Molecular Imaging Study On The Preparation Of Targeted Nanometer Contrast Agents To Evaluate The Efficacy Of Ablation

ObjectivesThermal ablation has been widely used in minimally invasive treatment of tumors,however,incomplete ablation might accelerate tumor progression.Due to the blur or irregular boundary of tumor,it is difficult to accurately estimate the boundary of the ablation zone.Therefore,accurate evaluation by contrast enhanced ultrasound(CEUS)plays a key role in the ablation.The application of nano-targeted ultrasound contrast agent(UCA)could target and locate tumor tissues accurately.The purpose of this study was to evaluate the changes of proliferation and invasion ability of breast cancer cells with sublethal heat.A novel UCA VEGFR2-targeting iron-doped silica(Si O₂)hollow nanosphere was made to evaluate its physicochemical properties and safety.It was applied in microwave ablation for breast cancer xenograft to investigate its value in the evaluation of effectiveness after ablation.MethodsIn vitro thermal ablation models of breast cancer were established by using cell and molecular biology and animal models to observe the changes of cell proliferation and invasion ability under the stimulation of sublethal heat.Proteomics information related to sublethal heat stimuli was obtained by using label free proteomics.VEGFR2-PEG-HSNs-Fe was prepared by using nano-Si O₂,which was regarded as a substrate and etched by Ferrous acetate,and then modified with targeted VEGFR2antibody.The nanometer particle size potential analyzer and laser confocal microscope were used to observe its main physicochemical properties,and we also evaluated its specific targeting ability in vitro qualitatively and quantitatively.The biological safety was investigated in vitro and in vivo by flow cytometry,biological behavior observation,blood biochemical index,serum immune index and pathological examination of organs.Ultrasound was used to evaluate the quality of imaging.After the xenograft tumor of 4T1cells was treated by microwave ablation,the extent of perfusion defect was evaluated by injecting different UCAs.ResultsThe temperature 45? was a sublethal temperature of 4T1 cells,which could enhance the ability of proliferation and invasion.Heat shock protein 1B,NOB1 and CRIP1 increased after stimulation at 45?,while BCLAF1 decreased.The average particle size of VEGFR2-PEG-HSNs-Fe was 276.64±30.31 nm,and the surface potential was-13.46±2.83 m V.In vitro,the intensity of ultrasound signal increased with UCA concentration.VEGFR2-PEG-HSNs-Fe can combine with human umbilical vein endothelial cells with a binding rate of 74.80±2.21%.With the increase of UCA concentration,the cell survival rate decreased gradually,but kept at about 80%or above.In vivo,after injecting VEGFR2-PEG-HSNs-Fe,no abnormal biological behaviors were observed in the mice.The main blood cells,biochemical and immune indicators were within normal range,and the structure of main organs was normal.Enhanced ultrasound signal was detected in the tumor after injecting VEGFR2-PEG-HSNs-Fe,covering the whole tumor.After ablation,tumor residue was detected by injecting VEGFR2-PEG-HSNs-Fe.The lesions,which were incompletely ablated,showed contrast agent perfusion at the periphery of the tumor.After complementary ablations,there was no perfusion in the ablated zone,and complete ablation was achieved in all cases.Compared with conventional UCA,less time was required for ablation by using VEGFR2-PEG-HSNs-Fe.ConclusionDuring incomplete ablation,the stimulation of sublethal heat could promote the proliferation and invasion of breast cancer.Nano-targeted UCA VEGFR2-PEG-HSNs-Fe has good biosafety and ability of specific imaging,which might be helpful to evaluate the efficacy of tumor ablation and avoid incomplete ablation.