Disruptive chemical doping in a ferritin-based iron oxide nanoparticle to decrease r2 and enhance detection with T1-weighted MRI

Tungsten-based Nanomaterials in the Biomedical Field: A Bibliometric Analysis of Research Progress and Prospects

Tungsten-based nanomaterials (TNMs) with diverse nanostructures and unique physicochemical properties have been widely applied in the biomedical field. Although various reviews have described the application of TNMs in specific biomedical fields, there are still no comprehensive studies that summarize and analyze research trends of the field as a whole. To identify and further promote the development of biomedical TNMs, a bibliometric analysis method is used to analyze all relevant literature on this topic. First, general bibliometric distributions of the dataset by year, country, institute, referenced source, and research hotspots are recognized. Next, a comprehensive review of the subjectively recognized research hotspots in various biomedical fields, including biological sensing, anticancer treatments, antibacterials, and toxicity evaluation, is provided. Finally, the prospects and challenges of TNMs are discussed to provide a new perspective for further promoting their development in biomedical research.

Application of nanomaterials in diagnosis and treatment of glioblastoma

Diagnosing and treating glioblastoma patients is currently hindered by several obstacles, such as tumor heterogeneity, the blood-brain barrier, tumor complexity, drug efflux pumps, and tumor immune escape mechanisms. Combining multiple methods can increase benefits against these challenges. For example, nanomaterials can improve the curative effect of glioblastoma treatments, and the synergistic combination of different drugs can markedly reduce their side effects. In this review, we discuss the progression and main issues regarding glioblastoma diagnosis and treatment, the classification of nanomaterials, and the delivery mechanisms of nanomedicines. We also examine tumor targeting and promising nano-diagnosis or treatment principles based on nanomedicine. We also summarize the progress made on the advanced application of combined nanomaterial-based diagnosis and treatment tools and discuss their clinical prospects. This review aims to provide a better understanding of nano-drug combinations, nano-diagnosis, and treatment options for glioblastoma, as well as insights for developing new tools.

Single-nanometer iron oxide nanoparticles as tissue-permeable MRI contrast agents

Magnetic nanoparticles are robust contrast agents for MRI and often produce particularly strong signal changes per particle. Leveraging these effects to probe cellular- and molecular-level phenomena in tissue can, however, be hindered by the large sizes of typical nanoparticle contrast agents. To address this limitation, we introduce single-nanometer iron oxide (SNIO) particles that exhibit superparamagnetic properties in conjunction with hydrodynamic diameters comparable to small, highly diffusible imaging agents. These particles efficiently brighten the signal in T ₁-weighted MRI, producing per-molecule longitudinal relaxation enhancements over 10 times greater than conventional gadolinium-based contrast agents. We show that SNIOs permeate biological tissue effectively following injection into brain parenchyma or cerebrospinal fluid. We also demonstrate that SNIOs readily enter the brain following ultrasound-induced blood-brain barrier disruption, emulating the performance of a gadolinium agent and providing a basis for future biomedical applications. These results thus demonstrate a platform for MRI probe development that combines advantages of small-molecule imaging agents with the potency of nanoscale materials.

Image analysis techniques to map pyramids, pyramid structure, glomerular distribution, and pathology in the intact human kidney from 3-D MRI

Kidney pathologies are often highly heterogeneous. To comprehensively understand kidney structure and pathology, it is critical to develop tools to map tissue microstructure in the context of the whole, intact organ. Magnetic resonance imaging (MRI) can provide a unique, three-dimensional view of the kidney and allows for measurements of multiple pathological features. Here, we developed a platform to systematically render and map gross and microstructural features of the human kidney based on three-dimensional MRI. These features include pyramid number and morphology as well as the associated medulla and cortex. In a subset of these kidneys, we also mapped individual glomeruli and glomerular volumes using cationic ferritin-enhanced MRI to report intrarenal heterogeneity in glomerular density and size. Finally, we rendered and measured regions of nephron loss due to pathology and individual glomerular volumes in each pyramidal unit. This work provides new tools to comprehensively evaluate the kidney across scales, with potential applications in anatomic and physiological research, transplant allograft evaluation, biomarker development, biopsy guidance, and therapeutic monitoring. These image rendering and analysis tools could eventually impact the field of transplantation medicine to improve longevity matching of donor allografts and recipients and reduce discard rates through the direct assessment of donor kidneys.NEW & NOTEWORTHY We report the application of cutting-edge image analysis approaches to characterize the pyramidal geometry, glomerular microstructure, and heterogeneity of the whole human kidney imaged using MRI. This work establishes a framework to improve the detection of microstructural pathology to potentially facilitate disease monitoring or transplant evaluation in the individual kidney.

Nephron number and its determinants: a 2020 update

Studies of human nephron number have been conducted for well over a century and have uncovered a large variability in nephron number. However, the mechanisms influencing nephron endowment and loss, along with the etiology for the wide range among individuals are largely unknown. Advances in imaging technology have allowed investigators to revisit the principles of renal structure and physiology and their roles in the progression of kidney disease. Here, we will review the latest data on the influences impacting nephron number, innovations made over the last 6 years to understand and integrate renal structure and function, and new developments in the tools used to count nephrons in vivo.

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.

Mapping nephron mass in vivo using positron emission tomography

Nephron number varies widely in humans. A low nephron endowment at birth or a loss of functioning nephrons is strongly linked to increased susceptibility to chronic kidney disease. In this work, we developed a contrast agent, radiolabeled cationic ferritin (RadioCF), to map functioning glomeruli in vivo in the kidney using positron emission tomography (PET). PET radiotracers can be detected in trace doses (<30 nmol), making them useful for rapid clinical translation. RadioCF is formed from cationic ferritin (CF) and with a radioisotope, Cu-64, incorporated into the ferritin core. We showed that RadioCF binds specifically to kidney glomeruli after intravenous injection in mice, whereas radiolabeled noncationic ferritin (RadioNF) and free Cu-64 do not. We then showed that RadioCF-PET can distinguish kidneys in healthy wild-type (WT) mice from kidneys in mice with oligosyndactylism (Os/+), a model of congenital hypoplasia and low nephron mass. The average standardized uptake value (SUV) measured by PET 90 min after injection was 21% higher in WT mice than in Os/+ mice, consistent with the higher glomerular density in WT mice. The difference in peak SUV from SUV at 90 min correlated with glomerular density in male mice from both WT and Os/+ cohorts (R2 = 0.98). Finally, we used RadioCF-PET to map functioning glomeruli in a donated human kidney. SUV within the kidney correlated with glomerular number (R2= 0.78) measured by CF-enhanced magnetic resonance imaging in the same locations. This work suggests that RadioCF-PET appears to accurately detect nephron mass and has the potential for clinical translation.

In-vivo techniques for determining nephron number

PURPOSE OF REVIEW

Many studies have suggested low nephron endowment at birth contributes to the risk of developing hypertension and chronic kidney disease (CKD) later in life. Loss of nephrons with age and disease is largely a subclinical process. New technologies are needed to count nephrons as glomerular filtration rate (GFR) is a poor surrogate for nephron number.

RECENT FINDINGS

Cortical volume, glomerular density, and percent globally sclerotic glomeruli are imperfect surrogates for nephron number. The disector-fractionator method is the most accurate method to count nephrons but is limited to autopsy settings. Glomerular density combined with kidney imaging and ultrafiltration coefficient-based methods require a kidney biopsy, and have been applied in living humans (kidney donors). Low nephron number predicts a higher postdonation urine albumin. Contrast-enhanced MRI has detected glomeruli without a biopsy, but so far, not in living humans.

SUMMARY

Currently, there is no accurate and well tolerated method for determining nephron number in living humans. A clinically useful method may allow GFR to be replaced by its more relevant determinants: nephron number and single nephron GFR. This could revolutionize nephrology by separating the measurement of chronic disease (nephron loss) from more reversible hemodynamic effects (nephron hyperfiltration/hypofiltration).

In vivo measurements of kidney glomerular number and size in healthy and Os/+ mice using MRI

The development of chronic kidney disease (CKD) is associated with the loss of functional nephrons. However, there are no methods to directly measure nephron number in living subjects. Thus, there are no methods to track the early stages of progressive CKD before changes in total renal function. In this work, we used cationic ferritin-enhanced magnetic resonance imaging (CFE-MRI) to enable measurements of glomerular number (N_glom) and apparent glomerular volume (aV_glom) in vivo in healthy wild-type (WT) mice (n = 4) and mice with oligosyndactylism (Os^/+; n = 4), a model of congenital renal hypoplasia leading to nephron reduction. We validated in vivo measurements of N_glom and aV_glom by high-resolution ex vivo MRI. CFE-MRI measured a mean N_glom of 12,220 ± 2,028 and 6,848 ± 1,676 (means ± SD) for WT and Os^/+ mouse kidneys in vivo, respectively. N_glom measured in all mice in vivo using CFE-MRI varied by an average 15% from N_glom measured ex vivo in the same kidney (α = 0.05, P = 0.67). To confirm that CFE-MRI can also be used to track nephron endowment longitudinally, a WT mouse was imaged three times by CFE-MRI over 2 wk. Values of N_glom measured in vivo in the same kidney varied within ~3%. Values of aV_glom calculated from CFE-MRI in vivo were significantly different (~15% on average, P < 0.01) from those measured ex vivo, warranting further investigation. This is the first report of direct measurements of N_glom and aV_glom in healthy and diseased mice in vivo.

High-resolution MRI of kidney microstructures at 7.05 T with an endo-colonic Wireless Amplified NMR detector

To map the hemodynamic responses of kidney microstructures at 7.05 T with improved sensitivity, a Wireless Amplified NMR Detector (WAND) with cylindrical symmetry was fabricated as an endoluminal detector that can convert externally provided wireless signal at 600.71 MHz into amplified MR signals at 300.33 MHz. When this detector was inserted inside colonic lumens to sensitively observe adjacent kidneys, it could clearly identify kidney microstructures in the renal cortex and renal medullary. Owing to the higher achievable spatial resolution, differential hemodynamic responses of kidney microstructures under different breathing conditions could be individually quantified to estimate the underlying correlation between oxygen bearing capability and local levels of oxygen unsaturation. The WAND's ability to map Blood Oxygen Level Dependent (BOLD) signal responses in heterogeneous microstructures will pave way for early-stage diagnosis of kidney diseases, without the use of contrast agents for reduced tissue retention and toxicity.

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.

Nanoparticle-based diagnostic and therapeutic systems for brain tumors

Many theranostic nanoparticles have been tailored for high-efficiency diagnostic or therapeutic agents or applied as carriers and might provide new possibilities for brain tumor diagnosis and treatment.

Measuring rat kidney glomerular number and size in vivo with MRI

number is highly variable in humans and is thought to play an important role in renal health. Chronic kidney disease (CKD) is the result of too few nephrons to maintain homeostasis. Currently, nephron number can only be determined invasively or as a terminal assessment. Due to a lack of tools to measure and track nephron number in the living, the early stages of CKD often go unrecognized, preventing early intervention that might halt the progression of CKD. In this work, we present a technique to directly measure glomerular number ( Nglom) and volume in vivo in the rat kidney ( n = 8) using MRI enhanced with the novel contrast agent cationized ferritin (CFE-MRI). Adult male rats were administered intravenous cationized ferritin (CF) and imaged in vivo with MRI. Glomerular number was measured and each glomerulus was spatially mapped in 3D in the image. Mean apparent glomerular volume (a Vglom) and intrarenal distribution of the individual glomerular volume (IGV), were also measured. These metrics were compared between images of the same kidneys scanned in vivo and ex vivo with CFE-MRI. In vivo Nglom and a Vglom correlated to ex vivo metrics within the same kidneys and were within 10% of Nglom and a Vglom previously validated by stereologic methods. This is the first report of direct in vivo measurements of Nglom and a Vglom, introducing an opportunity to investigate mechanisms of renal disease progression and therapeutic response over time.

Magnetic resonance imaging quantification and biodistribution of magnetic nanoparticles using T1-enhanced contrast

Magnetic iron oxide nanoparticles have been used for various applications such as in the treatment of iron deficiency, as theranostic agents, and as drug carriers. The effective delivery of magnetic iron oxide nanoparticles into the lesion and iron quantification are vital for in vivo theranostic application. To determine the feasibility of using T₁ contrast to non-invasively quantify and monitor the IONPs in vivo, monodispersed Gd-doped iron oxide nanoparticles (GdIONPs) with 4 nm core size were fabricated and were used as T₁-weighted contrast agents to quantify iron contents based on MRI longitudinal relaxation times (T₁). Signal enhancement in positive T₁ contrast caused by GdIONPs was observed in this work. The in vivo T₁ relaxivity of GdIONPs in a tumor matched well with both in vitro T₁ relaxivity and ICP-MS results, demonstrating that the concentration of iron at the tumor site can be directly read from real-time in vivo MRI T₁ relaxivity. Hence, by using this strategy, the Fe content in the lesion can be accurately monitored based on MRI longitudinal relaxation times, and this may shed light on effective magnetic hyperthermia cancer therapy in future.

Exceedingly small iron oxide nanoparticles as positive MRI contrast agents

Medical imaging is routine in the diagnosis and staging of a wide range of medical conditions. In particular, magnetic resonance imaging (MRI) is critical for visualizing soft tissue and organs, with over 60 million MRI procedures performed each year worldwide. About one-third of these procedures are contrast-enhanced MRI, and gadolinium-based contrast agents (GBCAs) are the mainstream MRI contrast agents used in the clinic. GBCAs have shown efficacy and are safe to use with most patients; however, some GBCAs have a small risk of adverse effects, including nephrogenic systemic fibrosis (NSF), the untreatable condition recently linked to gadolinium (Gd) exposure during MRI with contrast. In addition, Gd deposition in the human brain has been reported following contrast, and this is now under investigation by the US Food and Drug Administration (FDA). To address a perceived need for a Gd-free contrast agent with pharmacokinetic and imaging properties comparable to GBCAs, we have designed and developed zwitterion-coated exceedingly small superparamagnetic iron oxide nanoparticles (ZES-SPIONs) consisting of ∼3-nm inorganic cores and ∼1-nm ultrathin hydrophilic shell. These ZES-SPIONs are free of Gd and show a high T₁ contrast power. We demonstrate the potential of ZES-SPIONs in preclinical MRI and magnetic resonance angiography.

MRI tools for assessment of microstructure and nephron function of the kidney

MRI can provide excellent detail of renal structure and function. Recently, novel MR contrast mechanisms and imaging tools have been developed to evaluate microscopic kidney structures including the tubules and glomeruli. Quantitative MRI can assess local tubular function and is able to determine the concentrating mechanism of the kidney noninvasively in real time. Measuring single nephron function is now a near possibility. In parallel to advancing imaging techniques for kidney microstructure is a need to carefully understand the relationship between the local source of MRI contrast and the underlying physiological change. The development of these imaging markers can impact the accurate diagnosis and treatment of kidney disease. This study reviews the novel tools to examine kidney microstructure and local function and demonstrates the application of these methods in renal pathophysiology.

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.

Phenotyping by magnetic resonance imaging nondestructively measures glomerular number and volume distribution in mice with and without nephron reduction

Reduced nephron mass is strongly linked to susceptibility to chronic renal and cardiovascular diseases. There are currently no tools to identify nephropenia in clinical or preclinical diagnostics. Such new methods could uncover novel mechanisms and therapies for chronic kidney disease (CKD) and reveal how variation among traits can affect renal function and morphology. Here we used cationized ferritin (CF)–enhanced MRI (CFE-MRI) to investigate the relationship between glomerular number (Nglom) and volume (Vglom) in kidneys of healthy wild-type mice and mice with oligosyndactylism (Os/+), a model of congenital nephron reduction. Mice were injected with CF and perfused, and the resected kidneys were imaged with 7T MRI to detect CF-labeled glomeruli. CFE-MRI was used to measure the intrarenal distribution of individual glomerular volumes and revealed two major populations of glomeruli distinguished by size. Spatial mapping revealed that the largest glomeruli were located in the juxtamedullary region in both wild-type and Os/+ mice and the smallest population located in the cortex. Os/+ mice had about a 50% reduction and 35% increase of Nglom and Vglom, respectively, in both glomerular populations compared with wild type, consistent with glomerular hypertrophy in the Os/+ mice. Thus, we provide a foundation for whole-kidney, MRI-based phenotyping of mouse renal glomerular morphology and provide new potential for quantitative human renal diagnostics.

Vascular Accessibility of Endothelial Targeted Ferritin Nanoparticles

Targeting nanocarriers to the endothelium, using affinity ligands to cell adhesion molecules such as ICAM-1 and PECAM-1, holds promise to improve the pharmacotherapy of many disease conditions. This approach capitalizes on the observation that antibody-targeted carriers of 100 nm and above accumulate in the pulmonary vasculature more effectively than free antibodies. Targeting of prospective nanocarriers in the 10-50 nm range, however, has not been studied. To address this intriguing issue, we conjugated monoclonal antibodies (Ab) to ICAM-1 and PECAM-1 or their single chain antigen-binding fragments (scFv) to ferritin nanoparticles (FNPs, size 12 nm), thereby producing Ab/FNPs and scFv/FNPs. Targeted FNPs retained their typical symmetric core-shell structure with sizes of 20-25 nm and ∼4-5 Ab (or ∼7-9 scFv) per particle. Ab/FNPs and scFv/FNPs, but not control IgG/FNPs, bound specifically to cells expressing target molecules and accumulated in the lungs after intravenous injection, with pulmonary targeting an order of magnitude higher than free Ab. Most intriguing, the targeting of Ab/FNPs to ICAM-1, but not PECAM-1, surpassed that of larger Ab/carriers targeted by the same ligand. These results indicate that (i) FNPs may provide a platform for targeting endothelial adhesion molecules with carriers in the 20 nm size range, which has not been previously reported; and (ii) ICAM-1 and PECAM-1 (known to localize in different domains of endothelial plasmalemma) differ in their accessibility to circulating objects of this size, common for blood components and nanocarriers.

Use of Cationized Ferritin Nanoparticles to Measure Renal Glomerular Microstructure with MRI

Magnetic resonance imaging (MRI) is becoming important for whole-kidney assessment of glomerular morphology, both in vivo and ex vivo. MRI-based renal morphological measurements can be made in intact organs and allow direct measurements of every perfused glomerulus. Cationic ferritin (CF) is used as a superparamagnetic contrast agent for MRI. CF binds to the glomerular basement membrane after intravenous injection, allowing direct, whole-kidney measurements of glomerular number, volume, and volume distribution. Here we describe the production, testing, and use of CF as an MRI contrast agent for quantitative glomerular morphology in intact mouse, rat, and human kidneys.

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.

MRI-based glomerular morphology and pathology in whole human kidneys

Nephron number (N(glom)) and size (V(glom)) are correlated with risk for chronic cardiovascular and kidney disease and may be predictive of renal allograft viability. Unfortunately, there are no techniques to assess N(glom) and V(glom) in intact kidneys. This work demonstrates the use of cationized ferritin (CF) as a magnetic resonance imaging (MRI) contrast agent to measure N(glom) and V(glom) in viable human kidneys donated to science. The kidneys were obtained from patients with varying levels of cardiovascular and renal disease. CF was intravenously injected into three viable human kidneys. A fourth control kidney was perfused with saline. After fixation, immunofluorescence and electron microscopy confirmed binding of CF to the glomerulus. The intact kidneys were imaged with three-dimensional MRI and CF-labeled glomeruli appeared as punctate spots. Custom software identified, counted, and measured the apparent volumes of CF-labeled glomeruli, with an ~6% false positive rate. These measurements were comparable to stereological estimates. The MRI-based technique yielded a novel whole kidney distribution of glomerular volumes. Histopathology demonstrated that the distribution of CF-labeled glomeruli may be predictive of glomerular and vascular disease. Variations in CF distribution were quantified using image texture analyses, which be a useful marker of glomerular sclerosis. This is the first report of direct measurement of glomerular number and volume in intact human kidneys.