OxLDL-targeted iron oxide nanoparticles for in vivo MRI detection of perivascular carotid collar induced atherosclerotic lesions in ApoE-deficient mice

Iron Oxide Nanoparticles in Regenerative Medicine and Tissue Engineering

In recent years, many promising nanotechnological approaches to biomedical research have been developed in order to increase implementation of regenerative medicine and tissue engineering in clinical practice. In the meantime, the use of nanomaterials for the regeneration of diseased or injured tissues is considered advantageous in most areas of medicine. In particular, for the treatment of cardiovascular, osteochondral and neurological defects, but also for the recovery of functions of other organs such as kidney, liver, pancreas, bladder, urethra and for wound healing, nanomaterials are increasingly being developed that serve as scaffolds, mimic the extracellular matrix and promote adhesion or differentiation of cells. This review focuses on the latest developments in regenerative medicine, in which iron oxide nanoparticles (IONPs) play a crucial role for tissue engineering and cell therapy. IONPs are not only enabling the use of non-invasive observation methods to monitor the therapy, but can also accelerate and enhance regeneration, either thanks to their inherent magnetic properties or by functionalization with bioactive or therapeutic compounds, such as drugs, enzymes and growth factors. In addition, the presence of magnetic fields can direct IONP-labeled cells specifically to the site of action or induce cell differentiation into a specific cell type through mechanotransduction.

Evaluation of Plaque Characteristics and Inflammation Using Magnetic Resonance Imaging

Atherosclerosis is an inflammatory disease of large and medium-sized arteries, characterized by the growth of atherosclerotic lesions (plaques). These plaques often develop at inner curvatures of arteries, branchpoints, and bifurcations, where the endothelial wall shear stress is low and oscillatory. In conjunction with other processes such as lipid deposition, biomechanical factors lead to local vascular inflammation and plaque growth. There is also evidence that low and oscillatory shear stress contribute to arterial remodeling, entailing a loss in arterial elasticity and, therefore, an increased pulse-wave velocity. Although altered shear stress profiles, elasticity and inflammation are closely intertwined and critical for plaque growth, preclinical and clinical investigations for atherosclerosis mostly focus on the investigation of one of these parameters only due to the experimental limitations. However, cardiovascular magnetic resonance imaging (MRI) has been demonstrated to be a potent tool which can be used to provide insights into a large range of biological parameters in one experimental session. It enables the evaluation of the dynamic process of atherosclerotic lesion formation without the need for harmful radiation. Flow-sensitive MRI provides the assessment of hemodynamic parameters such as wall shear stress and pulse wave velocity which may replace invasive and radiation-based techniques for imaging of the vascular function and the characterization of early plaque development. In combination with inflammation imaging, the analyses and correlations of these parameters could not only significantly advance basic preclinical investigations of atherosclerotic lesion formation and progression, but also the diagnostic clinical evaluation for early identification of high-risk plaques, which are prone to rupture. In this review, we summarize the key applications of magnetic resonance imaging for the evaluation of plaque characteristics through flow sensitive and morphological measurements. The simultaneous measurements of functional and structural parameters will further preclinical research on atherosclerosis and has the potential to fundamentally improve the detection of inflammation and vulnerable plaques in patients.

Tailoring Iron Oxide Nanoparticles for Efficient Cellular Internalization and Endosomal Escape

Iron oxide nanoparticles (IONs) have been widely explored for biomedical applications due to their high biocompatibility, surface-coating versatility, and superparamagnetic properties. Upon exposure to an external magnetic field, IONs can be precisely directed to a region of interest and serve as exceptional delivery vehicles and cellular markers. However, the design of nanocarriers that achieve an efficient endocytic uptake, escape lysosomal degradation, and perform precise intracellular functions is still a challenge for their application in translational medicine. This review highlights several aspects that mediate the activation of the endosomal pathways, as well as the different properties that govern endosomal escape and nuclear transfection of magnetic IONs. In particular, we review a variety of ION surface modification alternatives that have emerged for facilitating their endocytic uptake and their timely escape from endosomes, with special emphasis on how these can be manipulated for the rational design of cell-penetrating vehicles. Moreover, additional modifications for enhancing nuclear transfection are also included in the design of therapeutic vehicles that must overcome this barrier. Understanding these mechanisms opens new perspectives in the strategic development of vehicles for cell tracking, cell imaging and the targeted intracellular delivery of drugs and gene therapy sequences and vectors.

Recent advances in molecular imaging of atherosclerotic plaques and thrombosis

As the complications of atherosclerosis such as myocardial infarction and stroke are still one of the leading causes of mortality worldwide, the development of new diagnostic tools for the early detection of plaque instability and thrombosis is urgently needed. Advanced molecular imaging probes based on functional nanomaterials in combination with cutting edge imaging techniques are now paving the way for novel and unique approaches to monitor the inflammatory progress in atherosclerosis. This review focuses on the development of various molecular probes for the diagnosis of plaques and thrombosis in atherosclerosis, along with perspectives of their diagnostic applications in cardiovascular diseases. Specifically, we summarize the biological targets that can be used for atherosclerosis and thrombosis imaging. Then we describe the emerging molecular imaging techniques based on the utilization of engineered nanoprobes together with their challenges in clinical translation.

Small Dimension-Big Impact! Nanoparticle-Enhanced Non-Invasive and Intravascular Molecular Imaging of Atherosclerosis In Vivo

Extensive translational research has provided considerable progress regarding the understanding of atherosclerosis pathophysiology over the last decades. In contrast, implementation of molecular in vivo imaging remains highly limited. In that context, nanoparticles represent a useful tool. Their variable shape and composition assure biocompatibility and stability within the environment of intended use, while the possibility of conjugating different ligands as well as contrast dyes enable targeting of moieties of interest on a molecular level and visualization throughout various imaging modalities. These characteristics have been exploited by a number of preclinical research approaches aimed at advancing understanding of vascular atherosclerotic disease, in order to improve identification of high-risk lesions prior to oftentimes fatal thromboembolic events. Furthermore, the combination of these targeted nanoparticles with therapeutic agents offers the potential of site-targeted drug delivery with minimized systemic secondary effects. This review gives an overview of different groups of targeted nanoparticles, designed for in vivo molecular imaging of atherosclerosis as well as an outlook on potential combined diagnostic and therapeutic applications.

Recent Advances in Managing Atherosclerosis via Nanomedicine

Atherosclerosis, driven by chronic inflammation of the arteries and lipid accumulation on the blood vessel wall, underpins many cardiovascular diseases with high mortality rates globally, such as stroke and ischemic heart disease. Engineered bio-nanomaterials are now under active investigation as carriers of therapeutic and/or imaging agents to atherosclerotic plaques. This Review summarizes the latest bio-nanomaterial-based strategies for managing atherosclerosis published over the past five years, a period marked by a rapid surge in preclinical applications of bio-nanomaterials for imaging and/or treating atherosclerosis. To start, the biomarkers exploited by emerging bio-nanomaterials for targeting various components of atherosclerotic plaques are outlined. In addition, recent efforts to rationally design and screen for bio-nanomaterials with the optimal physicochemical properties for targeting plaques are presented. Moreover, the latest preclinical applications of bio-nanomaterials as carriers of imaging, therapeutic, or theranostic agents to atherosclerotic plaques are discussed. Finally, a mechanistic understanding of the interactions between bio-nanomaterials and the plaque ("athero-nano" interactions) is suggested, the opportunities and challenges in the clinical translation of bio-nanomaterials for managing atherosclerosis are discussed, and recent clinical trials for atherosclerotic nanomedicines are introduced.

Anti-connective tissue growth factor detects and reduces plaque inflammation in early-stage carotid atherosclerotic lesions

This study explored connective tissue growth factor (CTGF)-targeted ultrasmall superparamagnetic iron oxides (USPIOs) for noninvasive MRI of CTGF within carotid atherosclerotic lesions in apoE-deficient (apoE^-/-) mice. Anti-CTGF polyclonal and nonspecific IgG antibodies were conjugated to polyethylene glycol-coated USPIOs, and apoE^-/- carotid partial ligation-model mice were imaged via MRI before and after contrast administration. ApoE^-/- mice were treated with CTGF-neutralizing antibodies for 3 weeks. Carotid artery diameter and plaque volume were measured via MRI in IgG and CTGF antibody-treated groups. Anti-CTGF-USPIO-treated macrophages showed the greatest iron uptake. MRI signal loss was observed in carotid atherosclerotic lesions 24 h after anti-CTGF-USPIO administration, consistent with the presence of nanoparticles, as indicated by pathological examinations. Atheromata in anti-CTGF-treated mice showed reduced macrophage deposition, CTGF expression, and plaque volume. Anti-CTGF-USPIOs can be used for the direct detection of CTGF and imaging of atherosclerotic lesions in vivo. CTGF is a potential therapeutic target for treating atherosclerosis.

Assessment of renal function in the anaesthetised rat following injection of superparamagnetic iron oxide nanoparticles

A recent study showed that a significant fall in mean arterial pressure (MAP) occurred following intravenous injection of two novel superparamagnetic iron oxide nanoparticles (SPIONs), MF66 and OD15. To assess if this was caused by excessive glomerular clearance, the effect of both particles on renal function was studied. Experiments were performed on sodium pentobarbital anaesthetised male Wistar rats (250–350 g). Twenty-minute urine clearances were taken followed by an i.v. bolus of MF66, OD15 (2 mg·kg–1), or dH2O (0.4 mL·kg–1). MF6 or OD15 injection resulted in a significant transient drop in MAP and renal blood flow by approximately 33% and 50% (P < 0.05). The absolute excretion of sodium was significantly increased (P < 0.05) by almost 80% and 70% following OD15 and MF66, respectively. Similarly, fractional excretion of sodium was increased by almost 80% and 60% following OD15 and MF66, respectively. The glomerular filtration rate was not significantly affected, but urine flow increased nonsignificantly by approximately 50% and 66% following i.v. injection of OD15 and MF66, respectively. SPIONs produce a decrease in blood pressure and a natriuresis; however, the rate of fluid filtration in the kidney was not significantly affected.

MRI detection of endothelial cell inflammation using targeted superparamagnetic particles of iron oxide (SPIO)

Background

There is currently no clinical imaging technique available to assess the degree of inflammation associated with atherosclerotic plaques. This study aims to develop targeted superparamagnetic particles of iron oxide (SPIO) as a magnetic resonance imaging (MRI) probe for detecting inflamed endothelial cells.

Methods

The in vitro study consists of the characterisation and detection of inflammatory markers on activated endothelial cells by immunocytochemistry and MRI using biotinylated anti-P-selectin and anti-VCAM-1 (vascular cell adhesion molecule 1) antibody and streptavidin conjugated SPIO.

Results

Established an in vitro cellular model of endothelial inflammation induced with TNF-α (tumor necrosis factor alpha). Inflammation of endothelial cells was confirmed with both immunocytochemistry and MRI. These results revealed both a temporal and dose dependent expression of the inflammatory markers, P-selectin and VCAM-1, on exposure to TNF-α.

Conclusion

This study has demonstrated the development of an in vitro model to characterise and detect inflamed endothelial cells by immunocytochemistry and MRI. This will allow the future development of contrast agents and protocols for imaging vascular inflammation in atherosclerosis. This work may form the basis for a translational study to provide clinicians with a novel tool for the in vivo assessment of atherosclerosis.

Imaging of carotid artery inflammatory plaques with superparamagnetic nanoparticles and an external magnet collar

Stroke is one of the top three fatal diseases in human history.

LOX-1-Targeted Iron Oxide Nanoparticles Detect Early Diabetic Nephropathy in db/db Mice

PURPOSE

Activation of the low-density lipoprotein receptor 1 (LOX-1) contributes to pervasive inflammation in early diabetic nephropathy (DN). This study determined the feasibility of anti-LOX-1-ultrasmall superparamagnetic iron oxide nanoparticles (USPIOs) for noninvasive detection of inflammatory renal lesions in early DN.

PROCEDURES

Anti-mouse LOX-1 antibody was conjugated to polyethyleneglycol-coated USPIOs. In vitro analysis of USPIOs uptake was performed in RAW264.7 macrophages. DN and control mice were imaged by MRI prior to and 24 h after contrast treatment.

RESULTS

Anti-LOX-1 USPIOs were selectively taken up by macrophages, and kidney T2* MRI showed a lower signal intensity in the cortex of DN mice after 24 h administration of anti-LOX-1 USPIOs. Positive Perl's staining in DN lesions, indicating the presence of iron oxide, was consistent with immunohistochemistry indicating the presence of LOX-1 and CD68.

CONCLUSIONS

This report shows that anti-LOX-1 USPIOs detect LOX-1-enriched inflammatory renal lesions in early DN mice. Our study provides important information for characterizing and monitoring early DN.

Small is Smarter: Nano MRI Contrast Agents - Advantages and Recent Achievements

Many challenges for advanced sensitive and noninvasive clinical diagnostic imaging remain unmatched. In particular, the great potential of magnetic nano-probes is intensively discussed to further improve the performance of magnetic resonance imaging (MRI), especially for cancer diagnosis. Based on recent achievements, here the concepts of magnetic nanoparticle-based MRI contrast agents and tumor-specific imaging probes are critically summarized. Advances in their synthesis, biocompatible chemical and biofunctional surface modifications, and current strategies for further developing them into multimodality imaging probes are discussed. In addition, how engineered versus unintended surface coatings such as protein coronas affect the biocompatibility and performance of MRI nano-probes is also considered. To stimulate progress in the field, future strategies and relevant challenges that still need to be resolved in the field conclude this review.

Advances in MRI for the evaluation of carotid atherosclerosis

Carotid artery atherosclerosis is an important source of mortality and morbidity in the Western world with significant socioeconomic implications. The quest for the early identification of the vulnerable carotid plaque is already in its third decade and traditional measures, such as the sonographic degree of stenosis, are not selective enough to distinguish those who would really benefit from a carotid endarterectomy. MRI of the carotid plaque enables the visualization of plaque composition and specific plaque components that have been linked to a higher risk of subsequent embolic events. Blood suppressed T1 and T2 weighted and proton density-weighted fast spin echo, gradient echo and time-of-flight sequences are typically used to quantify plaque components such as lipid-rich necrotic core, intraplaque haemorrhage, calcification and surface defects including erosion, disruption and ulceration. The purpose of this article is to review the most important recent advances in MRI technology to enable better diagnostic carotid imaging.

C5b-9-targeted molecular MR imaging in rats with Heymann nephritis: a new approach in the evaluation of nephrotic syndrome

Membranous nephropathy (MN) is the major cause of adult nephrotic syndrome, which severely affects patients’ quality of life. Currently, percutaneous renal biopsy is required to definitively diagnose MN. However, this technique is invasive and may cause severe complications. Therefore, an urgent clinical need exists for dynamic noninvasive monitoring of the renal state. In-depth molecular imaging studies could assist in finding a solution. Membrane attack complex C5b-9 is the key factor in the development of MN, and this protein primarily deposits in the glomerulus. The present study bound polyclonal antibodies to C5b-9 with ultrasmall superparamagnetic iron oxide (USPIO) nanoparticles to obtain C5b-9-targeted magnetic resonance molecular imaging probes. The probes were injected intravenously into rats with Heymann nephritis, a classic disease model of MN. The signal intensity in the T2*-weighted imaging of kidneys in vivo using 7.0 Tesla magnetic resonance imaging decreased significantly 24 hours after injection compared to the untargeted and control groups. This signal change was consistent with the finding of nanoparticle deposits in pathological glomeruli. This study demonstrated a novel molecular imaging technique for the assessment of MN.

The effect of two novel amino acid-coated magnetic nanoparticles on survival in vascular endothelial cells, bone marrow stromal cells, and macrophages

Magnetic nanoparticles (MNPs) have been popularly used in many fields. Recently, many kinds of MNPs are modified as new absorbents, which have attracted considerable attention and are promising to be applied in waste water. In our previous study, we synthesized two novel MNPs surface-coated with glycine or lysine, which could efficiently remove many anionic and cationic dyes under severe conditions. It should be considered that MNP residues in water may exert some side effects on human health. In the present study, we evaluated the potential nanotoxicity of MNPs in human endothelial cells, macrophages, and rat bone marrow stromal cells. The results showed that the two kinds of nanoparticles were consistently absorbed into the cell cytoplasm. The concentration of MNPs@Gly that could distinctly decrease survival was 15 μg/ml in human umbilical vascular endothelial cells (HUVECs) or bone marrow stromal cells (BMSCs) and 10 μg/ml in macrophages. While the concentration of MNPs@Lys that obviously reduced viability was 15 μg/ml in HUVECs or macrophages and 50 μg/ml in BMSCs. Furthermore, cell nucleus staining and cell integrity assay indicated that the nanoparticles induced cell apoptosis, but not necrosis even at a high concentration. Altogether, these data suggest that the amino acid-coated magnetic nanoparticles exert relatively high cytotoxicity. By contrast, lysine-coated magnetic nanoparticles are more secure than glycine-coated magnetic nanoparticles.

Near-infrared fluorescence imaging of murine atherosclerosis using an oxidized low density lipoprotein-targeted fluorochrome

The aim of this study was to explore the feasibility of detecting plaques using an NIR797 fluorochrome-labeled, anti-oxLDL antibody (anti-oxLDL-NIR797) and near-infrared fluorescence (NIRF) imaging in a murine model of atherosclerosis. Anti-mouse oxLDL polyclonal antibodies were conjugated to NIR797 dyes to synthesis oxLDL-targeted NIRF probe. In situ and ex vivo NIRF imaging of the high-cholesterol diet-induced atherosclerotic lesions of apoE-/- mice (baseline) as well as ex vivo NIRF imaging in the progression and regression group (without or with atorvastatin treatment for another 8 weeks) were performed 24 h after an intravenous injection of 1 mg/kg of anti-oxLDL-NIR797, while phosphate-buffered saline (PBS) was used for the controls. The plaque areas were investigated using Oil Red O (ORO) staining. Aortas isolated from the apoE-/- mice 24 h post-injection exhibited a selective, strong, heterogeneous NIRF signal enhancement in the aortic root, arch, and bifurcation, whereas the PBS and competitive inhibition groups had limited NIRF signal changes (p < 0.05). There was a significant correlation between ORO staining and NIRF in the atherosclerotic aortas that received anti-oxLDL-NIR797. Immunofluorescence studies confirmed the colocalization of the oxLDL/macrophages and NIR797 fluorochromes. Furthermore, the atherosclerotic lesions of atorvastatin-treated mice showed reduced anti-oxLDL-NIR797 uptake and oxLDL expression. These results indicate that NIRF plaque imaging is feasible with an oxLDL-targeted NIRF probe. Thus, oxLDL-based molecular imaging of atherosclerotic plaques is feasible and may provide important methods for characterizing vulnerable plaques and monitoring the response to therapeutic interventions for atherosclerosis.

Bcl-2-functionalized ultrasmall superparamagnetic iron oxide nanoparticles coated with amphiphilic polymer enhance the labeling efficiency of islets for detection by magnetic resonance imaging

Based on their versatile, biocompatible properties, superparamagnetic iron oxide (SPIO) or ultrasmall superparamagnetic iron oxide (USPIO) nanoparticles are utilized for detecting and tracing cells or tumors in vivo. Here, we developed an innoxious and concise synthesis approach for a novel B-cell lymphoma (Bcl)-2 monoclonal antibody-functionalized USPIO nanoparticle coated with an amphiphilic polymer (carboxylated polyethylene glycol monooleyl ether [OE-PEG-COOH]). These nanoparticles can be effectively internalized by beta cells and label primary islet cells, at relatively low iron concentration. The biocompatibility and cytotoxicity of these products were investigated by comparison with the commercial USPIO product, FeraSpin^™ S. We also assessed the safe dosage range of the product. Although some cases showed a hypointensity change at the site of transplant, a strong magnetic resonance imaging (MRI) was detectable by a clinical MRI scanner, at field strength of 3.0 Tesla, in vivo, and the iron deposition/attached in islets was confirmed by Prussian blue and immunohistochemistry staining. It is noteworthy that based on our synthesis approach, in future, we could exchange the Bcl-2 with other probes that would be more specific for the targeted cells and that would have better labeling specificity in vivo. The combined results point to the promising potential of the novel Bcl-2-functionalized PEG-USPIO as a molecular imaging agent for in vivo monitoring of islet cells or other cells.

Image guided biodistribution and pharmacokinetic studies of theranostics

Image guided technique is playing an increasingly important role in the investigation of the biodistribution and pharmacokinetics of drugs or drug delivery systems in various diseases, especially cancers. Besides anatomical imaging modalities such as computed tomography (CT), magnetic resonance imaging (MRI), molecular imaging strategy including optical imaging, positron emission tomography (PET) and single-photon emission computed tomography (SPECT) will facilitate the localization and quantization of radioisotope or optical probe labeled nanoparticle delivery systems in the category of theranostics. The quantitative measurement of the bio-distribution and pharmacokinetics of theranostics in the fields of new drug/probe development, diagnosis and treatment process monitoring as well as tracking the brain-blood-barrier (BBB) breaking through by high sensitive imaging method, and the applications of the representative imaging modalities are summarized in this review.