Prussian blue nanocubes as a multimodal contrast agent for image-guided stem cell therapy of the spinal cord

Translation of stem cell therapies to treat injuries and diseases of the spinal cord is hindered by lack of real-time monitoring techniques to guide regenerative therapies intra- and postoperatively. Thus, we developed an ul- trasound (US), photoacoustic (PA), and magnetic resonance (MR) imaging approach augmented with Prussian blue nanocubes (PBNCs) to guide stem cell injections intraoperatively and monitor stem cell therapies in the spinal cord postoperatively. Per the clinical procedure, a multi-level laminectomy was performed in rats ex vivo, and PBNC-labeled stem cells were injected directly into the spinal cord while US/PA images were acquired. US/ PA/MR images were also acquired post-surgery. Several features of the imaging approach were demonstrated including detection of low stem cell concentrations, real-time needle guidance and feedback on stem cell de- livery, and good agreement between US/PA/MR images. These benefits span intra- and postoperative en- vironments to support future development of this imaging tool.