Development of an Effective Tumor-Targeted Contrast Agent for Magnetic Resonance Imaging Based on Mn/H-Ferritin Nanocomplexes

Mn-Based MRI Contrast Agents: An Overview

MRI contrast agents are required in the clinic to detect some pathologies, such as cancers. Nevertheless, at the moment, only small extracellular and non-specific gadolinium complexes are available for clinicians. Moreover, safety issues have recently emerged concerning the use of gadolinium complexes; hence, alternatives are urgently needed. Manganese-based MRI contrast agents could be one of these alternatives and increasing numbers of studies are available in the literature. This review aims at synthesizing all the research, from small Mn complexes to nanoparticular agents, including theranostic agents, to highlight all the efforts already made by the scientific community to obtain highly efficient agents but also evidence of the weaknesses of the developed systems.

An iron(III) complex-based supramolecular organic framework (SOF) as a theranostic platform via magnetic resonance imaging-guided chemotherapy

It is crucially important to explore the additional metal-endowed functions of supramolecular organic frameworks (SOFs) for expanding their applications. In this work we have reported the performance of a SOF (designated as Fe(III)-SOF) as a theranostic platform via magnetic resonance imaging (MRI)-guided chemotherapy. The Fe(III)-SOF may be used as an MRI contrast agent for cancer diagnosis because the building unit (iron complex) contains high spin iron(III) ions. Additionally, the Fe(III)-SOF may also be used as a drug carrier because it possesses stable internal voids. We loaded doxorubicin (DOX) into the Fe(III)-SOF to obtain a DOX@Fe(III)-SOF. The Fe(III)-SOF showed good loading content (16.3%) and high loading efficiency (65.2%) for DOX. Additionally, the DOX@Fe(III)-SOF had a relatively modest relaxivity value (r₂ = 19.745 mM^-1 s^-1) and exhibited the strongest negative contrast (darkest) at 12 h of post-injection. Furthermore, the DOX@Fe(III)-SOF effectively inhibited tumor growth and showed high anticancer efficiency. In addition, the Fe(III)-SOF was biocompatible and biosafe. Therefore, the Fe(III)-SOF was an excellent theranostic platform and may have potential applications in tumor diagnosis and treatment in the future. We believe that this work will initiate extensive research endeavors not only on the development of SOFs, but also on the construction of theranostic platforms based on SOFs.

Specific immunosuppressive role of nanodrugs targeting calcineurin in innate myeloid cells

Calcineurin (CN) inhibitors currently used to avoid transplant rejection block the activation of adaptive immune responses but also prevent the development of tolerance toward the graft, by directly inhibiting T cells. CN, through the transcription factors of the NFAT family, plays an important role also in the differentiation dendritic cells (DCs), the main cells responsible for the activation of T lymphocytes. Therefore, we hypothesized that the inhibition of CN only in DCs and not in T cells could be sufficient to prevent T cell responses, while allowing for the development of tolerance. Here, we show that inhibition of CN/NFAT pathway in innate myeloid cells, using a new nanoconjugate capable of selectively targeting phagocytes in vivo, protects against graft rejection and induces a longer graft acceptance compared to common CN inhibitors. We propose a new generation of nanoparticles-based selective immune suppressive agents for a better control of transplant acceptance.

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Calcineurin/NFATc2 pathway is required to enable DC migration to draining lymph nodes

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Calcineurin/NFATc2 pathway in DCs is required for type I immune responses activation

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Superparamagnetic iron oxide NPs can be used to efficiently target phagocytes in vivo

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Specific delivery of calcineurin inhibitor by NPs to phagocytes induce graft acceptance

Safe magnetic resonance imaging on biocompatible nanoformulations

Magnetic resonance imaging (MRI) holds promise for the early clinical diagnosis of various diseases, but most clinical MR techniques require the use of a contrast medium. Several nanomaterial (NM) mediated contrast agents (CAs) are widely used as T1- and T2-based MR contrast agents for clinical and non-clinical applications. Unfortunately, most NM-based CAs are toxic or non-biocompatible, restricting their practical/clinical applications. Therefore, the development of nontoxic and biocompatible CAs for clinical MRI diagnosis is highly desired. To this end, several biocompatible and biomimetic strategies have been developed to offer long blood circulation time, significant biocompatibility, in vivo biodistribution and high contrast ability for efficient imaging. However, detailed review reports on biocompatible NMs, specifically for MR imaging have not yet been summarized. Thus, in the present review we summarize  various surface coating strategies (such as polymers, proteins, cell membranes, etc.) to achieve biocompatible NPs, providing a detailed discussion of advances and future prospects for safe MRI imaging.