Magnet-Guided Bionic System with LIFU Responsiveness and Natural Thrombus Tropism for Enhanced Thrombus-Targeting Ability

Ni Fang,1,2,* Jia Liu,1,* Jingxin Hou,1,2 Yixin Zhong,1,2 Ying Luo,1,2 Liu Hu,1,2 Wenli Zhang,1,2 Junrui Wang,1,2 Jie Xu,1 Jun Zhou,1 Yu Zhang,1 Haitao Ran,2 Dajing Guo1 1Department of Radiology, Second Affiliated Hospital of Chongqing Medical University, Chongqing, 400010, People’s Republic of China; 2Chongqing Key Laboratory of Ultrasound Molecular Imaging & Department of Ultrasound, Second Affiliated Hospital of Chongqing Medical University, Chongqing, 400010, People’s Republic of China*These authors contributed equally to this workCorrespondence: Dajing Guo, Email guodaj@163.comBackground: Arterial thrombosis is a serious threat to human health. Recently, many thrombus-targeted nanoparticles (NPs) have been constructed for detecting thrombi or monitoring thrombolysis, but their thrombus-targeting performance is limited. Considering this drawback, we designed a specific bionic system with enhanced thrombus-targeting ability.Materials and Methods: In the bionic system, gelatin was chosen as a carrier, and Fe3O4 served as a magnetic navigation medium and a magnetic resonance (MR) imaging agent. The CREKA peptide, which targets fibrin, was conjugated to the surface of gelatin to prepare targeted NPs (TNPs), which were then engulfed by macrophages to construct the bionic system. At the targeted site, the bionic system released its interior TNPs under low-intensity focused ultrasound (LIFU) irradiation. Moreover, the targeting performance was further improved by the conjugated CREKA peptide.Results: In this study, we successfully constructed a bionic system and demonstrated its targeting ability in vitro and in vivo. The results indicated that most TNPs were released from macrophages under LIFU irradiation at 2 W/cm2 for 10 min in vitro. Additionally, the enhanced thrombus-targeting ability, based on the natural tropism of macrophages toward inflammatory thrombi, magnetic navigation and the CREKA peptide, was verified ex vivo and in vivo. Moreover, compared with the bionic system group, the group treated with TNPs had significantly decreased liver and spleen signals in MR images and significantly enhanced liver and spleen signals in fluorescence images, indicating that the bionic system is less likely to be cleared by the reticuloendothelial system (RES) than TNPs, which may promote the accumulation of the bionic system at the site of the thrombus.Conclusion: These results suggest that the magnet-guided bionic system with LIFU responsiveness is an excellent candidate for targeting thrombi and holds promise as an innovative drug delivery system for thrombolytic therapy.Keywords: bionic system, low-intensity focused ultrasound, thrombus, magnetic navigation, macrophage