Xiaoyi Tang,1,2,* Yijia Liu,1,2,* Mengxin Zhao,3,* Lei He,3 Jiahao Guo,3 Tian Wang,3 Wei Li,3 Jiaqi Zhao1 

1Department of Ultrasound, Shanghai Fourth People’s Hospital, School of Medicine, Tongji University, Shanghai, 200434, People’s Republic of China; 2Department of Ultrasound, the Second Affiliated Hospital of Naval Medical University (Shanghai Changzheng Hospital), Shanghai, 200003, People’s Republic of China; 3Department of Nanomedicine, Naval Medical University, Shanghai & School of Health Science and Engineering, University of Shanghai for Science and Technology, Shanghai, 200433, People’s Republic of China

*These authors contributed equally to this work

Correspondence: Wei Li; Jiaqi Zhao, Email liwei@smmu.edu.cn; ultrasoundczzjq@163.com

Purpose: This study aims to broaden the application of nano-contrast agents (NCAs) within the realm of the musculoskeletal system. It aims to introduce novel methods, strategies, and insights for the clinical management of ischemic muscle disorders, encompassing diagnosis, monitoring, evaluation, and therapeutic intervention.
Methods: We developed a composite encapsulation technique employing O-carboxymethyl chitosan (OCMC) and liposome to encapsulate NCA-containing gold nanorods (GNRs) and perfluoropentane (PFP). This nanoscale contrast agent was thoroughly characterized for its basic physicochemical properties and performance. Its capabilities for in vivo and in vitro ultrasound imaging and photothermal imaging were authenticated, alongside a comprehensive biocompatibility assessment to ascertain its effects on microcirculatory perfusion in skeletal muscle using a murine model of hindlimb ischemia, and its potential to augment blood flow and facilitate recovery.
Results: The engineered GNR@OCMC-liposome/PFP nanostructure exhibited an average size of 203.18± 1.49 nm, characterized by size uniformity, regular morphology, and a good biocompatibility profile. In vitro assessments revealed NCA’s potent photothermal response and its transformation into microbubbles (MBs) under near-infrared (NIR) irradiation, thereby enhancing ultrasonographic visibility. Animal studies demonstrated the nanostructure’s efficacy in photothermal imaging at ischemic loci in mouse hindlimbs, where NIR irradiation induced rapid temperature increases and significantly increased blood circulation.
Conclusion: The dual-modal ultrasound/photothermal NCA, encapsulating GNR and PFP within a composite shell-core architecture, was synthesized successfully. It demonstrated exceptional stability, biocompatibility, and phase transition efficiency. Importantly, it facilitates the encapsulation of PFP, enabling both enhanced ultrasound imaging and photothermal imaging following NIR light exposure. This advancement provides a critical step towards the integrated diagnosis and treatment of ischemic muscle diseases, signifying a pivotal development in nanomedicine for musculoskeletal therapeutics.

Keywords: ultrasonography, nanoscale contrast agent, nanotechnology, musculoskeletal ultrasound, photothermal imaging, microcirculatory perfusion