Mechanism of cellular uptake and impact of ferucarbotran on macrophage physiology

CT imaging of and therapy for inflammatory bowel disease via low molecular weight dextran coated ceria nanoparticles

Inflammatory bowel disease (IBD) affects approximately 3.1 million individuals in the U.S., causing deleterious symptoms such as bloody diarrhea and leading to an increased risk of colorectal cancer. Effective imaging is crucial for diagnosing and managing IBD, as it allows for accurate assessment of disease severity, guides treatment decisions, and monitors therapeutic responses. Computed tomography (CT) with contrast agents is the gold standard for imaging the gastrointestinal tract (GIT). However, current agents are less effective in obese patients and lack specificity for inflamed regions associated with IBD. Moreover, IBD treatments often have limited efficacy and do not address the role of oxidative stress in IBD progression. This study explores dextran-coated cerium oxide nanoparticles (Dex-CeNP) as a CT contrast agent and therapeutic for IBD, leveraging cerium's superior K-edge energy profile, dextran's inflammation-specific targeting, and cerium oxide's antioxidant properties. Herein, we synthesized Dex-CeNP formulations using 5, 10, 25, and 40 kDa dextran to explore the effect of dextran coating molecular weight. In vitro assays showed formulation biocompatibility and demonstrated that 5 kDa Dex-CeNP had the highest catalytic activity, which translated into improved suppression of inflammation. As a result, this formulation was selected for in vivo use. In vivo CT imaging of mice subjected to dextran sodium sulfate (DSS) colitis showed that Dex-CeNP provided better contrast in the GIT of mice with colitis compared to iopamidol (ISO), with pronounced attenuation in the large intestine and disease- specific retention at 24 h. Additionally, Dex-CeNP significantly decreased Disease Activity Index (DAI) scores, and diminished gastrointestinal bleeding when compared with a currently approved drug, indicating that it is an effective treatment for colitis. Studies also revealed that the Dex-CeNPs were safe and well-excreted following administration. In summary, Dex-CeNP has significant promise as a dual-purpose agent for CT imaging and treatment of IBD.

The Effect of the Size of Gold Nanoparticle Contrast Agents on CT Imaging of the Gastrointestinal Tract and Inflammatory Bowel Disease

Ulcerative colitis (UC) is a chronic inflammatory bowel disease (IBD). CT imaging with contrast agents is commonly used for visualizing the gastrointestinal (GI) tract in UC patients. Contrast agents that provide enhanced imaging performance are highly valuable in this field. Recent studies have made significant progress in developing better contrast agents for imaging the gastrointestinal tract using nanoparticles. However, the impact of nanoparticle size on this application remains unexplored. Gold nanoparticles (AuNPs) serve as an ideal model to investigate the effect of nanoparticle size on imaging of the gastrointestinal tract due to their controllable synthesis across a broad size range. In this study, we synthesized AuNPs with core sizes ranging from 5 to 75 nm to examine the effect of the size in this setting. AuNPs were coated with poly(ethylene glycol) (PEG) to enhance stability and biocompatibility. In vitro tests show that gold nanoparticles are cytocompatible with macrophage cells (∼100% cell viability) and remain stable under acidic conditions, with no significant size changes over time. Phantom imaging studies using a clinical CT scanner indicated that there was no effect of nanoparticle size on CT contrast production, as previously demonstrated. In vivo imaging using a mouse model of acute colitis revealed a strong contrast generation throughout the GI tract for all agents tested. For the most part, in vivo contrast was independent of AuNP size, although AuNP outperformed iopamidol (a clinically approved control agent). In addition, differences in attenuation trends were observed between healthy and colitis mice. We also observed almost complete clearance at 24 h of all formulations tested (less than 0.7% ID/g was retained), supporting their value as a model platform for studying nanoparticle behavior in imaging. In conclusion, this study highlights the potential of nanoparticles as effective contrast agents for CT imaging of the gastrointestinal tract (GIT) in the UC. Further systemic research is needed to explore contrast agents that can specifically image disease processes in this disease setting.

In vitro assessments of nanoplexes of polyethylenimine-coated graphene oxide-plasmid through various cancer cell lines and primary mesenchymal stem cells

Efficient gene therapy relies on an efficient gene delivery system. Viral gene delivery approaches excel in transferring and expressing external genes; however, their immunogenicity and difficulty in large-scale production limit their clinical applications. In contrast, nanoparticle-based gene delivery systems have gained increasing attention due to less immunogenicity and more convenience for large-scale production. Nevertheless, their poor transfection efficiency compared to viral systems remains a significant obstacle. In the present study, we investigated the transfection efficiency of our PEI-coated graphene oxides in HEK293T, Calu-3, Calu-6 cell lines, and primary human bone marrow mesenchymal stem cell (MSC). The high surface ratio and good biocompatibility of graphene oxide make it an appealing tool for gene delivery systems. However, the low dispersity of graphene oxide in aqueous environments is the first barrier that needs to be conquered. For this, we enhanced the dispersity and stability of graphene oxide in water by sonicating it for at least 5 hours at a pH of 7. Then, graphene oxide was conjugated with branched PEI (25 kDa) to have a positive charge, enabling it to condense nucleic acids with a naturally negative potential. The physio-chemical characteristics of our synthesized nano-carriers (GO-PEI) were determined by DLS, FT-IR, and AFM. The utilized plasmid in polyplexes contained a GFP gene, allowing us to verify transfection efficiency through fluorescent microscopy and flow cytometry. While GO-PEI carriers were highly efficient in transfecting HEK293T cells, the transfection efficiency in MSCs and Calu-3 cells was notably low. We suppose that the main reason for the low transfection efficiency of GO-PEI in these cells is due to its higher toxicity. Despite this, considering the various advantages of graphene oxide in drug delivery as well as its optical and electrical applications in biomedicine, we propose to functionalize graphene oxide with more biocompatible materials to enhance its potential as a successful gene carrier in these cell types.

Diagnostic and therapeutic roles of iron oxide nanoparticles in biomedicine

Nanotechnology changed our understanding of physics and chemics and influenced the biomedical field. Iron oxide nanoparticles (IONs) are one of the first emerging biomedical applications of nanotechnology. The IONs are composed of iron oxide core exhibiting magnetism and coated with biocompatible molecules. The small size, strong magnetism, and biocompatibility of IONs facilitate the application of IONs in the medical imaging field. We listed several clinical available IONs including Resovist (Bayer Schering Pharma, Berlin, Germany) and Feridex intravenous (I.V.)/Endorem as magnetic resonance (MR) contrast agents for liver tumor detection. We also illustrated GastroMARK as a gastrointestinal contrast agent for MR imaging. Recently, IONs named Feraheme for treating iron-deficiency anemia have been approved by the Food and Drug Administration. Moreover, tumor ablation by IONs named NanoTherm has also been discussed. In addition to the clinical application, several potential biomedical applications of IONs including cancer-targeting capability by conjugating IONs with cancer-specific ligands, cell trafficking tools, or tumor ablation agents have also been discussed. With the growing awareness of nanotechnology, further application of IONs is still on the horizon that would shed light on biomedicine.

Superparamagnetic Iron Oxide Nanoparticles: Cytotoxicity, Metabolism, and Cellular Behavior in Biomedicine Applications

Superparamagnetic iron oxide nanoparticles (SPIONs) have been widely investigated and applied in the field of biomedicine due to their excellent superparamagnetic properties and reliable traceability. However, with the optimization of core composition, shell types and transfection agents, the cytotoxicity and metabolism of different SPIONs have great differences, and the labeled cells also show different cellular behaviors. Therefore, a holistic review of the construction and application of SPIONs is desired. This review focuses the advances of SPIONs in the field of biomedicine in recent years. After summarizing the toxicity of different SPIONs, the uptake, distribution and metabolism of SPIONs in vitro were discussed. Then, the regulation of labeled-cells behavior is outlined. Furthermore, the major challenges in the optimization process of SPIONs and insights on its future developments are proposed.

Personalised Profiling of Innate Immune Memory Induced by Nano-Imaging Particles in Human Monocytes

Engineered nanoparticles used for medical purposes must meet stringent safety criteria, which include immunosafety, i.e., the inability to activate possibly detrimental immune/inflammatory effects. Even medical nanomaterials devoid of direct immunotoxic or inflammatory effects may have an impact on human health if able to modify innate memory, which is the ability to “prime” future immune responses towards a different, possibly more detrimental reactivity. Although innate memory is usually protective, anomalous innate memory responses may be at the basis of immune pathologies. In this study, we have examined the ability of two nanomaterials commonly used for diagnostic imaging purposes, gold and iron oxide nanoparticles, to induce or modulate innate memory, using an in vitro model based on human primary monocytes. Monocytes were exposed in culture to nanoparticles alone or together with the bacterial agent LPS (priming phase/primary response), then rested for six days (extinction phase), and eventually challenged with LPS (memory/secondary response). The memory response to the LPS challenge was measured as changes in the production of inflammatory (TNFα, IL-6) and anti-inflammatory cytokines (IL-10, IL-1Ra), as compared to unprimed monocytes. The results show that both types of nanoparticles can have an effect in the induction of memory, with changes observed in the cytokine production. By comparing nanomaterials of different shapes (spherical vs. rod-shaped gold particles) and different size (17 vs. 22 nm diameter spherical iron oxide particles), it was evident that innate memory could be differentially induced and modulated depending on size, shape and chemical composition. However, the main finding was that the innate memory effect of the particles was strongly donor-dependent, with monocytes from each donor showing a distinct memory profile upon priming with the same particles, thereby making impossible to draw general conclusions on the particle effects. Thus, in order to predict the effect of imaging nanoparticles on the innate memory of patients, a personalised profiling would be required, able to take in consideration the peculiarities of the individual innate immune reactivity.

Iron Oxide Nanoparticles in Bioimaging - An Immune Perspective

Iron oxide nanoparticles (IONPs) bear big hopes in nanomedicine due to their (potential) applications in tumor therapy, drug delivery or bioimaging. However, as foreign entities, such particles may be recognized by the immune system and, thus, lead to inflammation, hypersensitivity or anaphylactic shock. In addition, an overload with iron is known to cause oxidative stress. In this short review, we summarize the biological effects of such particles with a major focus on IONP-formulations used for bioimaging purposes and their effects on the human immune system. We conclude that especially the characteristics of the particles (size, shape, surface charge, coating, etc.) as well as the presence of bystander substances, such as bacterial endotoxin are important factors determining the resulting biological and immunological effects of IONPs. Further studies are needed in order to establish clear structure-activity relationships.

Tracking adoptive T cell immunotherapy using magnetic particle imaging

Adoptive cellular therapy (ACT) is a potent strategy to boost the immune response against cancer. ACT is effective against blood cancers but faces challenges in treating solid tumors. A critical step for the success of ACT immunotherapy is to achieve efficient trafficking and persistence of T cells to solid tumors. Non-invasive tracking of the accumulation of adoptively transferred T cells to tumors would greatly accelerate development of more effective ACT strategies. We demonstrate the use of magnetic particle imaging (MPI) to non-invasively track ACT T cells in vivo in a mouse model of brain cancer. Magnetic labeling did not impair primary tumor-specific T cells in vitro, and MPI allowed the detection of labeled T cells in the brain after intravenous or intracerebroventricular administration. These results support the use of MPI to track adoptively transferred T cells and accelerate the development of ACT treatments for brain tumors and other cancers.

Effects of Ipriflavone-Loaded Mesoporous Nanospheres on the Differentiation of Endothelial Progenitor Cells and Their Modulation by Macrophages

Angiogenic biomaterials are designed to promote vascularization and tissue regeneration. Nanoparticles of bioactive materials loaded with drugs represent an interesting strategy to stimulate osteogenesis and angiogenesis and to inhibit bone resorption. In this work, porcine endothelial progenitor cells (EPCs), essential for blood vessel formation, were isolated and characterized to evaluate the in vitro effects of unloaded (NanoMBGs) and ipriflavone-loaded nanospheres (NanoMBG-IPs), which were designed to prevent osteoporosis. The expression of vascular endothelial growth factor receptor 2 (VEGFR2) was studied in EPCs under different culture conditions: (a) treatment with NanoMBGs or NanoMBG-IPs, (b) culture with media from basal, M1, and M2 macrophages previously treated with NanoMBGs or NanoMBG-IPs, (c) coculture with macrophages in the presence of NanoMBGs or NanoMBG-IPs, and (d) coculture with M2d angiogenic macrophages. The endocytic mechanisms for nanosphere incorporation by EPCs were identified using six different endocytosis inhibitors. The results evidence the great potential of these nanomaterials to enhance VEGFR2 expression and angiogenesis, after intracellular incorporation by EPCs through clathrin-dependent endocytosis, phagocytosis, and caveolae-mediated uptake. The treatment of EPCs with basal, M1, and M2 macrophage culture media and EPC/macrophage coculture studies also confirmed the angiogenic effect of these nanospheres on EPCs, even in the presence of phagocytic cells.

Ex vivo magnetic particle imaging of vascular inflammation in abdominal aortic aneurysm in a murine model

Abdominal aortic aneurysms (AAAs) are currently one of the leading causes of death in developed countries. Inflammation is crucial in the disease progression, having a substantial impact on various determinants in AAAs development. Magnetic particle imaging (MPI) is an innovative imaging modality, enabling the highly sensitive detection of magnetic nanoparticles (MNPs), suitable as surrogate marker for molecular targeting of vascular inflammation. For this study, Apolipoprotein E-deficient-mice underwent surgical implantation of osmotic minipumps with constant Angiotensin II infusion. After 3 and 4 weeks respectively, in-vivo-magnetic resonance imaging (MRI), ex-vivo-MPI and ex-vivo-magnetic particle spectroscopy (MPS) were performed. The results were validated by histological analysis, immunohistology and laser ablation-inductively coupled plasma-mass spectrometry. MR-angiography enabled the visualization of aneurysmal development and dilatation in the experimental group. A close correlation (R = 0.87) with histological area assessment was measured. Ex-vivo-MPS revealed abundant iron deposits in AAA samples and ex-vivo histopathology measurements were in good agreement (R = 0.76). Ex-vivo-MPI and MPS results correlated greatly (R = 0.99). CD68-immunohistology stain and Perls’-Prussian-Blue-stain confirmed the colocalization of macrophages and MNPs. This study demonstrates the feasibility of ex-vivo-MPI for detecting inflammation in AAA. The quantitative ability for mapping MNPs establishes MPI as a promising tool for monitoring inflammatory progression in AAA in an experimental setting.

Cytoprotective effects of antioxidant supplementation on mesenchymal stem cell therapy

Mesenchymal stem cells (MSCs) are earmarked as perfect candidates for cell therapy and tissue engineering due to their capacity to differentiate into different cell types. However, their potential for application in regenerative medicine declines when the levels of the reactive oxygen and nitrogen species (RONS) increase from the physiological levels, a phenomenon which is at least inevitable in ex vivo cultures and air-exposed damaged tissues. Increased levels of RONS can alter the patterns of osteogenic and adipogenic differentiation and inhibit proliferation, as well. Besides, oxidative stress enhances senescence and cell death, thus lowering the success rates of the MSC engraftment. Hence, in this review, we have selected some representatives of antioxidants and newly emerged nano antioxidants in three main categories, including chemical compounds, biometabolites, and protein precursors/proteins, which are proved to be effective in the treatment of MSCs. We will focus on how antioxidants can be applied to optimize the clinical usage of the MSCs and their associated signaling pathways. We have also reviewed several paralleled properties of some antioxidants and nano antioxidants which can be simultaneously used in real-time imaging, scaffolding techniques, and other applications in addition to their primary antioxidative function.

Mechanisms for cellular uptake of nanosized clinical MRI contrast agents

Engineered Nanomaterials (NMs), such as Superparamagnetic Iron Oxide Nanoparticles (SPIONs), offer significant benefits in a wide range of applications, including cancer diagnostic and therapeutic strategies. However, the use of NMs in biomedicine raises safety concerns due to lack of knowledge on possible biological interactions and effects. The initial basis for using SPIONs as biomedical MRI contrast enhancement agents was the idea that they are selectively taken up by macrophage cells, and not by the surrounding cancer cells. To investigate this claim, we analyzed the uptake of SPIONs into well-established cancer cell models and benchmarked this against a common macrophage cell model. In combination with fluorescent labeling of compartments and siRNA silencing of various proteins involved in common endocytic pathways, the mechanisms of internalization of SPIONs in these cell types has been ascertained utilizing reflectance confocal microscopy. Caveolar mediated endocytosis and macropinocytosis are both implicated in SPION uptake into cancer cells, whereas in macrophage cells, a clathrin-dependant route appears to predominate. Colocalization studies confirmed the eventual fate of SPIONs as accumulation in the degradative lysosomes. Dissolution of the SPIONs within the lysosomal environment has also been determined, allowing a fuller understanding of the cellular interactions, uptake, trafficking and effects of SPIONs within a variety of cancer cells and macrophages. Overall, the behavior of SPIONS in non-phagocytotic cell lines is broadly similar to that in the specialist macrophage cells, although some differences in the uptake patterns are apparent.

D-mannose-Coating of Maghemite Nanoparticles Improved Labeling of Neural Stem Cells and Allowed Their Visualization by ex vivo MRI after Transplantation in the Mouse Brain

Magnetic resonance imaging (MRI) of superparamagnetic iron oxide-labeled cells can be used as a non-invasive technique to track stem cells after transplantation. The aim of this study was to (1) evaluate labeling efficiency of D-mannose-coated maghemite nanoparticles (D-mannose(γ-Fe2O3)) in neural stem cells (NSCs) in comparison to the uncoated nanoparticles, (2) assess nanoparticle utilization as MRI contrast agent to visualize NSCs transplanted into the mouse brain, and (3) test nanoparticle biocompatibility. D-mannose(γ-Fe2O3) labeled the NSCs better than the uncoated nanoparticles. The labeled cells were visualized by ex vivo MRI and their localization subsequently confirmed on histological sections. Although the progenitor properties and differentiation of the NSCs were not affected by labeling, subtle effects on stem cells could be detected depending on dose increase, including changes in cell proliferation, viability, and neurosphere diameter. D-mannose coating of maghemite nanoparticles improved NSC labeling and allowed for NSC tracking by ex vivo MRI in the mouse brain, but further analysis of the eventual side effects might be necessary before translation to the clinic.

Missing-in-metastasis protein promotes internalization of magnetic nanoparticles via association with clathrin light chain and Rab7

BACKGROUND

Magnetic nanoparticles (MNPs) have been widely used in biomedical applications. Proper control of the duration of MNPs in circulation promises to improve further their applications, in particularly drug delivery. It is known that the uptake of tissue-associated MNPs is mainly carried out by macrophages. Yet, the molecular mechanism to control MNPs internalization in macrophages remains to be elusive. Missing-in-metastasis (MIM) is a scaffolding protein that is highly expressed in macrophages and regulates receptor-mediated endocytosis. We hypothesize that uptake of MNPs may also involve the function of MIM.

METHODS

We investigated the effect of MIM expression on the intracellular trafficking of MNPs by transmission electronic microscopy, flow cytometry, o-phenanthroline photometric analysis, Perl's staining, immunofluorescence microscopy and co-immunoprecipitation. To explore the molecular events in MIM-mediated MNPs uptake, we examined the effect of MNPs on the interaction of MIM with clathrin, Rab5 and Rab7.

RESULTS

Uptake of MNPs was significantly enhanced in cells overexpressing MIM. Upon exposure to MNPs, MIM was associated with clathrin light chain in endocytic vesicles and Rab7, a protein that regulates late endosomes. However, MNPs caused dissociation of MIM with Rab5, an early endosome-associated protein.

CONCLUSIONS

MIM regulates internalization of MNPs via promoting their trafficking from plasma membrane to late endosomes.

GENERAL SIGNIFICANCE

Our data unveiled a novel pathway which MNPs internalization and intracellular trafficking in macrophages. This new pathway may allow us to control the uptake of MNPs within cells by targeting MIM, thereby improving their medical applications.

Magnetic cell delivery for the regeneration of musculoskeletal and neural tissues

Magnetic targeting is a cell delivery system using the magnetic labeling of cells and the magnetic field; it has been developed for minimally invasive cell transplantation. Cell transplantation with both minimal invasiveness and high efficacy on tissue repair can be achieved by this system. Magnetic targeting has been applied for the transplantation of bone marrow mesenchymal stem cells, blood CD133-positive cells, neural progenitor cells, and induced pluripotent stem cells, and for the regeneration of bone, cartilage, skeletal muscles, and the spinal cord. It enhances the accumulation and adhesion of locally injected cells, resulting in the improvement of tissue regeneration. It is a promising technique for minimally invasive and effective cell transplantation therapy.

The Immunoimaging Toolbox

The recent clinical success of cancer immunotherapy has renewed interest in the development of tools to image the immune system. In general, immunotherapies attempt to enable the body's own immune cells to seek out and destroy malignant disease. Molecular imaging of the cells and molecules that regulate immunity could provide unique insight into the mechanisms of action, and failure, of immunotherapies. In this article, we will provide a comprehensive overview of the current state-of-the-art immunoimaging toolbox with a focus on imaging strategies and their applications toward immunotherapy.

Immunological effects of iron oxide nanoparticles and iron-based complex drug formulations: Therapeutic benefits, toxicity, mechanistic insights, and translational considerations

Nanotechnology offers several advantages for drug delivery. However, there is the need for addressing potential safety concerns regarding the adverse health effects of these unique materials. Some such effects may occur due to undesirable interactions between nanoparticles and the immune system, and they may include hypersensitivity reactions, immunosuppression, and immunostimulation. While strategies, models, and approaches for studying the immunological safety of various engineered nanoparticles, including metal oxides, have been covered in the current literature, little attention has been given to the interactions between iron oxide-based nanomaterials and various components of the immune system. Here we provide a comprehensive review of studies investigating the effects of iron oxides and iron-based nanoparticles on various types of immune cells, highlight current gaps in the understanding of the structure-activity relationships of these materials, and propose a framework for capturing their immunotoxicity to streamline comparative studies between various types of iron-based formulations.

Fucoidan Prolongs the Circulation Time of Dextran-Coated Iron Oxide Nanoparticles

The magnetic properties and safety of dextran-coated superparamagnetic iron oxide nanoparticles (SPIONs) have facilitated their clinical use as MRI contrast agents and stimulated research on applications for SPIONs in particle imaging and magnetic hyperthermia. The wider clinical potential of SPIONs, however, has been limited by their rapid removal from circulation via the reticuloendothelial system (RES). We explored the possibility of extending SPION circulatory time using fucoidan, a seaweed-derived food supplement, to inhibit RES uptake. The effects of fucoidan on SPION biodistribution were evaluated using ferucarbotran, which in its pharmaceutical formulation (Resovist) targets the RES. Ferucarbotran was radiolabeled at the iron oxide core with technetium-99m (99mTc; t1/2 = 6 h) or zirconium-89 (89Zr; t1/2 = 3.3 days). Results obtained with 99mTc-ferucarbotran demonstrated that administration of fucoidan led to a 4-fold increase in the circulatory half-life (t1/2 slow) from 37.4 to 150 min (n = 4; P < 0.0001). To investigate whether a longer circulatory half-life could lead to concomitant increased tumor uptake, the effects of fucoidan were tested with 89Zr-ferucarbotran in mice bearing syngeneic subcutaneous (GL261) tumors. In this model, the longer circulatory half-life achieved with fucoidan was associated with a doubling in tumor SPION uptake (n = 5; P < 0.001). Fucoidan was also effective in significantly increasing the circulatory half-life of perimag-COOH, a commercially available SPION with a larger hydrodynamic size (130 nm) than ferucarbotran (65 nm). These findings indicate successful diversion of SPIONs away from the hepatic RES and show realistic potential for future clinical applications.

Non-invasive cell tracking of SPIO labeled cells in an intrinsic regenerative environment: The axolotl limb

Non-invasive methods to track the progress of stem cell therapies are important in the development of future regenerative therapies. Super-paramagnetic iron oxide particles (SPIOs) have previously been applied to track cells using magnetic resonance imaging (MRI) in vivo in non-regenerative animal models. To the best of the author's knowledge, the present study investigated for the first time, the feasibility of tracking SPIO labeled cells in an intrinsic regenerative environment, the regenerating limb of the axolotl, and investigated the homing of stem cell-like blastema cells to the regenerative zone. Viability and labeling success of labeled axolotl blastema cells was tested in vitro using cell culture and histology. SPIO labeling was performed in situ by intramuscular injections and mapped using MRI. Enhanced permeability and retention (EPR) effects were evaluated in the blastema, liver, heart, kidney and a back muscle. Finally, SPIO/Fluorophore-labeled blastema cells were injected intravascularly and tracked using MRI and fluorescence imaging. It was demonstrated that SPIO labeling had no effect on axolotl cell viability in vitro. In situ labeling resulted in an MRI signal alteration during 48 days of regeneration. EPR effect of unbound SPIO was observed only in the liver. MRI tracking revealed increased concentrations of SPIO labeled blastema cells in the liver, kidney and heart, however not the blastema of intravascularly injected axolotls. In conclusion, the results demonstrated that SPIO labeling facilitated non-invasive tracking of injected cells in the regenerating axolotl limb. An early homing mechanism of injected blastema cells to an injury site was not observed.

Coating Metal Nanoparticle Surfaces with Small Organic Molecules Can Reduce Nonspecific Cell Uptake

Elucidation of mechanisms of uptake of nanoparticles by cells and methods to prevent this uptake is essential for many applications of nanoparticles. Most recent studies have focused on the role of proteins that coat nanoparticles and have employed PEGylation, particularly dense coatings of PEG, to reduce protein opsonization and cell uptake. Here we show that small molecule coatings on metallic nanoparticles can markedly reduce cell uptake for very sparsely PEGylated nanoparticles. Similar results were obtained in media with and without proteins, suggesting that protein opsonization is not the primary driver of this phenomenon. The reduction in cell uptake is proportional to the degree of surface coverage by the small molecules. Probing cell uptake pathways using inhibitors suggested that the primary role of increased surface coverage is to reduce nanoparticles' interactions with the scavenger receptors. This work highlights an under-investigated mechanism of cell uptake that may have played a role in many other studies and also suggests that a wide variety of molecules can be used alongside PEGylation to stably passivate nanoparticle surfaces for low cell uptake.

Current applications and future prospects of nanomaterials in tumor therapy

Tumors are one of the most serious human diseases and cause numerous global deaths per year. In spite of many strategies applied in tumor therapy, such as radiation therapy, chemotherapy, surgery, and a combination of these treatments, tumors are still the foremost killer worldwide among human diseases, due to their specific limitations, such as multidrug resistance and side effects. Therefore, it is urgent and necessary to develop new strategies for tumor therapy. Recently, the fast development of nanoscience has paved the way for designing new strategies to treat tumors. Nanomaterials have shown great potential in tumor therapy, due to their unique properties, including passive targeting, hyperthermia effects, and tumor-specific inhibition. This review summarizes the recent progress using the innate antitumor properties of metallic and nonmetallic nanomaterials to treat tumors, and related challenges and prospects are discussed.

Biological effects of iron oxide-protamine sulfate complex on mesenchymal stem cells and its relaxometry based labeling optimization for cellular MRI

Mesenchymal stem cells (MSCs) are frequently used as a therapeutic, but reliable imaging technique to longitudinally evaluate the engraftment of transplanted cells is inadequate. For magnetic resonance imaging (MRI), it is essential to understand the technical competence of in vitro stem cells labeling with iron oxide with regard to its relaxation behavior and significance of its biological expressions. The purpose of the study was to optimize the effective labeling of MSCs with high transverse relaxivity iron oxide contrast agent with protamine sulfate and also evaluate the biological effects (phenotype and function) of labeled MSCs. Our results demonstrated that 50:3µg/ml of Fe-Pro complex containing 10% serum at an incubation time of 6h were ideal for effective in vitro labeling. Relaxometry study demonstrated that almost an 8-fold increase in relaxation rate (R₂) was observed in labeled MSCs by comparing with unlabeled. Marginal alteration in Oct4 and CD146 genes, and phenotypic CD45 expressions were detected after labeling. T2-weighted images and histological analysis confirmed the homing of transplanted cells to the site of injury. The relaxometry based optimized labeling method of MSCs could be extrapolated for cellular MRI and may be useful in stem cell tracking in various pre-clinical and clinical studies.

Improved biocompatibility and efficient labeling of neural stem cells with poly(L-lysine)-coated maghemite nanoparticles

BACKGROUND

Cell tracking is a powerful tool to understand cellular migration, dynamics, homing and function of stem cell transplants. Nanoparticles represent possible stem cell tracers, but they differ in cellular uptake and side effects. Their properties can be modified by coating with different biocompatible polymers. To test if a coating polymer, poly(L-lysine), can improve the biocompatibility of nanoparticles applied to neural stem cells, poly(L-lysine)-coated maghemite nanoparticles were prepared and characterized. We evaluated their cellular uptake, the mechanism of internalization, cytotoxicity, viability and proliferation of neural stem cells, and compared them to the commercially available dextran-coated nanomag(®)-D-spio nanoparticles.

RESULTS

Light microscopy of Prussian blue staining revealed a concentration-dependent intracellular uptake of iron oxide in neural stem cells. The methyl thiazolyl tetrazolium assay and the calcein acetoxymethyl ester/propidium iodide assay demonstrated that poly(L-lysine)-coated maghemite nanoparticles scored better than nanomag(®)-D-spio in cell labeling efficiency, viability and proliferation of neural stem cells. Cytochalasine D blocked the cellular uptake of nanoparticles indicating an actin-dependent process, such as macropinocytosis, to be the internalization mechanism for both nanoparticle types. Finally, immunocytochemistry analysis of neural stem cells after treatment with poly(L-lysine)-coated maghemite and nanomag(®)-D-spio nanoparticles showed that they preserve their identity as neural stem cells and their potential to differentiate into all three major neural cell types (neurons, astrocytes and oligodendrocytes).

CONCLUSION

Improved biocompatibility and efficient cell labeling makes poly(L-lysine)-coated maghemite nanoparticles appropriate candidates for future neural stem cell in vivo tracking studies.

Immunotoxicity and genotoxicity testing of PLGA-PEO nanoparticles in human blood cell model

A human blood cell model for immunotoxicity and genotoxicity testing was used to measure the response to polylactic-co-glycolic acid (PLGA-PEO) nanoparticle (NP) (0.12, 3, 15 and 75 μg/cm(2) exposure in fresh peripheral whole blood cultures/isolated peripheral blood mononuclear cell cultures from human volunteers (n = 9-13). PLGA-PEO NPs were not toxic up to dose 3 μg/cm(2); dose of 75 μg/cm(2) displays significant decrease in [(3)H]-thymidine incorporation into DNA of proliferating cells after 4 h (70% of control) and 48 h (84%) exposure to NPs. In non-cytotoxic concentrations, in vitro assessment of the immunotoxic effects displayed moderate but significant suppression of proliferative activity of T-lymphocytes and T-dependent B-cell response in cultures stimulated with PWM > CON A, and no changes in PHA cultures. Decrease in proliferative function was the most significant in T-cells stimulated with CD3 antigen (up to 84%). Cytotoxicity of natural killer cells was suppressed moderately (92%) but significantly in middle-dosed cultures (4 h exposure). On the other hand, in low PLGA-PEO NPs dosed cultures, significant stimulation of phagocytic activity of granulocytes (119%) > monocytes (117%) and respiratory burst of phagocytes (122%) was recorded. Genotoxicity assessment revealed no increase in the number of micronucleated binucleated cells and no induction of SBs or oxidised DNA bases in PLGA-PEO-treated cells. To conclude on immuno- and genotoxicity of PLGA-PEO NPs, more experiments with various particle size, charge and composition need to be done.

Downregulation of MIM protein inhibits the cellular endocytosis process of magnetic nanoparticles in macrophages

MIM plays a positive role in the RAW 264.7 cellular endocytosis process of iron oxide nanoparticles mainly in clathrin-mediated pathway, which is a meaningful molecular basis for biomedical applications of nanomaterials.

Prolonging the circulatory retention of SPIONs using dextran sulfate: in vivo tracking achieved by functionalisation with near-infrared dyes

The rapid reticuloendothelial system (RES) mediated clearance of superparamagnetic iron oxide nanoparticles (SPIONs) from circulation is considered a major limitation of their clinical utility. We aimed to address this by using dextran sulfate 500 (DSO4 500), a Kupffer cell blocking agent, to prolong SPIONs circulatory time. Blood concentrations of SPIONs are difficult to quantify due to the presence of haemoglobin. We therefore developed methods to functionalise SPIONs with near-infrared (NIR) dyes in order to trace their biodistribution. Two SPIONs were investigated: Nanomag®-D-spio-NH(2) and Ferucarbotran. Nanomag®-D-spio-NH(2) was functionalised using NHS (N-hydroxysuccinimide) ester NIR dye and Ferucarbotran was labelled using periodate oxidation followed by reductive amination or a combination of EDC (ethyl(dimethylaminopropyl) carbodiimide )/NHS and click chemistries. Stability after conjugation was confirmed by dynamic light scattering (DLS), superconducting quantum interference device (SQUID) and transmission electron microscopy (TEM). In vivo experiments with the functionalised SPIONs showed a significant improvement in SPIONs blood concentrations in mice pre-treated with dextran sulfate sodium salt 500 (DSO4 500).

Effects of PVA coated nanoparticles on human immune cells

Nanotechnology provides new opportunities in human medicine, mainly for diagnostic and therapeutic purposes. The autoimmune disease rheumatoid arthritis (RA) is often diagnosed after irreversible joint structural damage has occurred. There is an urgent need for a very early diagnosis of RA, which can be achieved by more sensitive imaging methods. Superparamagnetic iron oxide nanoparticles (SPION) are already used in medicine and therefore represent a promising tool for early diagnosis of RA. The focus of our work was to investigate any potentially negative effects resulting from the interactions of newly developed amino-functionalized amino-polyvinyl alcohol coated (a-PVA) SPION (a-PVA-SPION), that are used for imaging, with human immune cells. We analyzed the influence of a-PVA-SPION with regard to cell survival and cell activation in human whole blood in general, and in human monocytes and macrophages representative of professional phagocytes, using flow cytometry, multiplex suspension array, and transmission electron microscopy. We found no effect of a-PVA-SPION on the viability of human immune cells, but cytokine secretion was affected. We further demonstrated that the percentage of viable macrophages increased on exposure to a-PVA-SPION. This effect was even stronger when a-PVA-SPION were added very early in the differentiation process. Additionally, transmission electron microscopy analysis revealed that both monocytes and macrophages are able to endocytose a-PVA-SPION. Our findings demonstrate an interaction between human immune cells and a-PVA-SPION which needs to be taken into account when considering the use of a-PVA-SPION in human medicine.

New findings about iron oxide nanoparticles and their different effects on murine primary brain cells

The physicochemical properties of superparamagnetic iron oxide nanoparticles (SPIOs) enable their application in the diagnostics and therapy of central nervous system diseases. However, since crucial information regarding side effects of particle–cell interactions within the central nervous system is still lacking, we investigated the influence of novel very small iron oxide particles or the clinically approved ferucarbotran or ferumoxytol on the vitality and morphology of brain cells. We exposed primary cell cultures of microglia and hippocampal neurons, as well as neuron–glia cocultures to varying concentrations of SPIOs for 6 and/or 24 hours, respectively. Here, we show that SPIO accumulation by microglia and subsequent morphological alterations strongly depend on the respective nanoparticle type. Microglial viability was severely compromised by high SPIO concentrations, except in the case of ferumoxytol. While ferumoxytol did not cause immediate microglial death, it induced severe morphological alterations and increased degeneration of primary neurons. Additionally, primary neurons clearly degenerated after very small iron oxide particle and ferucarbotran exposure. In neuron–glia cocultures, SPIOs rather stimulated the outgrowth of neuronal processes in a concentration- and particle-dependent manner. We conclude that the influence of SPIOs on brain cells not only depends on the particle type but also on the physiological system they are applied to.

Nanoparticle-based autoimmune disease therapy

The goal of immunotherapy against autoimmunity is to block pathogenic inflammation without impairing immunity against infections and tumours. Regulatory T-cells (Tregs) play a central role in maintaining immune homeostasis, and autoimmune inflammation is frequently associated with decreased numbers and/or function of these T-cells. Therapies harnessing Tregs to treat autoimmune inflammation remain under-developed with caveats ranging from the lack of antigenic and disease specificity to the potential phenotypic and functional instability of in vitro-expanded Treg cells in vivo. Here, we review nanotechnology-based approaches designed to promote immune tolerance through various mechanisms, ranging from systemic or local suppression of antigen-presenting cells and deletion of antigen-specific T-cells, to the systemic expansion of antigen- and disease-specific Treg cells in vivo.

Clearance of depot vaccine SPIO-labeled antigen and substrate visualized using MRI

Immunotherapies, including peptide-based vaccines, are a growing area of cancer research, and understanding their mechanism of action is crucial for their continued development and clinical application. Exploring the biodistribution of vaccine components may be key to understanding this action. This work used magnetic resonance imaging (MRI) to characterize the in vivo biodistribution of the antigen and oil substrate of the vaccine delivery system known as DepoVax(TM). DepoVax uses a novel adjuvanted lipid-in-oil based formulation to solubilise antigens and promote a depot effect. In this study, antigen or oil were tagged with superparamagnetic iron oxide (SPIO), making them visible on MR images. This enables tracking of individual vaccine components to determine changes in biodistribution. Mice were injected with SPIO-labeled antigen or SPIO-labeled oil, and imaged to examine clearance of labeled components from the vaccine site. The SPIO-antigen was steadily cleared, with nearly half cleared within two months post-vaccination. In contrast, the SPIO-oil remained relatively unchanged. The biodistribution of the SPIO-antigen component within the vaccine site was heterogeneous, indicating the presence of active clearance mechanisms, rather than passive diffusion or drainage. Mice injected with SPIO-antigen also showed MRI contrast for several weeks post-vaccination in the draining inguinal lymph node. These results indicate that MRI can visualize the in vivo longitudinal biodistribution of vaccine components. The sustained clearance is consistent with antigen up-take and trafficking by immune cells, leading to accumulation in the draining lymph node, which corresponds to the sustained immune responses and reduced tumor burden observed in vaccinated mice.

Cellular magnetic resonance with iron oxide nanoparticles: long-term persistence of SPIO signal in the CNS after transplanted cell death

AIM

To study the specificity of cellular MRI based on superparamagnetic iron oxide particles (SPIOs), especially within the CNS.

MATERIALS & METHODS

A microglial cell line was engineered for the expression of a suicide gene, the receptor of diphtheria toxin (DT), and two reporter genes, green fluorescent protein and luciferase, in order to induce, in a controlled manner, cell death and test it through bioluminescence. SPIO-labeled DT-sensitive and control DT-insensitive cells were transplanted into the brains of mice, which underwent serial MRI and bioluminescence studies before and up to 90 days after DT-induced cell death.

RESULTS

No variations in SPIO signal voids were detected along longitudinal monitoring in brain hemispheres transplanted with DT-sensitive cells. Ex vivo analyses showed persistence of iron nanoparticle deposits at transplantation sites.

CONCLUSION

Due to the long-term persistence of signal after transplanted cell death, caution is advised when SPIOs are employed for cell tracking.

Molecular imaging of macrophage enzyme activity in cardiac inflammation

Molecular imaging is highly advantageous as various insidious inflammatory events can be imaged in a serial and quantitative fashion. Combined with the conventional imaging modalities like computed tomography (CT), magnetic resonance (MR) and nuclear imaging, it helps us resolve the extent of ongoing pathology, quantify inflammation and predict outcome. Macrophages are increasingly gaining importance as an imaging biomarker in inflammatory cardiovascular diseases. Macrophages, recruited to the site of injury, internalize necrotic or foreign material. Along with phagocytosis, activated macrophages release proteolytic enzymes like matrix metalloproteinases (MMPs) and cathepsins into the extracellular environment. Pro-inflammatory monocytes and macrophages also induce tissue oxidative damage through the inflammatory enzyme myeloperoxidase (MPO). In this review we will highlight recent advances in molecular macrophage imaging. Particular stress will be given to macrophage functional and enzymatic activity imaging which targets phagocytosis, proteolysis and myeloperoxidase activity imaging.

Iron oxide nanoparticles suppress the production of IL-1beta via the secretory lysosomal pathway in murine microglial cells

Background

Superparamagnetic iron oxide nanoparticles (IONPs) have been used as magnetic resonance imaging contrast agents for various research and diagnostic purposes, such as the detection of neuroinflammation and blood-brain-barrier integrity. As the central resident macrophage-like cells, microglia are responsible for managing foreign agents invading the CNS. The present study investigated the direct effect of IONPs on the production of pro-inflammatory cytokines by murine microglia stimulated with lipopolysaccharide (LPS).

Methods

Primary murine microglial cells were pretreated with IONPs (1–50 μg Fe/mL) for 30 min and then stimulated with LPS (100 ng/mL) for 24 h. Confocal microscopy is used to visualize the intracellular IONP distribution and secretory lysosomes after staining with LysoTracker and Rab27a, respectively. The production of interleukin (IL)-1β and tumor necrosis factor (TNF)-α was quantified by ELISA. The activity of IL-1β converting enzyme (ICE) and TNF-α converting enzyme (TACE) was measured by fluorescent microplate assay using specific substrates. The lysosomal number, alkalinity, permeability and cathepsin B activity were determined by flow cytometry with ectodermal dysplasia-1, lysosensor and acridine orange staining, and using cathepsin B specific substrate, respectively.

Results

Confocal imaging revealed that IONPs were markedly engulfed by microglia. Exposure to IONPs attenuated the production of IL-1β, but not TNF-α. Concordantly, the activity of ICE, but not the TACE, was suppressed in IONP-treated cells. Mechanistic studies showed that IONPs accumulated in lysosomes and the number of lysosomes was increased in IONP-treated cells. In addition, exposure to IONPs increased lysosomal permeability and alkalinity, but decreased the activity of cathepsin B, a secretory lysosomal enzyme involved in the activation of ICE.

Conclusions

Our results demonstrated a contrasting effect of IONPs on the production of IL-1β and TNF-α by LPS-stimulated microglia, in which the attenuation of IL-1β by IONPs was mediated by inhibiting the secretory lysosomal pathway of cytokine processing.

Molecular responses of mouse macrophages to copper and copper oxide nanoparticles inferred from proteomic analyses

The molecular responses of macrophages to copper-based nanoparticles have been investigated via a combination of proteomic and biochemical approaches, using the RAW264.7 cell line as a model. Both metallic copper and copper oxide nanoparticles have been tested, with copper ion and zirconium oxide nanoparticles used as controls. Proteomic analysis highlighted changes in proteins implicated in oxidative stress responses (superoxide dismutases and peroxiredoxins), glutathione biosynthesis, the actomyosin cytoskeleton, and mitochondrial proteins (especially oxidative phosphorylation complex subunits). Validation studies employing functional analyses showed that the increases in glutathione biosynthesis and in mitochondrial complexes observed in the proteomic screen were critical to cell survival upon stress with copper-based nanoparticles; pharmacological inhibition of these two pathways enhanced cell vulnerability to copper-based nanoparticles, but not to copper ions. Furthermore, functional analyses using primary macrophages derived from bone marrow showed a decrease in reduced glutathione levels, a decrease in the mitochondrial transmembrane potential, and inhibition of phagocytosis and of lipopolysaccharide-induced nitric oxide production. However, only a fraction of these effects could be obtained with copper ions. In conclusion, this study showed that macrophage functions are significantly altered by copper-based nanoparticles. Also highlighted are the cellular pathways modulated by cells for survival and the exemplified cross-toxicities that can occur between copper-based nanoparticles and pharmacological agents.

Effects of DMSA-coated Fe3O4 nanoparticles on the transcription of genes related to iron and osmosis homeostasis

In this article, we checked the effect of 2,3-dimercaptosuccinic acid-coated Fe(3)O(4) nanoparticles on gene expression of mouse macrophage RAW264.7 cells and found that the transcription of several important genes related to intracellular iron homeostasis were significantly changed. We thus speculated that the cellular iron homeostasis might be disturbed by this nanoparticle through releasing iron ion in cells. To verify this speculation, we first confirmed the transcriptional changes of several key iron homeostasis- related genes, such as Tfrc, Trf, and Lcn2, using quantitative PCR, and found that an iron ion chelator, desferrioxamine, could alleviate the transcriptional alterations of two typical genes, Tfrc and Lcn2. Then, we designed and validated a method based on centrifugation for assaying intracellular irons in ion and nanoparticle state. After extensive measures of intracellular iron in two forms and total iron, we found that the intracellular iron ion significantly increased with intracellular total iron and nanoparticle iron, demonstrating degradation of this nanoparticle into iron ion in cells. We next mimicked the intralysosomal environment in vitro and verified that the internalized iron nanoparticle could release iron ion in lysosome. We found that as another important compensatory response to intracellular overload of iron ion, cells significantly downregulated the expressions of genes belonging to solute carrier family which are responsible for transferring many organic solutes into cells, such as Slc5a3 and Slc44a1, in order to prevent more organic solutes into cells and thus lower the intracellular osmosis. Based on these findings, we profiled a map of gene effects after cells were treated with this iron nanoparticle and concluded that the iron nanoparticles might be more detrimental to cell than iron ion due to its intracellular internalization fashion, nonspecific endocytosis.

Mechanism of cellular uptake of graphene oxide studied by surface-enhanced Raman spectroscopy

The last few years have witnessed rapid development of biological and medical applications of graphene oxide (GO), such as drug/gene delivery, biosensing, and bioimaging. However, little is known about the cellular uptake mechanism and pathway of GO. In this work, surface-enhanced Raman scattering (SERS) spectroscopy is employed to investigate the cellular internalization of GO loaded with Au nanoparticles (NPs) by Ca Ski cells. The presence of Au NPs on the surface of GO enables detection of enhanced intrinsic Raman signals of GO inside the cell. The SERS results reveal that GO is distributed inhomogeneously inside the cell. Furthermore, internalization of Au-GO into Ca Ski cells is mainly via clathrin-mediated endocytosis, and is an energy-dependent process.

Superparamagnetic iron oxide nanoparticles: magnetic nanoplatforms as drug carriers

A targeted drug delivery system is the need of the hour. Guiding magnetic iron oxide nanoparticles with the help of an external magnetic field to its target is the principle behind the development of superparamagnetic iron oxide nanoparticles (SPIONs) as novel drug delivery vehicles. SPIONs are small synthetic γ-Fe₂O₃ (maghemite) or Fe₃O₄ (magnetite) particles with a core ranging between 10 nm and 100 nm in diameter. These magnetic particles are coated with certain biocompatible polymers, such as dextran or polyethylene glycol, which provide chemical handles for the conjugation of therapeutic agents and also improve their blood distribution profile. The current research on SPIONs is opening up wide horizons for their use as diagnostic agents in magnetic resonance imaging as well as for drug delivery vehicles. Delivery of anticancer drugs by coupling with functionalized SPIONs to their targeted site is one of the most pursued areas of research in the development of cancer treatment strategies. SPIONs have also demonstrated their efficiency as nonviral gene vectors that facilitate the introduction of plasmids into the nucleus at rates multifold those of routinely available standard technologies. SPION-induced hyperthermia has also been utilized for localized killing of cancerous cells. Despite their potential biomedical application, alteration in gene expression profiles, disturbance in iron homeostasis, oxidative stress, and altered cellular responses are some SPION-related toxicological aspects which require due consideration. This review provides a comprehensive understanding of SPIONs with regard to their method of preparation, their utility as drug delivery vehicles, and some concerns which need to be resolved before they can be moved from bench top to bedside.