Gold Nanorod-Loaded Nano-Contrast Agent with Composite Shell-Core Structure for Ultrasonic/Photothermal Imaging-Guided Therapy in Ischemic Muscle Disorders

Abstract

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

Abbreviations

APS, Ammonium persulfate; α-SMA, α-smooth muscle actin; CCK-8, Cell Counting Kit 8; CDFI, color Doppler flow imaging; CEUS, contrast-enhanced ultrasound; CTAB, cetyltrimethy-lammonium bromide; DMEM, Dulbecco’s modified Eagle’s medium; FBS, Fetal Bovine Serum; GNR, gold nanorod; H&E, haematoxylin and eosin; MB, microbubble; MMA, Methyl methacrylate; NCA, nano-contrast agent; NIR, near-infrared; NP, nanoparticle; nUCA, nanoscale ultrasound contrast agent; OCMC, O-carboxymethyl chitosan; ODV, optical droplet vaporization; PBS, Phosphate Buffered Saline; PDI, polydispersity index; PECAM-1, Platelet Endothelial Cell Adhesion Molecule-1; PFP, perfluoropentane; POPC, 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine; SPR, surface plasmon resonance; TEM, transmission electron microscopy; UCA, ultrasound contrast agent.

Acknowledgments

This research was sponsored by the National Natural Science Foundation of China (81501492), the Natural Science Foundation of Shanghai of China (20ZR1457900), Program of Shanghai Academic Research Leader (22XD1404700), the Three-year Action Plan of Talent Construction of Changzheng Hospital, Military Medical Talent Project of Pyramid Talent Project, Science and Technology Initiation Special Program of Shanghai Fourth People’s Hospital of Tongji University (SYKYQD06101), Medical Research Project of Shanghai Hongkou District Health Commission (2302-26) and Clinical Key Supporting Project of Health Commission of Shanghai Hongkou District (HKLCFC202404). The authors would like to express their gratitude to EditSprings (https://www.editsprings.cn) for the expert linguistic services provided.

Disclosure

The authors declare no conflicts of interest in this work.