Abstract Prior research has highlighted the reduction of iron oxide nanoparticle (IONPs) sizes to the “ultra‐small” dimension as a pivotal approach in developing T 1 ‐MRI contrast agents, and the enhancement in T 1 contrast performance with the reducing size is usually attributed to the increased specific surface area and weakened magnetization. Nonetheless, as the size decreases, the variation in surface defects, particularly oxygen vacancy (V O ) defects, significantly impacts the T 1 imaging efficacy. In this study, the V O on IONPs is meticulously investigated through XPS, Raman, and EPR spectroscopy. As the nanoparticle size decreased, the V O concentration rose initially but subsequently declined, with the peak concentration observed in the size of 8.27 nm. Further insights gained from synchrotron XAS analysis and DFT calculations indicate that both surface tension and phase transition in IONPs contribute to alterations in the Fe─O bond length, thereby influencing the V O formation energy across varying nanoparticle sizes. The MRI tests reveal that the V O in IONPs serve as pivotal sites for the attachment of water molecules to iron ions, and IONPs with fewer V O exhibited a deterioration in T 1 ‐MRI contrast effects. This research may provide a deeper understanding of the relationship between T 1 contrast performance and the size of IONPs.
ABSTRACT Contrast-enhanced magnetic resonance imaging (CE-MRI) is a pivotal tool for global disease diagnosis and management. Since its clinical availability in 2009, the off-label use of ferumoxytol for ferumoxytol-enhanced MRI (FE-MRI) has significantly reshaped CE-MRI practices. Unlike MRI that is enhanced by gadolinium-based contrast agents, FE-MRI offers advantages such as reduced contrast agent dosage, extended imaging windows, no nephrotoxicity, higher MRI time efficiency and the capability for molecular imaging. As a leading superparamagnetic iron oxide contrast agent, ferumoxytol is heralded as the next generation of contrast agents. This review delineates the pivotal clinical applications and inherent technical superiority of FE-MRI, providing an avant-garde medical-engineering interdisciplinary lens, thus bridging the gap between clinical demands and engineering innovations. Concurrently, we spotlight the emerging imaging themes and new technical breakthroughs. Lastly, we share our own insights on the potential trajectory of FE-MRI, shedding light on its future within the medical imaging realm.
Labeling of mesenchymal stem cells (MSCs) with superparamagnetic iron oxide nanoparticles (SPIONs) has emerged as a potential method for magnetic resonance imaging (MRI) tracking of transplanted cells in tissue repair studies and clinical trials. Labeling of MSCs using clinically approved SPIONs (ferumoxytol) requires the use of transfection reagents or magnetic field, which largely limits their clinical application. To overcome this obstacle, we established a novel and highly effective method for magnetic labeling of MSC spheroids using ferumoxytol. Unlike conventional methods, ferumoxytol labeling was done in the formation of a mechanically tunable biomimetic hydrogel-induced MSC spheroids. Moreover, the labeled MSC spheroids exhibited strong MRI T2 signals and good biosafety. Strikingly, the encapsulated ferumoxytol was localized in the extracellular matrix (ECM) of the spheroids instead of the cytoplasm, minimizing the cytotoxicity of ferumoxytol and maintaining the viability and stemness properties of biomimetic hydrogel-induced MSC spheroids. This demonstrates the potential of this method for post-transplantation MRI tracking in the clinic.
Vaccine Delivery In article 2301232, Jingyi Sheng, Fang Yang, Ning Gu, and co-workers introduce a magnetic-responsive cancer vaccine, employing antigen-loaded magnetic liposomes (Ag-MLs), for active lymph node targeting. These liposomes, containing mouse melanoma lysate, iron oxide nanoparticles, and CpG adjuvant, display enhanced accumulation in lymph nodes when magnetically guided and demonstrate significant enhancement in anti-tumor immunity in a mouse model. This approach provides potential new avenues for developing effective tumor vaccines.
Therapeutic cancer vaccines offer the greatest advantage of enhancing antigen-specific immunity against tumors, particularly for immunogenic tumors, such as melanoma. However, clinical responses remain unsatisfactory, primarily due to inadequate T cell priming and the development of acquired immune tolerance. A major obstacle lies in the inefficient uptake of antigen by peripheral dendritic cells (DCs) and their migration to lymph nodes for antigen presentation. In this context, the magnetic delivery of antigen-loaded magnetic liposomes (Ag-MLs) to actively target lymph node, is proposed. These magnetic responsive liposomes contain soluble mouse melanoma lysate and iron oxide nanoparticles in the core, along with the immunostimulatory adjuvant CpG-1826 incorporated into the lipid bilayer. When applied through magnetic targeting in the mouse melanoma model, Ag-MLs accumulate significantly in the target lymph nodes. This accumulation results in increased population of active DCs in lymph nodes and cytotoxic T lymphocytes (CTLs) within tumors, correlating with effective tumor growth inhibition. Overall, this study demonstrates the potential of magnetic targeting as an effective strategy for delivering cancer vaccines and activating the immune response, offering a novel platform for cancer immunotherapies.
Atherosclerosis (AS) is a serious disease that poses a significant threat to the global population. In this review, we analyze the development of AS from multiple perspectives, aiming to elucidate its molecular mechanisms. We also focus on imaging techniques and therapeutic approaches, highlighting the crucial role of nanomaterials in both imaging and therapy for AS. By leveraging their compatibility and targeting capabilities, nanomaterials can be integrated with traditional medical imaging and therapeutic agents to achieve targeted drug delivery, controlled release, and precise localization and imaging of atherosclerotic plaques.
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