Magnetoferritin: characterization of a novel superparamagnetic MR contrast agent

Gastric stability of bare and chitosan-fabricated ferritin and its bio-mineral: implication for potential dietary iron supplements

Iron deficiency anaemia (IDA), the most widespread nutritional disorder, is a persistent global health issue affecting millions, especially in resource-limited geographies. Oral iron supplementation is usually the first choice for exogenous iron administration owing to its convenience, effectiveness and low cost. However, commercially available iron supplementations are often associated with oxidative stress, gastrointestinal side effects, infections and solubility issues. Herein, we aim to address these limitations by employing ferritin proteins-self-assembled nanocaged architectures functioning as a soluble cellular iron repository-as a non-toxic and biocompatible alternative. Our in vitro studies based on PAGE and TEM indicate that bare ferritin proteins are resistant to gastric conditions but their cage integrity is compromised under longer incubation periods and at higher concentrations of pepsin, which is a critical component of gastric juice. To ensure the safe delivery of encapsulated iron cargo, with minimal cage disintegration/degradation and iron leakage along the gastrointestinal tract, we fabricated the surface of ferritin with chitosan. Further, the stoichiometry and absorptivity of iron-chelator complexes at both gastric and circumneutral pH were estimated using Job's plot. Unlike bipyridyl, deferiprone exhibited pH dependency. In vitro kinetics was studied to evaluate iron release from bare and chitosan-fabricated ferritins employing both reductive (in the presence of ascorbate and bipyridyl) and non-reductive (direct chelation by deferiprone) pathways to determine their bio-mineral stabilities. Chitosan-decorated ferritin displayed superior cage integrity and iron retention capability over bare ferritin in simulated gastric fluid. The ability of ferritins to naturally facilitate controlled iron release in conjugation with enteric coating provided by chitosan may mitigate the aforementioned side effects and enhance iron absorption in the intestine. The results of the current study could pave the way for the development of an oral formulation based on ferritin-caged iron bio-mineral that can be a promising alternative for the treatment of IDA, offering better therapeutic outcomes.

In Vivo Cellular Magnetic Imaging: Labeled vs. Unlabeled Cells

Superparamagnetic iron oxide (SPIO)-labeling of cells has been applied for magnetic resonance imaging (MRI) cell tracking for over 30 years, having resulted in a dozen or so clinical trials. SPIO nanoparticles are biodegradable and can be broken down into elemental iron, and hence the tolerance of cells to magnetic labeling has been overall high. Over the years, however, single reports have accumulated demonstrating that the proliferation, migration, adhesion and differentiation of magnetically labeled cells may differ from unlabeled cells, with inhibition of chondrocytic differentiation of labeled human mesenchymal stem cells (hMSCs) as a notable example. This historical perspective provides an overview of some of the drawbacks that can be encountered with magnetic labeling. Now that magnetic particle imaging (MPI) cell tracking is emerging as a new in vivo cellular imaging modality, there has been a renaissance in the formulation of SPIO nanoparticles this time optimized for MPI. Lessons learned from the occasional past pitfalls encountered with SPIO-labeling of cells for MRI may expedite possible future clinical translation of (combined) MRI/MPI cell tracking.

Destruction of Lysozyme Amyloid Fibrils Induced by Magnetoferritin and Reconstructed Ferritin

Neurodegenerative disorders, including Alzheimer's disease (AD), Parkinson's disease (PD), or systemic amyloidosis, are characterized by the specific protein transformation from the native state to stable insoluble deposits, e.g., amyloid plaques. The design of potential therapeutic agents and drugs focuses on the destabilization of the bonds in their beta-rich structures. Surprisingly, ferritin derivatives have recently been proposed to destabilize fibril structures. Using atomic force microscopy (AFM) and fluorescence spectrophotometry, we confirmed the destructive effect of reconstructed ferritin (RF) and magnetoferritin (MF) on lysosome amyloid fibrils (LAF). The presence of iron was shown to be the main factor responsible for the destruction of LAF. Moreover, we found that the interaction of RF and MF with LAF caused a significant increase in the release of potentially harmful ferrous ions. Zeta potential and UV spectroscopic measurements of LAF and ferritin derivative mixtures revealed a considerable difference in RF compared to MF. Our results contribute to a better understanding of the mechanism of fibril destabilization by ferritin-like proteins. From this point of view, ferritin derivatives seem to have a dual effect: therapeutic (fibril destruction) and adverse (oxidative stress initiated by increased Fe²⁺ release). Thus, ferritins may play a significant role in various future biomedical applications.

Designing Protein-Based Probes for Sensing Biological Analytes with Magnetic Resonance Imaging

Genetically encoded sensors provide unique advantages for monitoring biological analytes with molecular and cellular-level specificity. While sensors derived from fluorescent proteins represent staple tools in biological imaging, these probes are limited to optically accessible preparations owing to physical curbs on light penetration. In contrast to optical methods, magnetic resonance imaging (MRI) may be used to noninvasively look inside intact organisms at any arbitrary depth and over large fields of view. These capabilities have spurred the development of innovative methods to connect MRI readouts with biological targets using protein-based probes that are in principle genetically encodable. Here, we highlight the state-of-the-art in MRI-based biomolecular sensors, focusing on their physical mechanisms, quantitative characteristics, and biological applications. We also describe how innovations in reporter gene technology are creating new opportunities to engineer MRI sensors that are sensitive to dilute biological targets.

Biomimetic Nanomaterials Triggered Ferroptosis for Cancer Theranostics

Ferroptosis, as a recently discovered non-apoptotic programmed cell death with an iron-dependent form, has attracted great attention in the field of cancer nanomedicine. However, many ferroptosis-related nano-inducers encountered unexpected limitations such as immune exposure, low circulation time, and ineffective tumor targeting. Biomimetic nanomaterials possess some unique physicochemical properties which can achieve immune escape and effective tumor targeting. Especially, certain components of biomimetic nanomaterials can further enhance ferroptosis. Therefore, this review will provide a comprehensive overview on recent developments of biomimetic nanomaterials in ferroptosis-related cancer nanomedicine. First, the definition and character of ferroptosis and its current applications associated with chemotherapy, radiotherapy, and immunotherapy for enhancing cancer theranostics were briefly discussed. Subsequently, the advantages and limitations of some representative biomimetic nanomedicines, including biomembranes, proteins, amino acids, polyunsaturated fatty acids, and biomineralization-based ferroptosis nano-inducers, were further spotlighted. This review would therefore help the spectrum of advanced and novice researchers who are interested in this area to quickly zoom in the essential information and glean some provoking ideas to advance this subfield in cancer nanomedicine.

Blocking effect of ferritin on the ryanodine receptor-isoform 2

Iron, an essential element for most living organism, participates in a wide variety of physiological processes. Disturbance in iron homeostasis has been associated with numerous pathologies, particularly in the heart and brain, which are the most susceptible organs. Under iron-overload conditions, the generation of reactive oxygen species leads to impairment in Ca2+ signaling, fundamentally implicated in cardiac and neuronal physiology. Since iron excess is accompanied by increased expression of iron-storage protein, ferritin, we examined whether ferritin has an effect on the ryanodine receptor - isoform 2 (RYR2), which is one of the major components of Ca2+ signaling. Using the method of planar lipid membranes, we show that ferritin induced an abrupt, permanent blockage of the RYR2 channel. The ferritin effect was strongly voltage dependent and competitively antagonized by cytosolic TEA+, an impermeant RYR2 blocker. Our results collectively indicate that monomeric ferritin highly likely blocks the RYR2 channel by a direct electrostatic interaction within the wider region of the channel permeation pathway.

Longitudinal and Transverse Relaxivity Analysis of Native Ferritin and Magnetoferritin at 7 T MRI

Magnetite mineralization in human tissue is associated with various pathological processes, especially neurodegenerative disorders. Ferritin’s mineral core is believed to be a precursor of magnetite mineralization. Magnetoferritin (MF) was prepared with different iron loading factors (LFs) as a model system for pathological ferritin to analyze its MRI relaxivity properties compared to those of native ferritin (NF). The results revealed that MF differs statistically significantly from NF, with the same LF, for all studied relaxation parameters at 7 T: r₁, r₂, r₂*, r₂/r₁, r₂*/r₁. Distinguishability of MF from NF may be useful in non-invasive MRI diagnosis of pathological processes associated with iron accumulation and magnetite mineralization (e.g., neurodegenerative disorders, cancer, and diseases of the heart, lung and liver). In addition, it was found that MF samples possess very strong correlation and MF’s relaxivity is linearly dependent on the LF, and the transverse and longitudinal ratios r₂/r₁ and r₂*/r₁ possess complementary information. This is useful in eliminating false-positive hypointensive artefacts and diagnosis of the different stages of pathology. These findings could contribute to the exploitation of MRI techniques in the non-invasive diagnosis of iron-related pathological processes in human tissue.

Clinical therapies and nano drug delivery systems for urinary bladder cancer

Bladder cancer is the 10^th most commonly occurring malignancy worldwide with a 75% of 5-year survival rate, while it ranks 13^th among the deaths occurring due to cancer. The majority of bladder cancer cases are diagnosed at an early stage and 70% are of non-invasive grade. However, 70% of these cases develop chemoresistance and progress to the muscle invasive stage. Conventional chemotherapy treatments are unsuccessful in curbing chemoresistance, bladder cancer progression while having an adverse side effect, which is mainly due to off-target drug distribution. Therefore, new drug delivery strategies, new therapeutics and therapies or their combination are being explored to develop better treatments. In this regard, nanotechnology has shown promise in the targeted delivery of therapeutics to bladder cancer cells. This review discusses the recent discovery of new therapeutics (chemotherapeutics, immunotherapeutic, and gene therapies), recent developments in the delivery of therapeutics using nano drug delivery systems, and the combination treatments with FDA-approved therapies, i.e., hyperthermia and photodynamic therapy. We also discussed the potential of other novel drug delivery systems that are minimally explored in bladder cancer. Lastly, we discussed the clinical status of therapeutics and therapies for bladder cancer. Overall, this review can provide a summary of available treatments for bladder cancer, and also provide opportunities for further development of drug delivery systems for better management of bladder cancer.

New imaging tools to measure nephron number in vivo: opportunities for developmental nephrology

The mammalian kidney is a complex organ, requiring the concerted function of up to millions of nephrons. The number of nephrons is constant after nephrogenesis during development, and nephron loss over a life span can lead to susceptibility to acute or chronic kidney disease. New technologies are under development to count individual nephrons in the kidney in vivo. This review outlines these technologies and highlights their relevance to studies of human renal development and disease.

Possible magneto-mechanical and magneto-thermal mechanisms of ion channel activation in magnetogenetics

The palette of tools for perturbation of neural activity is continually expanding. On the forefront of this expansion is magnetogenetics, where ion channels are genetically engineered to be closely coupled to the iron-storage protein ferritin. Initial reports on magnetogenetics have sparked a vigorous debate on the plausibility of physical mechanisms of ion channel activation by means of external magnetic fields. The criticism leveled against magnetogenetics as being physically implausible is based on the specific assumptions about the magnetic spin configurations of iron in ferritin. I consider here a wider range of possible spin configurations of iron in ferritin and the consequences these might have in magnetogenetics. I propose several new magneto-mechanical and magneto-thermal mechanisms of ion channel activation that may clarify some of the mysteries that presently challenge our understanding of the reported biological experiments. Finally, I present some additional puzzles that will require further theoretical and experimental investigation.

Magnetoferritin: Process, Prospects, and Their Biomedical Applications

Ferritin is a spherical iron storage protein composed of 24 subunits and an iron core. Using biomimetic mineralization, magnetic iron oxide can be synthesized in the cavity of ferritin to form magnetoferritin (MFt). MFt, also known as a superparamagnetic protein, is a novel magnetic nanomaterial with good biocompatibility and flexibility for biomedical applications. Recently, it has been demonstrated that MFt had tumor targetability and a peroxidase-like catalytic activity. Thus, MFt, with its many unique properties, provides a powerful platform for tumor diagnosis and therapy. In this review, we discuss the biomimetic synthesis and biomedical applications of MFt.

Application of cationized magnetoferritin for magnetic field-assisted delivery of short interfering RNA in vitro

Cationized magnetoferritin is used for development of a simple, efficient, and fast delivery of short interference RNA into cells using combination of magnetophoresis for pre-concentration of siRNA-magnetoferritin complex on the surface of plated cells with subsequent application of nanosecond laser pulses producing stress waves in transfection chamber, which permeabilize cell membrane for the facilitated delivery of siRNA into the cell interior. As has been quantified using siRNA inducing cell death assay, by combination of these two physical factors we have obtained high efficiency for tested three different human carcinoma cells. Proposed method of gene silencing based on cationized magnetoferritin is a versatile and easily accessible platform with many possible applications in gene therapy.

Biomolecular MRI reporters: Evolution of new mechanisms

Magnetic resonance imaging (MRI) is a powerful technique for observing the function of specific cells and molecules inside living organisms. However, compared to optical microscopy, in which fluorescent protein reporters are available to visualize hundreds of cellular functions ranging from gene expression and chemical signaling to biomechanics, to date relatively few such reporters are available for MRI. Efforts to develop MRI-detectable biomolecules have mainly focused on proteins transporting paramagnetic metals for T1 and T2 relaxation enhancement or containing large numbers of exchangeable protons for chemical exchange saturation transfer. While these pioneering developments established several key uses of biomolecular MRI, such as imaging of gene expression and functional biosensing, they also revealed that low molecular sensitivity poses a major challenge for broader adoption in biology and medicine. Recently, new classes of biomolecular reporters have been developed based on alternative contrast mechanisms, including enhancement of spin diffusivity, interactions with hyperpolarized nuclei, and modulation of blood flow. These novel reporters promise to improve sensitivity and enable new forms of multiplexed and functional imaging.

Functional ferritin nanoparticles for biomedical applications

Ferritin, a major iron storage protein with a hollow interior cavity, has been reported recently to play many important roles in biomedical and bioengineering applications. Owing to the unique architecture and surface properties, ferritin nanoparticles offer favorable characteristics and can be either genetically or chemically modified to impart functionalities to their surfaces, and therapeutics or probes can be encapsulated in their interiors by controlled and reversible assembly/disassembly. There has been an outburst of interest regarding the employment of functional ferritin nanoparticles in nanomedicine. This review will highlight the recent advances in ferritin nanoparticles for drug delivery, bioassay, and molecular imaging with a particular focus on their biomedical applications.

Engineered ferritin nanocages as natural contrast agents in magnetic resonance imaging

Here we report the development of a “natural” MRI contrast agent with tunable Fe loading and a magnetic core for magnetic resonance imaging.

Biocompatibility of ferritin-based nanoparticles as targeted MRI contrast agents

Ferritin is a naturally occurring iron storage protein, proposed as a clinically relevant nanoparticle with applications as a diagnostic and therapeutic agent. Cationic ferritin is a targeted, injectable contrast agent to measure kidney microstructure with MRI. Here, the toxicity of horse spleen ferritin is assessed as a step to clinical translation. Adult male mice received cationic, native and high dose cationic ferritin (CF, NF, or HDCF) or saline and were monitored for 3weeks. Transient weight loss occurred in the ferritin groups with no difference in renal function parameters. Ferritin-injected mice demonstrated a lower serum iron 3weeks after administration. In ferritin-injected animals pre-treated with hydrocortisone, there were no structural or weight differences in the kidneys, liver, lung, heart, or spleen. This study demonstrates a lack of significant detrimental effects of horse-derived ferritin-based nanoparticles at MRI-detectable doses, allowing further exploration of these agents in basic research and clinical diagnostics.

Ultra-fast stem cell labelling using cationised magnetoferritin

Magnetic cell labelling with superparamagnetic iron oxide nanoparticles (SPIONs) facilitates many important biotechnological applications, such as cell imaging and remote manipulation. However, to achieve adequate cellular loading of SPIONs, long incubation times (24 hours and more) or laborious surface functionalisation are often employed, which can adversely affect cell function. Here, we demonstrate that chemical cationisation of magnetoferritin produces a highly membrane-active nanoparticle that can magnetise human mesenchymal stem cells (hMSCs) using incubation times as short as one minute. Magnetisation persisted for several weeks in culture and provided significant T2* contrast enhancement during magnetic resonance imaging. Exposure to cationised magnetoferritin did not adversely affect the membrane integrity, proliferation and multi-lineage differentiation capacity of hMSCs, which provides the first detailed evidence for the biocompatibility of magnetoferritin. The combination of synthetic ease and flexibility, the rapidity of labelling and absence of cytotoxicity make this novel nanoparticle system an easily accessible and versatile platform for a range of cell-based therapies in regenerative medicine.

Visualization and quantification of simian immunodeficiency virus-infected cells using non-invasive molecular imaging

In vivo imaging can provide real-time information and three-dimensional (3D) non-invasive images of deep tissues and organs, including the brain, whilst allowing longitudinal observation of the same animals, thus eliminating potential variation between subjects. Current in vivo imaging technologies, such as magnetic resonance imaging (MRI), positron emission tomography-computed tomography (PET-CT) and bioluminescence imaging (BLI), can be used to pinpoint the spatial location of target cells, which is urgently needed for revealing human immunodeficiency virus (HIV) dissemination in real-time and HIV-1 reservoirs during suppressive antiretroviral therapy (ART). To demonstrate that in vivo imaging can be used to visualize and quantify simian immunodeficiency virus (SIV)-transduced cells, we genetically engineered SIV to carry different imaging reporters. Based on the expression of the reporter genes, we could visualize and quantify the SIV-transduced cells via vesicular stomatitis virus glycoprotein pseudotyping in a mouse model using BLI, PET-CT or MRI. We also engineered a chimeric EcoSIV for in vivo infection study. Our results demonstrated that BLI is sensitive enough to detect as few as five single cells transduced with virus, whilst PET-CT can provide 3D images of the spatial location of as few as 10 000 SIV-infected cells. We also demonstrated that MRI can provide images with high spatial resolution in a 3D anatomical context to distinguish a small population of SIV-transduced cells. The in vivo imaging platform described here can potentially serve as a powerful tool to visualize lentiviral infection, including when and where viraemia rebounds, and how reservoirs are formed and maintained during latency or suppressive ART.

Hierarchically ordered supramolecular protein-polymer composites with thermoresponsive properties

Synthetic macromolecules that can bind and co-assemble with proteins are important for the future development of biohybrid materials. Active systems are further required to create materials that can respond and change their behavior in response to external stimuli. Here we report that stimuli-responsive linear-branched diblock copolymers consisting of a cationic multivalent dendron with a linear thermoresponsive polymer tail at the focal point, can bind and complex Pyrococcus furiosus ferritin protein cages into crystalline arrays. The multivalent dendron structure utilizes cationic spermine units to bind electrostatically on the surface of the negatively charged ferritin cage and the in situ polymerized poly(di(ethylene glycol) methyl ether methacrylate) linear block enables control with temperature. Cloud point of the final product was determined with dynamic light scattering (DLS), and it was shown to be approximately 31 °C at a concentration of 150 mg/L. Complexation of the polymer binder and apoferritin was studied with DLS, small-angle X-ray scattering, and transmission electron microscopy, which showed the presence of crystalline arrays of ferritin cages with a face-centered cubic (fcc, Fm3m)) Bravais lattice where lattice parameter a=18.6 nm. The complexation process was not temperature dependent but the final complexes had thermoresponsive characteristics with negative thermal expansion.

MR imaging techniques for nano-pathophysiology and theranostics

The advent of nanoparticle DDSs (drug delivery systems, nano-DDSs) is opening new pathways to understanding physiology and pathophysiology at the nanometer scale. A nano-DDS can be used to deliver higher local concentrations of drugs to a target region and magnify therapeutic effects. However, interstitial cells or fibrosis in intractable tumors, as occurs in pancreatic or scirrhous stomach cancer, tend to impede nanoparticle delivery. Thus, it is critical to optimize the type and size of nanoparticles to reach the target. High-resolution 3D imaging provides a means of "seeing" the nanoparticle distribution and therapeutic effects. We introduce the concept of "nano-pathophysiological imaging" as a strategy for theranostics. The strategy consists of selecting an appropriate nano-DDS and rapidly evaluating drug effects in vivo to guide the next round of therapy. In this article we classify nano-DDSs by component carrier materials and present an overview of the significance of nano-pathophysiological MRI.

A smart platform for hyperthermia application in cancer treatment: cobalt-doped ferrite nanoparticles mineralized in human ferritin cages

Magnetic nanoparticles, MNPs, mineralized within a human ferritin protein cage, HFt, can represent an appealing platform to realize smart therapeutic agents for cancer treatment by drug delivery and magnetic fluid hyperthermia, MFH. However, the constraint imposed by the inner diameter of the protein shell (ca. 8 nm) prevents its use as heat mediator in MFH when the MNPs comprise pure iron oxide. In this contribution, we demonstrate how this limitation can be overcome through the controlled doping of the core with small amount of Co(II). Highly monodisperse doped iron oxide NPs with average size of 7 nm are mineralized inside a genetically modified variant of HFt, carrying several copies of α-melanocyte-stimulating hormone peptide, which has already been demonstrated to have excellent targeting properties toward melanoma cells. HFt is also conjugated to poly(ethylene glycol) molecules to increase its in vivo stability. The investigation of hyperthermic properties of HFt-NPs shows that a Co doping of 5% is enough to strongly enhance the magnetic anisotropy and thus the hyperthermic efficiency with respect to the undoped sample. In vitro tests performed on B16 melanoma cell line demonstrate a strong reduction of the cell viability after treatment with Co doped HFt-NPs and exposure to the alternating magnetic field. Clear indications of an advanced stage of apoptotic process is also observed from immunocytochemistry analysis. The obtained data suggest this system represents a promising candidate for the development of a protein-based theranostic nanoplatform.

Why and how we determine nephron number

The total number of glomeruli (nephrons) in a kidney is an important microanatomical parameter for at least three reasons: it provides an index of the success/extent of nephrogenesis and can thereby provide insights into the roles of specific genes and feto-maternal environmental factors in nephrogenesis; low nephron number has been linked to an increased risk of cardiovascular and renal disease in adulthood; and knowledge of quantitative kidney microanatomy can illuminate our understanding of physiological mechanisms in health and disease. A range of methods has been used to count glomeruli in kidneys over the past 100 years, with design-based stereology (the physical disector/fractionator combination) considered the gold standard. However, this approach is labor-intensive and expensive, and therefore is not utilized by most laboratories. A new method for counting and sizing every glomerulus in the kidney has recently been described. This method involves in vivo labeling of glomeruli with cationic ferritin, and then magnetic resonance imaging (MRI) of the ex vivo kidney. Values are obtained in one sixth of the time of disector-based approaches. This new MRI method holds great promise for studies of glomerular number and size ex vivo and in vivo.

Pharmacokinetics, pharmacodynamics and physiologically-based pharmacokinetic modelling of monoclonal antibodies

Development of monoclonal antibodies (mAbs) and their functional derivatives represents a growing segment of the development pipeline in the pharmaceutical industry. More than 25 mAbs and derivatives have been approved for a variety of therapeutic applications. In addition, around 500 mAbs and derivatives are currently in different stages of development. mAbs are considered to be large molecule therapeutics (in general, they are 2-3 orders of magnitude larger than small chemical molecule therapeutics), but they are not just big chemicals. These compounds demonstrate much more complex pharmacokinetic and pharmacodynamic behaviour than small molecules. Because of their large size and relatively poor membrane permeability and instability in the conditions of the gastrointestinal tract, parenteral administration is the most usual route of administration. The rate and extent of mAb distribution is very slow and depends on extravasation in tissue, distribution within the particular tissue, and degradation. Elimination primarily happens via catabolism to peptides and amino acids. Although not definitive, work has been published to define the human tissues mainly involved in the elimination of mAbs, and it seems that many cells throughout the body are involved. mAbs can be targeted against many soluble or membrane-bound targets, thus these compounds may act by a variety of mechanisms to achieve their pharmacological effect. mAbs targeting soluble antigen generally exhibit linear elimination, whereas those targeting membrane-bound antigen often exhibit non-linear elimination, mainly due to target-mediated drug disposition (TMDD). The high-affinity interaction of mAbs and their derivatives with the pharmacological target can often result in non-linear pharmacokinetics. Because of species differences (particularly due to differences in target affinity and abundance) in the pharmacokinetics and pharmacodynamics of mAbs, pharmacokinetic/pharmacodynamic modelling of mAbs has been used routinely to expedite the development of mAbs and their derivatives and has been utilized to help in the selection of appropriate dose regimens. Although modelling approaches have helped to explain variability in both pharmacokinetic and pharmacodynamic properties of these drugs, there is a clear need for more complex models to improve understanding of pharmacokinetic processes and pharmacodynamic interactions of mAbs with the immune system. There are different approaches applied to physiologically based pharmacokinetic (PBPK) modelling of mAbs and important differences between the models developed. Some key additional features that need to be accounted for in PBPK models of mAbs are neonatal Fc receptor (FcRn; an important salvage mechanism for antibodies) binding, TMDD and lymph flow. Several models have been described incorporating some or all of these features and the use of PBPK models are expected to expand over the next few years.

The emerging role of MRI in quantitative renal glomerular morphology

Techniques to measure morphological parameters, such as glomerular (and thereby nephron) number, glomerular size, and kidney volume, have been vital to understanding factors contributing to chronic kidney disease (CKD). These techniques have also been important to understanding the associations between CKD and other systemic and cardiovascular diseases and have led to the identification of developmental risk factors for these pathologies. However, existing techniques in quantitative kidney morphology are resource- and time-consuming and are destructive to the organ. This review discusses the emerging generation of techniques to study kidney morphology quantitatively using magnetic resonance imaging (MRI) using the intravenous injection of the superparamagnetic nanoparticle cationic ferritin, which binds to the glomerular basement membrane. A primary advantage of MRI over previously established techniques is the ability to quantify morphology in the intact organ with minimal sample preparation. We highlight areas of research where MRI-based morphological measurements will be helpful in animal models and possibly diagnostic clinical nephrology, discuss technical challenges in light of the progress in MRI techniques to date, and identify novel measurements that may be possible using MRI, both ex vivo and in vivo.

Metalloprotein-based MRI probes

Metalloproteins have long been recognized as key determinants of endogenous contrast in magnetic resonance imaging (MRI) of biological subjects. More recently, both natural and engineered metalloproteins have been harnessed as biotechnological tools to probe gene expression, enzyme activity, and analyte concentrations by MRI. Metalloprotein MRI probes are paramagnetic and function by analogous mechanisms to conventional gadolinium or iron oxide-based MRI contrast agents. Compared with synthetic agents, metalloproteins typically offer worse sensitivity, but the possibilities of using protein engineering and targeted gene expression approaches in conjunction with metalloprotein contrast agents are powerful and sometimes definitive strengths. This review summarizes theoretical and practical aspects of metalloprotein-based contrast agents, and discusses progress in the exploitation of these proteins for molecular imaging applications.

Ferritins for Chemistry and for Life

Ferritins, highly symmetrical protein nanocages, are reactors for Fe2+ and dioxygen or hydrogen peroxide that are found in all kingdoms of life and in many different cells of multicellular organisms. They synthesize iron concentrates required for cells to make cofactors of iron proteins (heme, FeS, mono and diiron). The caged ferritin biominerals, Fe2O3•H2O are also antioxidants, acting as sinks for iron and oxidants scavenged from damaged proteins; genetic regulation of ferritin biosynthesis is sensitive to both iron and oxidants. Here, the emphasis here is ferritin oxidoreductase chemistry, ferritin ion channels for Fe 2+ transit into and out of the protein cage and Fe 3+ O mineral nucleation, and uses of ferritin cages in nanocatalysis and nanomaterial synthesis. The Fe2+ and O ferritin protein reactors, likely critical in the transition from anaerobic to aerobic life on earth, play central, contemporary roles that balance iron and oxygen chemistry in biology and have emerging roles in nanotechnology.

Gadolinium-induced fibrosis testing by protein targeting assay and superparamagnetic iron oxide nanoparticle-based magnetic resonance microscopy of skin and kidneys

Gadolinium-based magnetic resonance imaging (MRI) contrast agents cause undefined fibrosis in kidneys and skin damage. Magnetic resonance microimaging of rat skin and kidney was used first time to identify the physical factors modulating the gadolinium Omniscan®-induced fibrosis by protein targeting. A 500-MHz MR imaging was done to visualize fibrosis in gadolinium-treated animals. Cationic superparamagnetic iron oxide magnetoferritin (SPIOM) was injected in rat to target basement membrane (in rat kidney and different skin structures including epidermis glycolipids and dermis proteins. After MR imaging, excised rat skin and kidneys tissues were imaged by ex vivo 900 MHz MR microimaging to confirm renal fibrosis and skin epidermis thickening. The proton density-weighted images visualized micro details of skin structures and nephron territories while T2-weighted images showed better contrast of tissue structures in both skin and kidney. The gadolinium further enhanced the image contrast and targeted the proteins in renal basement membrane and viable proteins in epidermis. SPIOM enhanced the tissue contrast due to dephasing effect caused by SPIOM on structural changes in nephron and epidermis. Conclusion: Tissue membrane protein and chelate ligand group binding with gadolinium biophysical interaction at molecular level may develop fibrosis. SPIOM injection improved the dephased image contrast of different structures in both skin and nephrons. The epidermis thickening and nephrofibrosis changes may be associated with nephrogenic systemic fibrosis or fibrosing dermatopathy.

Potential of magnetic nanoparticles for targeted drug delivery

Nanoparticles (NPs) play an important role in the molecular diagnosis, treatment, and monitoring of therapeutic outcomes in various diseases. Their nanoscale size, large surface area, unique capabilities, and negligible side effects make NPs highly effective for biomedical applications such as cancer therapy, thrombolysis, and molecular imaging. In particular, nontoxic superparamagnetic magnetic NPs (MNPs) with functionalized surface coatings can conjugate chemotherapeutic drugs or be used to target ligands/proteins, making them useful for drug delivery, targeted therapy, magnetic resonance imaging, transfection, and cell/protein/DNA separation. To optimize the therapeutic efficacy of MNPs for a specific application, three issues must be addressed. First, the efficacy of magnetic targeting/guidance is dependent on particle magnetization, which can be controlled by adjusting the reaction conditions during synthesis. Second, the tendency of MNPs to aggregate limits their therapeutic use in vivo; surface modifications to produce high positive or negative charges can reduce this tendency. Finally, the surface of MNPs can be coated with drugs which can be rapidly released after injection, resulting in targeting of low doses of the drug. Drugs therefore need to be conjugated to MNPs such that their release is delayed and their thermal stability enhanced. This chapter describes the creation of nanocarriers with a high drug-loading capacity comprised of a high-magnetization MNP core and a shell of aqueous, stable, conducting polyaniline derivatives and their applications in cancer therapy. It further summarizes some newly developed methods to synthesize and modify the surfaces of MNPs and their biomedical applications.

Iron transport in cancer cell culture suspensions measured by cell magnetophoresis

Cell motion in a magnetic field reveals the presence of intracellular paramagnetic elements, such as iron or manganese. Under controlled field and liquid media composition, such motion previously allowed us to compare the paramagnetic contribution to cell magnetic susceptibility in erythrocytes differing in the spin state of heme associated with hemoglobin. The method is now tested on cells with less obvious paramagnetic properties: cell cultures derived from human cancers to determine if the magnetophoretic mobility (MM) measurement is sufficiently sensitive to the dysregulation of the intracellular iron metabolism as suggested by reports on loss of iron homeostasis in cancer. The cell lines included hepatocellular carcinoma (Hep 3B 2.1-7 and Hep G2), promyelocytic (HL-60) and chronic myelogenous (K-562) leukemias, histiocytic lymphoma (U-937), tongue (CAL 27) and pharyngeal (Detroit 562) carcinomas, and epitheloid carcinoma (HeLa), whose MM was measured in complete media with standard and elevated soluble iron (ferric nitrate and ferric ammonium citrate), against oxy- and met-hemoglobin erythrocytes used as controls. Different cell lines responded differently to the magnetic field and the soluble iron concentrations in culture media establishing the possibility of single cell elemental analysis by magnetophoresis and magnetic cell separation based upon differences in intracellular iron concentration.

Principles and emerging applications of nanomagnetic materials in medicine

The development of nanometer-scale magnetic materials for biomedical applications spans the interface between the physical sciences and biology. Applications of these materials are rapidly becoming important in medicine and enable targeted therapies and diagnostics. At the same time, specific applications add focus to the development of novel magnetic materials and facilitate a deeper understanding of the physical mechanisms behind their function. This review presents a broad, nontechnical overview of the basis of magnetism in materials at the nanometer scale and describes how these materials are created, characterized, and used. Specific emerging applications in medical diagnostics and therapies are discussed, including cancer cell targeting for thermal ablation, tissue engineering, and three-dimensional noninvasive molecular imaging. Challenges in these fields are discussed, including the toxicity and delivery of magnetic nanomaterials and the sensitivity of imaging and therapeutic techniques. The development of novel nanomagnetic nanomaterials should continue to accelerate as new applications are identified and researchers uncover new mechanisms to increase and modulate magnetism at the nanometer scale.

Preparation of amyloid-like fibrils containing magnetic iron oxide nanoparticles: effect of protein aggregation on proton relaxivity

A method to prepare amyloid-like fibrils functionalized with magnetic nanoparticles has been developed. The amyloid-like fibrils are prepared in a two step procedure, where insulin and magnetic nanoparticles are mixed simply by grinding in the solid state, resulting in a water soluble hybrid material. When the hybrid material is heated in aqueous acid, the insulin/nanoparticle hybrid material self assembles to form amyloid-like fibrils incorporating the magnetic nanoparticles. This results in magnetically labeled amyloid-like fibrils which has been characterized by Transmission Electron Microscopy (TEM) and electron tomography. The influence of the aggregation process on proton relaxivity is investigated. The prepared materials have potential uses in a range of bio-imaging applications.

Synthesis and characterization of potential iron-platinum drugs and supplements by laser liquid photolysis

Highly crystalline nanospherical iron-platinum systems were produced by 248 nm laser irradiation of a liquid precursor at different laser fluences, ranging from 100-375 mJ/cm(2). The influence of laser intensity on particle size, iron composition, and structure was systematically investigated. Different nanostructures of iron-platinum alloy and chemically disordered iron-platinum L10 phase were obtained without annealing. The prepared precursor solution underwent deep photolysis to polycrystalline iron-platinum nanoalloys through Fe(III) acetylacetonate and Pt(II) acetylacetonate. Fe(II) and Pt(I) acetylacetone decomposed into Fe(0) and Pt(0) nanoparticles. We found that the (001) diffraction peak shifted linearly to a lower angle, with the last peak shifting in opposition to the others. This caused the face-centered cubic L10 structure to change its composition according to laser fluence. The nanostructures were shown to contain iron and platinum only by energy-dispersive spectroscopy at several spots. The response of these iron-platinum nanoparticles to infrared depends on their stoichiometric composition, which is controlled by laser fluence.

Simplified synthesis and relaxometry of magnetoferritin for magnetic resonance imaging

Magnetoferritin nanoparticles have been developed as high-relaxivity, functional contrast agents for MRI. Several previous techniques have relied on unloading native ferritin and re-incorporation of iron into the core, often resulting in a polydisperse sample. Here, a simplified technique is developed using commercially available horse spleen apoferritin to create monodisperse magnetoferritin. Iron oxide atoms were incorporated into the protein core via a step-wise Fe(II)Chloride addition to the protein solution under low O(2) conditions; subsequent filtration steps allow for separation of completely filled and superparamagnetic magnetoferritin from the partially filled ferritin. This method yields a monodisperse and homogenous solution of spherical particles with magnetic properties that can be used for molecular magnetic resonance imaging. With a transverse per-iron and per-particle relaxivity of 78 mM(-1) sec(-1) and 404,045 mM(-1) sec(-1), respectively, it is possible to detect ∼ 10 nM nanoparticle concentrations in vivo.

Evaluation of the specificity and sensitivity of ferritin as an MRI reporter gene in the mouse brain using lentiviral and adeno-associated viral vectors

The development of in vivo imaging protocols to reliably track transplanted cells or to report on gene expression is critical for treatment monitoring in (pre)clinical cell and gene therapy protocols. Therefore, we evaluated the potential of lentiviral vectors (LVs) and adeno-associated viral vectors (AAVs) to express the magnetic resonance imaging (MRI) reporter gene ferritin in the rodent brain. First, we compared the induction of background MRI contrast for both vector systems in immune-deficient and immune-competent mice. LV injection resulted in hypointense (that is, dark) changes of T(2)/T(2)(*) (spin-spin relaxation time)-weighted MRI contrast at the injection site, which can be partially explained by an inflammatory response against the vector injection. In contrast to LVs, AAV injection resulted in reduced background contrast. Moreover, AAV-mediated ferritin overexpression resulted in significantly enhanced contrast to background on T(2)(*)-weighted MRI. Although sensitivity associated with the ferritin reporter remains modest, AAVs seem to be the most promising vector system for in vivo MRI reporter gene imaging.