physical and chemical properties,safety and non-toxicity,so they have been widely used in the field of biomedical science,providing new technical methods for medical imaging diagnosis.Renal fibrosis is a common way of tissue remodeling in most chronic kidney diseases.At present,biopsy is the only method that can be used for the diagnosis and staging of renal fibrosis,but it has some limitations,so there is an urgent need to develop a non-invasive and rapid method that allows longitudinal segmentation to monitor the progress of renal fibrosis.Studies have shown that the process of renal fibrosis is accompanied by a series of pathophysiological processes such as angiogenesis,inflammation and so on.The expression of integrin αvβ3 receptor increased in endothelial cells during angiogenesis.RGD peptides have been widely used in molecular studies for the recognition of integrins.In this study,on the basis of glutathione(Glutathione,GSH)modified small photoluminescent gold nanoparticles(GSH-AuNPs),we constructed a targeted integrin αvβ3 receptor gold nanoparticles(GR-AuNPs)combined with RGD peptides,and preliminarily discussed the possibility of specially modified gold nanoparticles as ultrasound/fluorescence bimodal imaging contrast agents.To explore the relationship between targeted enhanced images of gold nanoparticles and renal fibrosis in mice,and to provide a new and practical method for non-invasive diagnosis and monitoring of renal fibrosis.Context(1)GSH-AuNPs and GR-AuNPs,were prepared by chemical reduction method.The physical properties were characterized by perspective electron microscope(TEM)and UV-visible spectrophotometer(UV-vis).(2)The safety and compatibility of the material was verified by the cell activity of HK-2 cells and HE staining of kidney tissue.(3)The model of renal fibrosis was established by intraperitoneal injection of folic acid(FA).The model was successfully established by HE staining and Masson staining,and the expression of integrin αvβ3 receptor was verified by immunohistochemistry.(4)GSH-AuNPs and GR-AuNPs were injected into the model mice through the tail vein as the model group,and the normal mice as the blank control group.The in vivo fluorescence imaging was performed by fluorescence imager and the kidney images were collected by high resolution animal ultrasound system,respectively,and the time-intensity changes were compared.At the same time,the kidney tissue was taken for pathological staining to verify the targeting of the material.Result(1)The average particle size of the prepared GSH-AuNPs is 1.7 nm.The average size of the GR-AuNPs AuNPs is 2 nm,and the maximum fluorescence emission peak of both of them is about 800nm.(2)The cell activity of HK-2 cells co-cultured with GSH-AuNPs and GR-AuNPs was more than 95%.The renal HE staining of the two groups showed that the renal structure was intact and there was no inflammatory damage.(3)The levels of serum creatinine,blood urea nitrogen and the expression of integrin αvβ3 in the renal fibrosis model group made by intraperitoneal injection of folic acid(FA)were significantly higher than those in the blank control group.(4)After injection of GR-AuNPs through caudal vein,the ultrasound and fluorescence imaging intensity of kidney in fibrosis model group gradually increased with time,and reached the peak value of 80min(P<0.001),and then decreased gradually,until 200min was significantly decreased(P<0.001).However,there was no significant change in renal imaging intensity of renal fibrosis group and blank control group(P>0.001).Combined with pathological silver staining,it was proved that GR-AuNPs was concentrated in fibrotic tissue.ConclusionThe self-made small size gold nanoparticles modified by RGD peptides can specifically target integrin αvβ3 receptor,enhance the ultrasonic echo intensity after local aggregation,and have the characteristic of fluorescence imaging,so it is expected to become a new molecular imaging contrast agent to realize ultrasound/fluorescence bimodal imaging of early renal fibrosis.