Novel Ultrasonic Imaging Probe For Tumor Microenvironment Imaging

Tumor microenvironment（TME）plays an important role in tumor growth,metastasis and invasion.Therefore,effective monitoring of TME is an effective means for tumor prediction.Ultrasonic（US）imaging is a relatively safe,convenient and low-cost imaging technology.With the help of US imaging probes,qualitative and quantitative studies at the cellular and molecular level in vivo can be realized.However,most of the commonly used clinical US probes are microbubbles,which not only have the risk of rupture at the clinical US frequency,but also are too large（usually at the microscale）to pass through the tumor vessel wall to reach the tumor tissue for detection.Comparatively,intelligent nano-US imaging probes could pass through tumor blood vessels and be enriched in tumor tissues through Enhanced Permeability and long Retention effect（EPR）.With intelligent structural design and component regulation,it is expected to be used for diagnosing TME accurately by US.Based on the above mention,two intelligent US molecular imaging nanoprobes are designed and prepared in this dissertation for diagnosing TME,mainly including the following two aspects:1.A new strategy based on“acoustic impedance difference self-enhancement"of materials for accurate detection of acidic TME:In view of the defects that clinical microbubbles（Sono Vue）can not enter the tumor tissues and are interfered by external pressure,which leads to its inability to diagnose TME.A novel strategy,based on“acoustic impedance difference self-enhancement”of materials,is proposed to monitor the acidic TME.Firstly,as US imaging probes,Bi F₃@PDA@PEG is designed and prepared.Bi F₃@PDA@PEG can self-aggregate in a specific response to the acidic TME,which improves tumor density locally and the acoustic impedance difference between tumor and the surrounding tissues.This results in the US signal change and realizes the sensitive detection of acidic TME.In vivo experiments show that the enhanced contrast extent was 6 times higher than pre,which is beneficial to detect the acidic TME.More importantly,compared with Sono Vue,BiF₃@PDA@PEG is stable and accurate in detecting acidic TME,independent of external pressure and other factors.The strategy not only realizes the accurate detection of the acidic TME,but also provides an important guidance to detect other microenvironments,not limited to tumors,by utilizing US imaging.2.A new Fe-based US imaging probe for precise detection of Casp3 in TME:Casp3,a kind of apoptotic enzymes,plays a key role in cell apoptosis.However,the accurate detection of Casp3 can not be realized by US imaging.Therefore,this work prepares intelligent nanoprobe,Fe₃O₄@1,by covalence of Ac-Asp-Glu-Val-Asp-Cys（St Bu）-Lys-CBT（1）and Fe₃O₄NPs.The Fe₃O₄@1 nanoprobe realizes the accurate detection of Casp3 by using US imaging.Fe₃O₄@1 can specifically respond to the apoptotic enzyme Casp3,and undergo condensation reaction to yield cross-linked Fe₃O₄NPs aggregations.This cross-linked Fe₃O₄NPs can enhance the density difference and acoustic impedance difference between tumor tissues and nearby tissues.By using US imaging,the accurate detection of Casp3 in tumor area is realized.This strategy further expands the scope of the application of US imaging and provides a new idea for the precise detection of the TME and other diseases by using US imaging technique.