Histological study of the biodynamics of iron oxide nanoparticles with different diameters

Pharmacokinetics of magnetic iron oxide nanoparticles for medical applications

Magnetic iron oxide nanoparticles (MNPs) have been under intense investigation for at least the last five decades as they show enormous potential for many biomedical applications, such as biomolecule separation, MRI imaging and hyperthermia. Moreover, a large area of research on these nanostructures is concerned with their use as carriers of drugs, nucleic acids, peptides and other biologically active compounds, often leading to the development of targeted therapies. The uniqueness of MNPs is due to their nanometric size and unique magnetic properties. In addition, iron ions, which, along with oxygen, are a part of the MNPs, belong to the trace elements in the body. Therefore, after digesting MNPs in lysosomes, iron ions are incorporated into the natural circulation of this element in the body, which reduces the risk of excessive storage of nanoparticles. Still, one of the key issues for the therapeutic applications of magnetic nanoparticles is their pharmacokinetics which is reflected in the circulation time of MNPs in the bloodstream. These characteristics depend on many factors, such as the size and charge of MNPs, the nature of the polymers and any molecules attached to their surface, and other. Since the pharmacokinetics depends on the resultant of the physicochemical properties of nanoparticles, research should be carried out individually for all the nanostructures designed. Almost every year there are new reports on the results of studies on the pharmacokinetics of specific magnetic nanoparticles, thus it is very important to follow the achievements on this matter. This paper reviews the latest findings in this field. The mechanism of action of the mononuclear phagocytic system and the half-lives of a wide range of nanostructures are presented. Moreover, factors affecting clearance such as hydrodynamic and core size, core morphology and coatings molecules, surface charge and technical aspects have been described.

Targeted Nanoparticles with High Heating Efficiency for the Treatment of Endometriosis with Systemically Delivered Magnetic Hyperthermia

Endometriosis is a devastating disease in which endometrial-like tissue forms lesions outside the uterus. It causes infertility and severe pelvic pain in ≈176 million women worldwide, and there is currently no cure for this disease. Magnetic hyperthermia could potentially eliminate widespread endometriotic lesions but has not previously been considered for treatment because conventional magnetic nanoparticles have relatively low heating efficiency and can only provide ablation temperatures (>46 °C) following direct intralesional injection. This study is the first to describe nanoparticles that enable systemically delivered magnetic hyperthermia for endometriosis treatment. When subjected to an alternating magnetic field (AMF), these hexagonal iron-oxide nanoparticles exhibit extraordinary heating efficiency that is 6.4× greater than their spherical counterparts. Modifying nanoparticles with a peptide targeted to vascular endothelial growth factor receptor 2 (VEGFR-2) enhances their endometriosis specificity. Studies in mice bearing transplants of macaque endometriotic tissue reveal that, following intravenous injection at a low dose (3 mg per kg), these nanoparticles efficiently accumulate in endometriotic lesions, selectively elevate intralesional temperature above 50 °C upon exposure to external AMF, and completely eradicate them with a single treatment. These nanoparticles also demonstrate promising potential as magnetic resonance imaging (MRI) contrast agents for precise detection of endometriotic tissue before AMF application.

In Vivo Distribution of Poly(ethylene glycol) Functionalized Iron Oxide Nanoclusters: An Ultrastructural Study

The in vivo distribution of 50 nm clusters of polyethylene glycol-conjugated superparamagnetic iron oxide nanoparticles (SPIONs-PEG) was conducted in this study. SPIONs-PEG were synthesized de novo, and their structure and paramagnetic behaviors were analyzed by specific methods (TEM, DLS, XRD, VSM). Wistar rats were treated with 10 mg Fe/kg body weight SPIONs-PEG and their organs and blood were examined at two intervals for short-term (15, 30, 60, 180 min) and long-term (6, 12, 24 h) exposure evaluation. Most exposed organs were investigated through light and transmission electron microscopy, and blood and urine samples were examined through fluorescence spectrophotometry. SPIONs-PEG clusters entered the bloodstream after intraperitoneal and intravenous administrations and ended up in the urine, with the highest clearance at 12 h. The skin and spleen were within normal histological parameters, while the liver, kidney, brain, and lungs showed signs of transient local anoxia or other transient pathological affections. This study shows that once internalized, the synthesized SPIONs-PEG disperse well through the bloodstream with minor to nil induced tissue damage, are biocompatible, have good clearance, and are suited for biomedical applications.

Organ Metallome Processed with Chemometric Methods Enable the Determination of Elements that May Serve as Markers of Exposure to Iron Oxide Nanoparticles in Male Rats

The systemic influence of iron oxide nanoparticles on the elemental homeostasis of key organs was examined in male rats. In tissues taken at different intervals from nanoparticles injection, the dynamics of elemental changes was analyzed. The organ metallome was studied using total reflection X-ray fluorescence. The obtained data were processed with advanced cluster and discriminant analyses-to classify the tissues according to their organs of origin and to distinguish accurately the nanoparticle-treated and normal rats. Additionally, in the case of liver and heart, it was possible to determine the elements of highest significance for different treatments, which may serve as markers of exposure to iron oxide nanoparticles.

Introducing Specificity to Iron Oxide Nanoparticle Imaging by Combining 57Fe-Based MRI and Mass Spectrometry

Iron oxide nanoparticles (ION) are highly sensitive probes for magnetic resonance imaging (MRI) that have previously been used for in vivo cell tracking and have enabled implementation of several diagnostic tools to detect and monitor disease. However, the in vivo MRI signal of ION can overlap with the signal from endogenous iron, resulting in a lack of detection specificity. Therefore, the long-term fate of administered ION remains largely unknown, and possible tissue deposition of iron cannot be assessed with established methods. Herein, we combine nonradioactive ⁵⁷Fe-ION MRI with ex vivo laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) imaging, enabling unambiguous differentiation between endogenous iron (⁵⁶Fe) and iron originating from applied ION in mice. We establish ⁵⁷Fe-ION as an in vivo MRI sensor for cell tracking in a mouse model of subcutaneous inflammation and for assessing the long-term fate of ⁵⁷Fe-ION. Our approach resolves the lack of detection specificity in ION imaging by unambiguously recording a ⁵⁷Fe signature.

MR signal changes in superparamagnetic iron oxide nanoparticle-labeled macrophages in response to X irradiation

To investigate whether MR signals associated with macrophages labeled with superparamagnetic iron oxide nanoparticles (SPIONs) change in response to X irradiation, we performed in vitro MRI of SPION-labeled macrophage-like J774A.1 cells that were subsequently X irradiated. We labeled the cells with ferucarbotran at a concentration of 10 μg iron/mL in culture medium for 16 h and subsequently performed X irradiation at doses of 0, 2, 10, or 20 Gy using a low-energy X-ray unit. On Days 3 and 6, we suspended the cells in agar at a concentration of 2 × 10⁶ cells/mL and acquired multi-gradient echo and multi-spin echo images of the cell samples using a 3 T scanner to estimate R₂ * and R₂ . In addition, we microscopically investigated the relationship among the MR signal changes, intracellular SPIONs, and acidic organelles. Our data showed that X irradiation of labeled cells caused increased SPION deposition in lysosomes compared with the non-irradiated control. On Day 3, R₂ * and R₂ values in the 0 to 10 Gy irradiated samples were dose-dependently increased 5.4- and 1.5-fold compared with 17 ± 2 and 13 ± 1/s, respectively, in the non-irradiated control; these values plateaued at more than 10 Gy. Although the increases in R₂ *, R₂ , and SPION deposition were still observed in the 10 and 20 Gy samples on Days 6 and 7, the 2 Gy samples showed recovery in these parameters as cell growth was restored. Acidic organelles were temporarily increased in the irradiated cells, which suggests that the reduction in lysosomal acidity was not attributable to SPION deposition. In conclusion, X irradiation of macrophages can cause SPION deposition and R₂ * and R₂ elevation in a specific dose range. MRI of SPION-labeled and subsequently X-irradiated macrophages may be utilized as a novel technique for investigating macrophage responses to X irradiation.

Antimicrobial magnetic nanoparticles based-therapies for controlling infectious diseases

In the last years, the antimicrobial resistance against antibiotics has become a serious health issue, arise as global threat. This has generated a search for new strategies in the progress of new antimicrobial therapies. In this context, different nanosystems with antimicrobial properties have been studied. Specifically, magnetic nanoparticles seem to be very attractive due to their relatively simple synthesis, intrinsic antimicrobial activity, low toxicity and high versatility. Iron oxide NPs (IONPs) was authorized by the World Health Organization for human used in biomedical applications such as in vivo drug delivery systems, magnetic guided therapy and contrast agent for magnetic resonance imaging have been widely documented. Furthermore, the antimicrobial activity of different magnetic nanoparticles has recently been demonstrated. This review elucidates the recent progress of IONPs in drug delivery systems and focuses on the treatment of infectious diseases and target the possible detrimental biological effects and associated safety issues.

Advantages and Limitations of Current Techniques for Analyzing the Biodistribution of Nanoparticles

Nanomedicines are typically submicrometer-sized carrier materials (nanoparticles) encapsulating therapeutic and/or imaging compounds that are used for the prevention, diagnosis and treatment of diseases. They are increasingly being used to overcome biological barriers in the body to improve the way we deliver compounds to specific tissues and organs. Nanomedicine technology aims to improve the balance between the efficacy and the toxicity of therapeutic compounds. Nanoparticles, one of the key technologies of nanomedicine, can exhibit a combination of physical, chemical and biological characteristics that determine their in vivo behavior. A key component in the translational assessment of nanomedicines is determining the biodistribution of the nanoparticles following in vivo administration in animals and humans. There are a range of techniques available for evaluating nanoparticle biodistribution, including histology, electron microscopy, liquid scintillation counting (LSC), indirectly measuring drug concentrations, in vivo optical imaging, computed tomography (CT), magnetic resonance imaging (MRI), and nuclear medicine imaging. Each technique has its own advantages and limitations, as well as capabilities for assessing real-time, whole-organ and cellular accumulation. This review will address the principles and methodology of each technique and their advantages and limitations for evaluating in vivo biodistribution of nanoparticles.

Magnetic particle imaging: kinetics of the intravascular signal in vivo

BACKGROUND

Magnetic particle imaging (MPI) uses magnetic fields to visualize superparamagnetic iron oxide nanoparticles (SPIO). Today, Resovist(®) is still the reference SPIO for MPI. The objective of this study was to evaluate the in vivo blood half-life of two different types of Resovist (one from Bayer Pharma AG, and one from I'rom Pharmaceutical Co Ltd) in MPI.

METHODS

A Resovist concentration of 50 μmol/kg was injected into the ear artery of ten New Zealand White rabbits. Five animals received Resovist distributed by I'rom Pharmaceutical Co Ltd and five received Resovist by Bayer Pharma AG. Blood samples were drawn before and directly after injection of Resovist, at 5, 10, and 15 minutes, and then every 15 minutes until 120 minutes after the injection. The MPI signal of the blood samples was evaluated using magnetic particle spectroscopy.

RESULTS

The average decline of the blood MPI signal from the two distributions differed significantly (P=0.0056). Resovist distributed by Bayer Pharma AG showed a slower decline of the MPI signal (39.7% after 5 minutes, 20.5% after 10 minutes, and 12.1% after 15 minutes) compared with Resovist produced by I'rom Pharmaceutical Co Ltd (20.4% after 5 minutes, 7.8% after 10 minutes, no signal above noise level after 15 minutes).

CONCLUSION

In MPI, the blood half-life of an SPIO tracer cannot be equalized to the blood half-life of its MPI signal. Resovist shows a very rapid decline of blood MPI signal and is thus not suitable as a long circulating tracer. For cardiovascular applications in MPI, it may be used as a bolus tracer.

A noninvasive method to determine the fate of Fe(3)O(4) nanoparticles following intravenous injection using scanning SQUID biosusceptometry

Magnetic nanoparticles (MNPs) of Fe₃O₄ have been widely applied in many medical fields, but few studies have clearly shown the outcome of particles following intravenous injection. We performed a magnetic examination using scanning SQUID biosusceptometry (SSB). Based on the results of SSB analysis and those of established in vitro nonmagnetic bioassays, this study proposes a model of MNP metabolism consisting of an acute metabolic phase with an 8 h duration that is followed by a chronic metabolic phase that continues for 28 d following MNP injection. The major features included the delivery of the MNPs to the heart and other organs, the biodegradation of the MNPs in organs rich with macrophages, the excretion of iron metabolites in the urine, and the recovery of the iron load from the liver and the spleen. Increases in serum iron levels following MNP injection were accompanied by increases in the level of transferrin in the serum and the number of circulating red blood cells. Correlations between the in vivo and in vitro test results indicate the feasibility of using SSB examination for the measurement of MNP concentrations, implying future clinical applications of SSB for monitoring the hematological effects of MNP injection.

In vivo screening of hepatocellular carcinoma using AC susceptibility of anti-alpha fetoprotein-activated magnetic nanoparticles

With antibody-mediated magnetic nanoparticles (MNPs) applied in cancer examinations, patients must pay at least twice for MNP reagents in immunomagnetic reduction (IMR) of in vitro screening and magnetic resonance imaging (MRI) of in vivo tests. This is because the high maintenance costs and complex analysis of MRI have limited the possibility of in vivo screening. Therefore, this study proposes novel methods for in vivo screening of tumors by examining the AC susceptibility of bound MNPs using scanning superconducting-quantum-interference-device (SQUID) biosusceptometry (SSB), thereby demonstrating high portability and improved economy. The favorable agreement between in vivo tests using SSB and MRI demonstrated the feasibility of in vivo screening using SSB for hepatocellular carcinoma (HCC) targeted by anti-alpha fetoprotein (AFP)-mediated MNPs. The magnetic labeling was also proved by in vitro tests using SSB and biopsy assays. Therefore, patients receiving bioprobe-mediated MNPs only once can undergo in vivo screening using SSB in the future.

Personalized nanomedicine advancements for stem cell tracking

Recent technological developments in biomedicine have facilitated the generation of data on the anatomical, physiological and molecular level for individual patients and thus introduces opportunity for therapy to be personalized in an unprecedented fashion. Generation of patient-specific stem cells exemplifies the efforts toward this new approach. Cell-based therapy is a highly promising treatment paradigm; however, due to the lack of consistent and unbiased data about the fate of stem cells in vivo, interpretation of therapeutic effects remains challenging hampering the progress in this field. The advent of nanotechnology with a wide palette of inorganic and organic nanostructures has expanded the arsenal of methods for tracking transplanted stem cells. The diversity of nanomaterials has revolutionized personalized nanomedicine and enables individualized tailoring of stem cell labeling materials for the specific needs of each patient. The successful implementation of stem cell tracking will likely be a significant driving force that will contribute to the further development of nanotheranostics. The purpose of this review is to emphasize the role of cell tracking using currently available nanoparticles.

Negatively charged superparamagnetic iron oxide nanoparticles: a new blood-pooling magnetic resonance contrast agent

PURPOSE

Our purpose was to investigate the utility of superparamagnetic iron-oxide nanoparticles (SPIO) as a blood-pooling contrast agent at magnetic resonance imaging (MRI).

MATERIALS AND METHODS

We studied four contrast agents: carboxymethyl-diethylaminoethyl dextran magnetite SPIO (CMEADM-S, diameter 54 nm), negatively charged CMEADM ultrasmall SPIO (CMEADM-U, 32 nm), alkali-treated dextran magnetite SPIO (ATDM-S, 55 nm), and ATDM ultrasmall SPIO (ATDM-U, 28 nm) carrying a neutral charge. Each contrast agent (80 μmol/kg) was injected intraperitoneally into apolipoprotein E (apoE) mice and the tissue iron concentration was measured 30-, 60-, 180-, and 300-min later by nuclear MR. For MR angiographic (MRA) evaluation, we injected the agents into the auricular vein of four groups of 15 rabbits. Immediately and 30-, 60-, 180-, and 300-min later, three rabbits from each group were subjected to MRI. The organ/background signal ratio (SR) was calculated. Statistical analyses were performed with Tukey's honestly significant difference (HSD) test.

RESULTS

At 60 and 180 min, blood-iron concentration of CMEADM-U was significantly different from other contrast agents. In the abdominal aorta and inferior vena cava, SR of CMEADM-U was higher at 180 and 300 min than of the other contrast agents. In the thoracic aorta, there was no difference in SR at 300 min between CMEADM-U and CMEADM-S.

CONCLUSION

Negatively charged SPIO nanoparticles may be useful as a blood-pooling contrast agent.

Ferumoxytol: a silver lining in the treatment of anemia of chronic kidney disease or another dark cloud?

Intravenous iron therapy is pivotal in the treatment of anemia of chronic kidney disease to optimize the response of hemoglobin to erythropoiesis-stimulating agents. Intravenous iron use in patients with chronic kidney disease is on the rise. Recent clinical trial data prompting safety concerns regarding the use of erythropoiesis-stimulating agents has stimulated new US Food and Drug Administration label changes and restrictions for these agents, and has encouraged more aggressive use of intravenous iron. The currently available intravenous iron products differ with regard to the stability of the iron-carbohydrate complex and potential to induce hypersensitivity reactions. Ferumoxytol is a newer large molecular weight intravenous iron formulation that is a colloidal iron oxide nanoparticle suspension coated with polyglucose sorbitol carboxymethyl ether. Ferumoxytol has robust iron-carbohydrate complex stability with minimal dissociation or appearance of free iron in the serum, allowing the drug to be given in relatively large doses with a rapid rate of administration. Clinical trials have demonstrated the superior efficacy of ferumoxytol versus oral iron with minimal adverse effects. However, recent postmarketing data have demonstrated a risk of hypersensitivity that has prompted new changes to the product information mandated by the Food and Drug Administration. Additionally, the long-term safety of this agent has not been evaluated, and its place in the treatment of anemia of chronic kidney disease has not been fully elucidated.

Intravenous ferumoxytol allows noninvasive MR imaging monitoring of macrophage migration into stem cell transplants

PURPOSE

To develop a clinically applicable imaging technique for monitoring differential migration of macrophages into viable and apoptotic matrix-associated stem cell implants (MASIs) in arthritic knee joints.

MATERIALS AND METHODS

With institutional animal care and use committee approval, six athymic rats were injected with intravenous ferumoxytol (0.5 mmol iron per kilogram of body weight) to preload macrophages of the reticuloendothelial system with iron oxide nanoparticles. Forty-eight hours later, all animals received MASIs of viable adipose-derived stem cells (ADSCs) in an osteochondral defect of the right femur and mitomycin-pretreated apoptotic ADSCs in an osteochondral defect of the left femur. One additional control animal each received intravenous ferumoxytol and bilateral scaffold-only implants (without cells) or bilateral MASIs without prior ferumoxytol injection. All knees were imaged with a 7.0-T magnetic resonance (MR) imaging unit with T2-weighted fast spin-echo sequences immediately after, as well as 2 and 4 weeks after, matrix-associated stem cell implantation. Signal-to-noise ratios (SNRs) of viable and apoptotic MASIs were compared by using a linear mixed-effects model. MR imaging data were correlated with histopathologic findings.

RESULTS

All ADSC implants showed a slowly decreasing T2 signal over 4 weeks after matrix-associated stem cell implantation. SNRs decreased significantly over time for the apoptotic implants (SNRs on the day of matrix-associated stem cell implantation, 2 weeks after the procedure, and 4 weeks after the procedure were 16.9, 10.9, and 6.7, respectively; P = .0004) but not for the viable implants (SNRs on the day of matrix-associated stem cell implantation, 2 weeks after the procedure, and 4 weeks after the procedure were 17.7, 16.2, and 15.7, respectively; P = .2218). At 4 weeks after matrix-associated stem cell implantation, SNRs of apoptotic ADSCs were significantly lower than those of viable ADSCs (mean, 6.7 vs 15.7; P = .0013). This corresponded to differential migration of iron-loaded macrophages into MASIs.

CONCLUSION

Iron oxide loading of macrophages in the reticuloendothelial system by means of intravenous ferumoxytol injection can be utilized to monitor differential migration of bone marrow macrophages into viable and apoptotic MASIs in a rat model.