In vivo magnetic resonance imaging of mesenchymal stem cells in myocardial infarction

Background - We investigated the potential of magnetic resonance imaging (MRI) to track magnetically labeled mesenchymal stem cells (MR-MSCs) in a swine myocardial infarction (MI) model. Methods and Results - Adult farm pigs (n=5) were subjected to closed-chest experimental MI. MR-MSCs (2.8 to 16×107 cells) were injected intramyocardially under x-ray fluoroscopy. MRIs were obtained on a 1.5T MR scanner to demonstrate the location of the MR-MSCs and were correlated with histology. Contrast-enhanced MRI demonstrated successful injection in the infarct and serial MSC tracking was demonstrated in two animals. Conclusion - MRI tracking of MSCs is feasible and represents a preferred method for studying the engraftment of MSCs in MI

MR-trackable intramyocardial injection catheter

There is growing interest in delivering cellular agents to infarcted myocardium to prevent postinfarction left ventricular remodeling. MRI can be effectively used to differentiate infarcted from healthy myocardium. MR-guided delivery of cellular agents/therapeutics is appealing because the therapeutics can be precisely targeted to the desired location within the infarct. In this study, a steerable intramyocardial injection catheter that can be actively tracked under MRI was developed and tested. The components of the catheter were arranged to form a loopless RF antenna receiver coil that enabled active tracking. Feasibility studies were performed in canine and porcine myocardial infarction models. Myocardial delayed-enhancement (MDE) imaging identified the infarcted myocardium, and real-time MRI was used to guide left ventricular catheterization from a carotid artery approach. The distal 35 cm of the catheter was seen under MRI with a bright signal at the distal tip of the catheter. The catheter was steered into position, the distal tip was apposed against the infarct, the needle was advanced, and a bolus of MR contrast agent and tissue marker dye was injected intramyocardially, as confirmed by imaging and post-mortem histology. A pilot study involving intramyocardial delivery of magnetically labeled stem cells demonstrated the utility of the active injection catheter system. © 2004 Wiley-Liss, Inc

Multifunctional Theranostic Graphene Oxide Nanoflakes as MR Imaging Agents with Enhanced Photothermal and Radiosensitizing Properties

The integration of multiple therapeutic and diagnostic functions into a single nanoplatform for image-guided cancer therapy has been an emerging trend in nanomedicine. We show here that multifunctional theranostic nanostructures consisting of superparamagnetic iron oxide (SPIO) and gold nanoparticles (AuNPs) scaffolded within graphene oxide nanoflakes (GO-SPIO-Au NFs) can be used for dual photo/radiotherapy by virtue of the near-infrared (NIR) absorbance of GO for photothermal therapy (PTT) and the Z element radiosensitization of AuNPs for enhanced radiation therapy (RT). At the same time, this nanoplatform can also be detected by magnetic resonance (MR) imaging because of the presence of SPIO NPs. Using a mouse carcinoma model, GO-SPIO-Au NF-mediated combined PTT/RT exhibited a 1.85-fold and 1.44-fold higher therapeutic efficacy compared to either NF-mediated PTT or RT alone, respectively, resulting in a complete eradication of tumors. As a sensitive multifunctional theranostic platform, GO-SPIO-Au NFs appear to be a promising nanomaterial for enhanced cancer imaging and therapy. © 2021 American Chemical Society

Folate receptor-targeted nanoprobes for molecular imaging of cancer: Friend or foe?

Molecular imaging (MI) of cancer is an emerging field in diagnostic imaging that provides means for visualization, characterization, and quantification of cancer biology in vivo. Various targeted nanoprobes (NPs) have been introduced to enhance signal and/or contrast, binding avidity, and targeting specificity for early detection of cancer. The overexpressed pattern of folate receptors (FRs) on the surface of cancer cells is overall distinct from normal cells. Therefore, folic acid (FA) or folate-conjugated NPs have gained much interest as diagnostic agents, therapeutics, and their combined use as theranostics for targeting FR-overexpressing tumor cells. A major advantage of FR-specific MI approaches is the high affinity of the ligand and its receptor. NPs can be designed for various clinical imaging modalities, including magnetic resonance imaging, computed tomography, optical and nuclear imaging, and ultrasonography. However, aside from the presence of high FR numbers in the normal kidney, a major challenge is the high non-specific uptake of both FA-targeted and non-targeted NPs in the liver and spleen, as evidenced by the lack of clinical trials using FA-NPs. This article summarizes the recent advancements that have been made with FR-specific MI methods and discusses the challenges for future clinical translation of FA-conjugated NPs. © 2021 Elsevier Lt