T₁-MRI Fluorescent Iron Oxide Nanoparticles by Microwave Assisted Synthesis

Exceedingly Small Magnetic Iron Oxide Nanoparticles for T1 -Weighted Magnetic Resonance Imaging and Imaging-Guided Therapy of Tumors

Magnetic iron oxide nanoparticles (MIONs) based T2 -weighted magnetic resonance imaging (MRI) contrast agents (CAs) are liver-specific with good biocompatibility, but have been withdrawn from the market and replaced with Eovist (Gd-EOB-DTPA) due to their inherent limitations (e.g., susceptibility to artifacts, high magnetic moment, dark signals, long processing time of T2 imaging, and long waiting time for patients after administration). Without the disadvantages of Gd-chelates and MIONs, the recently emerging exceedingly small MIONs (ES-MIONs) (<5 nm) are promising T1 CAs for MRI. However, there are rare review articles focusing on ES-MIONs for T1 -weighted MRI. Herein, the recent progress of ES-MIONs, including synthesis methods (the current basic synthesis methods and improved methods), surface modifications (artificial polymers, natural polymers, zwitterions, and functional protein), T1 -MRI visual strategies (structural remodeling, reversible self-assemblies, metal ions doped, T1 /T2 dual imaging modes, and PET/MRI strategy), and imaging-guided cancer therapy (chemotherapy, gene therapy, ferroptosis therapy, photothermal therapy, photodymatic therapy, radiotherapy, immuotherapy, sonodynamic therapy, and multimode therapy), is summarized. The detailed description of synthesis methods and applications of ES-MIONs in this review is anticipated to attract extensive interest from researchers in different fields and promote their participation in the establishment of ES-MIONs based nanoplatforms for tumor theranostics.

Synthesis and preclinical application of a Prussian blue-based dual fluorescent and magnetic contrast agent (CA)

The aim of this study was to develop and characterize a Prussian Blue based biocompatible and chemically stable T1 magnetic resonance imaging (MRI) contrast agent with near infrared (NIR) optical contrast for preclinical application. The physical properties of the Prussian blue nanoparticles (PBNPs) (iron (II); iron (III);octadecacyanide) were characterized with dynamic light scattering (DLS), zeta potential measurement, atomic force microscopy (AFM), and transmission electron microscopy (TEM). In vitro contrast enhancement properties of PBNPs were determined by MRI. In vivo T1-weighted contrast of the prepared PBNPs was investigated by MRI and optical imaging modality after intravenous administration into NMRI-Foxn1 nu/nu mice. The biodistribution studies showed the presence of PBNPs predominantly in the cardiovascular system. Briefly, in this paper we show a novel approach for the synthesis of PBNPs with enhanced iron content for T1 MRI contrast. This newly synthetized PBNP platform could lead to a new diagnostic agent, replacing the currently used Gadolinium based substances.

Biomineralized iron oxide-polydopamine hybrid nanodots for contrast-enhanced T1-weighted magnetic resonance imaging and photothermal tumor ablation

Iron oxide nanoparticles (IO NPs) have become the focus of molecular imaging probes for contrast enhanced magnetic resonance (MR) imaging due to their intrinsic magnetic and biodegradable properties, as well as long blood half-lives and low toxicity. Massive efforts have been made to explore the IO NPs as T2-weighted MR contrast agents, which have high susceptibility to induce a long-range magnetic field that interferes with diagnosis. Thus, the development of IO NPs with potent T1 relaxivity might help in providing an alternative for clinically applied gadolinium chelates. Herein, biomineralized iron oxide-polydopamine hybrid nanodots (IO/PDA-NDs) have been constructed using albumin as the nanoreactors to induce nanoprecipitation and polymerization simultaneously, facilitating T1-weighted contrast-enhancement as well as photothermal therapeutic capability. The IO nanoclusters in IO/PDA-NDs have an r1 relaxivity of 5.79 mM-1 s-1 with a relatively low r2/r1 ratio of 1.71, demonstrating the preferable iron oxide based T1 contrast agents. The high photothermal conversion coefficient and tumor targeting effect of the hybrid nanodots could result in complete tumor ablation efficacy. The biomineralization method provides a promising approach for the integration of tumor diagnosis and treatment to achieve efficient cancer theranostics.

Heparin length in the coating of extremely small iron oxide nanoparticles regulates in vivo theranostic applications

The positive contrast of extremely small iron oxide nanoparticles (ESIONP) in magnetic resonance imaging (MRI) rejuvenates this class of metal nanoparticles (NP).Yet, the current synthesis often lacks the possibility of adjusting the core size (while it is a key element for ESIONP-based MRI contrast behaviour), and also involved multiple complex steps before obtaining a ready-to-use probe for medical applications. In this study, we faced these challenges by applying heparin oligosaccharides (HO) of different lengths as coatings for the preparation of HEP-ESIONP with a one-pot microwave method. We demonstrated that the HO length could control the core size during the synthesis to achieve optimal positive MRI contrast, and that HEP-ESIONP were endowed directly with anticoagulant properties and/or a specific antitumor activity, according to the HO used. Relevantly, positron emission tomography (PET)-based in vivo biodistribution study conducted with 68Ga core-doped HEP-ESIONP analogues revealed significant changes in the probe behaviours, the shortening of HO promoting a shift from hepatic to renal clearance. The different conformations of HO coatings and a thorough in vitro characterisation of the probes' protein coronas provided insight into this crucial impact of HO length on opsonization-mediated immune response and elimination. Overall, we were able to identify a precise HO length to get an ESIONP probe showing prolonged vascular lifetime and moderate accumulation in a tumor xenograft, balanced with a low uptake by non-specific organs and favourable urinary clearance. This probe met all prerequisites for advanced theranostic medical applications with a dual MRI/PET hot spot capability and potential antitumor activity.

Magnetofluorescent Nanoprobe for Multimodal and Multicolor Bioimaging

Although, superparamagnetic iron oxide nanoparticles (SPIONs) have extensively been used as a contrasting agent for magnetic resonance imaging (MRI), the lack of intrinsic fluorescence restricted their application as a multimodal probe, especially in combination with light microscopy. In Addition, the bigger size of the particle renders them incompetent for bioimaging of small organelles. Herein, we report, not only the synthesis of ultrasmall carbon containing magneto-fluorescent SPIONs with size ∼5 nm, but also demonstrate its capability as a multicolor imaging probe. Using MCF-7 and HeLa cell lines, we show that the SPIONs can provide high contrast mulicolor images of the cytoplasm from blue to red region. Further, single particle level photon count data revealed that the SPIONs could efficaciously be utilized in localization based super resolution microscopy in future.

Iron Oxide Nanoparticles: An Alternative for Positive Contrast in Magnetic Resonance Imaging

Iron oxide nanoparticles have been extensively utilised as negative (T2) contrast agents in magnetic resonance imaging. In the past few years, researchers have also exploited their application as positive (T1) contrast agents to overcome the limitation of traditional Gd3+ contrast agents. To provide T1 contrast, these particles must present certain physicochemical properties with control over the size, morphology and surface of the particles. In this review, we summarise the reported T1 iron oxide nanoparticles and critically revise their properties, synthetic protocols and application, not only in MRI but also in multimodal imaging. In addition, we briefly summarise the most important nanoparticulate Gd and Mn agents to evaluate whether T1 iron oxide nanoparticles can reach Gd/Mn contrast capabilities.

The Transition from Metal-Based to Metal-Free Contrast Agents for T1 Magnetic Resonance Imaging Enhancement

Magnetic resonance imaging (MRI) has received significant attention as the noninvasive diagnostic technique for complex diseases. Image-guided therapeutic strategy for diseases such as cancer has also been at the front line of biomedical research, thanks to the innovative MRI, enhanced by the prior delivery of contrast agents (CAs) into patients' bodies through injection. These CAs have contributed a great deal to the clinical utility of MRI but have been based on metal-containing compounds such as gadolinium, manganese, and iron oxide. Some of these CAs have led to cytotoxicities such as the incurable Nephrogenic Systemic Fibrosis (NSF), resulting in their removal from the market. On the other hand, CAs based on organic nitroxide radicals, by virtue of their structural composition, are metal free and without the aforementioned drawbacks. They also have improved biocompatibility, ease of functionalization, and long blood circulation times, and have been proven to offer tissue contrast enhancement with longitudinal relaxivities comparable with those for the metal-containing CAs. Thus, this Review highlights the recent progress in metal-based CAs and their shortcomings. In addition, the remarkable goals achieved by the organic nitroxide radical CAs in the enhancement of MR images have also been discussed extensively. The focal point of this Review is to emphasize or demonstrate the crucial need for transition into the use of organic nitroxide radicals-metal-free CAs-as against the metal-containing CAs, with the aim of achieving safer application of MRI for early disease diagnosis and image-guided therapy.

Microwave-Driven Synthesis of Iron-Oxide Nanoparticles for Molecular Imaging

Here, we present a comprehensive review on the use of microwave chemistry for the synthesis of iron-oxide nanoparticles focused on molecular imaging. We provide a brief introduction on molecular imaging, the applications of iron oxide in biomedicine, and traditional methods for the synthesis of these nanoparticles. The review then focuses on the different examples published where the use of microwaves is key for the production of nanoparticles. We study how the different parameters modulate nanoparticle properties, particularly for imaging applications. Finally, we explore principal applications in imaging of microwave-produced iron-oxide nanoparticles.

Label Free Ultrasmall Fluoromagnetic Ferrite-clusters for Targeted Cancer Imaging and Drug Delivery

OBJECTIVE

The label free ultrasmall fluorescent ferrite clusters have been engineered in a controlled fashion which was stabilized by serum protein and functionalized by folic acid for the application of targeted multimodal optical and Magnetic Resonance (MR) cancer imaging.

METHODS

The ultra-small manganese ferrite nanoclusters (PMNCs) with a diameter of 4 nm have a commendable effect on the longitudinal (T1) and transverse (T2) relaxation in MR imaging that was evident from the phantom and animal MRI.

RESULTS

The calculated longitudinal molar relaxivity of nanoclusters was found to be 6.9 ± 0.10 mM-1 S-1 which was exactly 2.22 times better than the conventional Gd-DOTA and their 4.01 ratio of the transverse (r2) and longitudinal (r1) relaxivities made them a potential candidate for both T1 and T2 contrast agents in MRI. In addition, the fluorescence-based small animal imaging showed folic acid driven accumulated fluorescent signal at the tumour site to conclude the capacity of PMNCs for targeted fluorescence imaging of cancer diagnosis.

CONCLUSION

The cytotoxicity assay and histopathology studies were the evidence for their safe biodistribution in animal systems. Furthermore, the protein encapsulated clusters have the ability to deliver the anticancer drug Methotrexate (MTX) to the cancer tissues with a sustained manner. Therefore, one can conclude the remarkable efficacy of architect nanoclusters for theragnosis.

Wet chemical synthesis of metal oxide nanoparticles: a review

Metal oxide nanoparticles are an important class of nanomaterials that have found several applications in science and technology.

Synthesis, Functionalization, and Design of Magnetic Nanoparticles for Theranostic Applications

In order to translate nanotechnology into medical practice, magnetic nanoparticles (MNPs) have been presented as a class of non-invasive nanomaterials for numerous biomedical applications. In particular, MNPs have opened a door for simultaneous diagnosis and brisk treatment of diseases in the form of theranostic agents. This review highlights the recent advances in preparation and utilization of MNPs from the synthesis and functionalization steps to the final design consideration in evading the body immune system for therapeutic and diagnostic applications with addressing the most recent examples of the literature in each section. This study provides a conceptual framework of a wide range of synthetic routes classified mainly as wet chemistry, state-of-the-art microfluidic reactors, and biogenic routes, along with the most popular coating materials to stabilize resultant MNPs. Additionally, key aspects of prolonging the half-life of MNPs via overcoming the sequential biological barriers are covered through unraveling the biophysical interactions at the bio-nano interface and giving a set of criteria to efficiently modulate MNPs' physicochemical properties. Furthermore, concepts of passive and active targeting for successful cell internalization, by respectively exploiting the unique properties of cancers and novel targeting ligands are described in detail. Finally, this study extensively covers the recent developments in magnetic drug targeting and hyperthermia as therapeutic applications of MNPs. In addition, multi-modal imaging via fusion of magnetic resonance imaging, and also innovative magnetic particle imaging with other imaging techniques for early diagnosis of diseases are extensively provided.

In vivo imaging of lung inflammation with neutrophil-specific 68Ga nano-radiotracer

In vivo detection and quantification of inflammation is a major goal in molecular imaging. Furthermore, cell-specific detection of inflammation would be a tremendous advantage in the characterization of many diseases. Here, we show how this goal can be achieved through the synergistic combination of nanotechnology and nuclear imaging. One of the most remarkable features of this hybrid approach is the possibility to tailor the pharmacokinetics of the nanomaterial-incorporated biomolecule and radionuclide. A good example of this approach is the covalent binding of a large amount of a neutrophil-specific, hydrophobic peptide on the surface of ⁶⁸Ga core-doped nanoparticles. This new nano-radiotracer has been used for non-invasive in vivo detection of acute inflammation with very high in vivo labelling efficiency, i.e. a large percentage of labelled neutrophils. Furthermore, we demonstrate that the tracer is neutrophil-specific and yields images of neutrophil recruitment of unprecedented quality. Finally, the nano-radiotracer was successfully detected in chronic inflammation in atherosclerosis-prone ApoE^−/− mice after several weeks on a high-fat diet.

Family of Bioactive Heparin-Coated Iron Oxide Nanoparticles with Positive Contrast in Magnetic Resonance Imaging for Specific Biomedical Applications

Unfractionated heparin (UFH) and low-molecular-weight heparins (LMWH) are well-known for their anticoagulant properties. There is also currently a growing interest in using LMWH in targeted cancer therapy. In particular, several types inhibit heparanase, a key enzyme overexpressed in the tumor microenvironment that promotes angiogenesis progression and metastasis spreading. Here, we propose iron oxide nanoparticles (HEP-IONP) coated with different heparins of distinct anticoagulant/anti-heparanase activity ratios and suitable for positive contrast in magnetic resonance imaging. As a proof of concept, magnetic resonance angiography (MRA) was conducted in mice up to 3 h after intravenous administration. This new IONP-based positive contrast appropriate for clinic together with the long vascular circulating times can enable innovative theranostic applications if combined with the various bioactivities of the heparins. Indeed, we showed, using advanced in vitro tests, how HEP-IONP anticoagulant or anti-heparanase activities were maintained depending on the heparin species used for the coating. Overall, the study allowed presenting an IONP coated with a commercial LMWH (Lovenox) suggested as a theranostic translational probe for MRA diagnostic and treatment of thrombosis, and an antitumor IONP coated with a specific depolymerized heparin to be used in targeted therapy and diagnostic modalities.

Recent advances in the preparation and application of multifunctional iron oxide and liposome-based nanosystems for multimodal diagnosis and therapy

Nowadays, thanks to the successful discoveries in the biomedical field achieved in the last two decades, a deeper understanding about the complexity of mechanistic aspects of different pathological processes has been obtained. As a consequence, even the standard therapeutic protocols have undergone a vast redesign. In fact, the awareness about the necessity to progress towards a combined multitherapy in order to potentially increase the final healing chances has become a reality. One of the crucial elements of this novel approach is that large amounts of detailed information are highly needed and in vivo imaging techniques represent one of the most powerful tools to visualize and monitor the pathological state of the patient. To this scope, due to their unique features, nanostructured materials have emerged as attractive elements for the development of multifunctional tools for diagnosis and therapy. Hence, in this review, the most recent and relevant advances achieved by applying multifunctional nanostructures in multimodal theranosis of different diseases will be discussed. In more detail, the preparation and application of single multifunctional nano-radiotracers based on iron oxides and enabling PET/MRI dual imaging will be firstly detailed. After that, especially considering their highly promising clinical potential, the preparation and application of multifunctional liposomes useful for multimodal imaging and therapy will be reviewed. In both cases, a special focus will be set on the application of such a multifunctional nanocarriers in cancer as well as cardiovascular diseases.