Superparamagnetic MRI probes for in vivo tracking of dendritic cell migration with a clinical 3 T scanner

Helios as a Potential Biomarker in Systemic Lupus Erythematosus and New Therapies Based on Immunosuppressive Cells

The Helios protein (encoded by the IKZF2 gene) is a member of the Ikaros transcription family and it has recently been proposed as a promising biomarker for systemic lupus erythematosus (SLE) disease progression in both mouse models and patients. Helios is beginning to be studied extensively for its influence on the T regulatory (Treg) compartment, both CD4+ Tregs and KIR+/Ly49+ CD8+ Tregs, with alterations to the number and function of these cells correlated to the autoimmune phenomenon. This review analyzes the most recent research on Helios expression in relation to the main immune cell populations and its role in SLE immune homeostasis, specifically focusing on the interaction between T cells and tolerogenic dendritic cells (tolDCs). This information could be potentially useful in the design of new therapies, with a particular focus on transfer therapies using immunosuppressive cells. Finally, we will discuss the possibility of using nanotechnology for magnetic targeting to overcome some of the obstacles related to these therapeutic approaches.

Molecular Imaging of Innate Immunity and Immunotherapy

The innate immune system plays a key role as the first line of defense in various human diseases including cancer, cardiovascular and inflammatory diseases. In contrast to tissue biopsies and blood biopsies, in vivo imaging of the innate immune system can provide whole body measurements of immune cell location and function and changes in response to disease progression and therapy. Rationally developed molecular imaging strategies can be used in evaluating the status and spatio-temporal distributions of the innate immune cells in near real-time, mapping the biodistribution of novel innate immunotherapies, monitoring their efficacy and potential toxicities, and eventually for stratifying patients that are likely to benefit from these immunotherapies. In this review, we will highlight the current state-of-the-art in noninvasive imaging techniques for preclinical imaging of the innate immune system particularly focusing on cell trafficking, biodistribution, as well as pharmacokinetics and dynamics of promising immunotherapies in cancer and other diseases; discuss the unmet needs and current challenges in integrating imaging modalities and immunology and suggest potential solutions to overcome these barriers.

Polyelectrolyte Coating of Ferumoxytol Differentially Impacts the Labeling of Inflammatory and Steady-State Dendritic Cell Subtypes

Engineered magnetic nanoparticles (MNPs) are emerging as advanced tools for medical applications. The coating of MNPs using polyelectrolytes (PEs) is a versatile means to tailor MNP properties and is used to optimize MNP functionality. Dendritic cells (DCs) are critical regulators of adaptive immune responses. Functionally distinct DC subsets exist, either under steady-state or inflammatory conditions, which are explored for the specific treatment of various diseases, such as cancer, autoimmunity, and transplant rejection. Here, the impact of the PE coating of ferumoxytol for uptake into both inflammatory and steady-state DCs and the cellular responses to MNP labeling is addressed. Labeling efficiency by uncoated and PE-coated ferumoxytol is highly variable in different DC subsets, and PE coating significantly improves the labeling of steady-state DCs. Uncoated ferumoxytol results in increased cytotoxicity of steady-state DCs after labeling, which is abolished by the PE coating, while no increased cell death is observed in inflammatory DCs. Furthermore, uncoated and PE-coated ferumoxytol appear immunologically inert in inflammatory DCs, but they induce activation of steady-state DCs. These results show that the PE coating of MNPs can be applied to endow particles with desired properties for enhanced uptake and cell type-specific responses in distinct target DC populations.

Clinical translational barriers against nanoparticle-based imaging agents

Nanoparticle based imaging agents (NIAs) have been intensively explored in bench studies. Unfortunately, only a few cases have made their ways to clinical translation. In this review, clinical trials of NIAs were investigated for understanding possible barriers behind that. First, the complexity of multifunctional NIAs is considered a main barrier because it brings uncertainty to batch-to-batch fabrication, and results in sophisticated in vivo behaviors. Second, inadequate biosafety studies slow down the translational work. Third, NIA uptake at disease sites is highly heterogeneous, and often exhibits poor targeting efficiency. Focusing on the aforementioned problems, key design parameters were analyzed including NIAs' size, composition, surface characteristics, dosage, administration route, toxicity, whole-body distribution and clearance in clinical trials. Possible strategies were suggested to overcome these barriers. Besides, regulatory guidelines as well as scale-up and reproducibility during manufacturing process were covered as they are also key factors to consider during clinical translation of NIAs.

In Vivo MRI Tracking of Tumor Vaccination and Antigen Presentation by Dendritic Cells

Cancer vaccination using tumor antigen-primed dendritic cells (DCs) was introduced in the clinic some 25 years ago, but the overall outcome has not lived up to initial expectations. In addition to the complexity of the immune response, there are many factors that determine the efficacy of DC therapy. These include accurate administration of DCs in the target tissue site without unwanted cell dispersion/backflow, sufficient numbers of tumor antigen-primed DCs homing to lymph nodes (LNs), and proper timing of immunoadjuvant administration. To address these uncertainties, proton (1H) and fluorine (19F) magnetic resonance imaging (MRI) tracking of ex vivo pre-labeled DCs can now be used to non-invasively determine the accuracy of therapeutic DC injection, initial DC dispersion, systemic DC distribution, and DC migration to and within LNs. Magnetovaccination is an alternative approach that tracks in vivo labeled DCs that simultaneously capture tumor antigen and MR contrast agent in situ, enabling an accurate quantification of antigen presentation to T cells in LNs. The ultimate clinical premise of MRI DC tracking would be to use changes in LN MRI signal as an early imaging biomarker to predict the efficacy of tumor vaccination and anti-tumor response long before treatment outcome becomes apparent, which may aid clinicians with interim treatment management.

Recent advances in biomaterial-boosted adoptive cell therapy

Adoptive immunotherapies based on the transfer of functional immune cells hold great promise in treating a wide range of malignant diseases, especially cancers, autoimmune diseases, and infectious diseases. However, manufacturing issues and biological barriers lead to the insufficient population of target-selective effector cells at diseased sites after adoptive transfer, hindering effective clinical translation. The convergence of immunology, cellular biology, and materials science lays a foundation for developing biomaterial-based engineering platforms to overcome these challenges. Biomaterials can be rationally designed to improve ex vivo immune cell expansion, expedite functional engineering, facilitate protective delivery of immune cells in situ, and navigate the infused cells in vivo. Herein, this review presents a comprehensive summary of the latest progress in biomaterial-based strategies to enhance the efficacy of adoptive cell therapy, focusing on function-specific biomaterial design, and also discusses the challenges and prospects of this field.

Iron oxide nanoparticles for immune cell labeling and cancer immunotherapy

Cancer immunotherapy is a novel approach to cancer treatment that leverages components of the immune system as opposed to chemotherapeutics or radiation. Cell migration is an integral process in a therapeutic immune response, and the ability to track and image the migration of immune cells in vivo allows for better characterization of the disease and monitoring of the therapeutic outcomes. Iron oxide nanoparticles (IONPs) are promising candidates for use in immunotherapy as they are biocompatible, have flexible surface chemistry, and display magnetic properties that may be used in contrast-enhanced magnetic resonance imaging (MRI). In this review, advances in application of IONPs in cell tracking and cancer immunotherapy are presented. Following a brief overview of the cancer immunity cycle, developments in labeling and tracking various immune cells using IONPs are highlighted. We also discuss factors that influence the effectiveness of IONPs as MRI contrast agents. Finally, we outline different approaches for cancer immunotherapy and highlight current efforts that utilize IONPs to stimulate immune cells to enhance their activity and response to cancer.

Metabolic Conversion and Removal of Manganese Ferrite Nanoparticles in RAW264.7 Cells and Induced Alteration of Metal Transporter Gene Expression

Background

Manganese Ferrite Nanoparticles (Mn-IONPs) are widely used in biomedical field and their cytotoxicity has been initially explored, but the mechanism remains obscure. The nano-bio interactions are believed to be crucial for cytotoxicity mechanism, while little data have been acquired.

Methods

Mn-IONPs were synthesized by thermal decomposition of acetylacetonate precursor. After physicochemical characterization, we analyzed the metabolic conversion and removal of Mn-IONPs in RAW264.7 cells by Prussian blue staining, TEM, HRTEM and elemental quantitative analysis, followed by gene expression evaluation using quantitative RT-PCR.

Results

Mn-IONPs were successfully synthesized. Both the uptake and cytotoxicity of Mn-IONPs on RAW264.7 cells were time- and dose-dependent. After internalized, Mn-IONPs were passed to daughter cells with passages on. Meanwhile, Mn-IONPs were exocytosed and digested to metal ions and further excreted out, resulted in the labeling rate and ions contents decreased gradually. As ion influx related genes, the expressions of ZIP14, IRP2, FtH and DMT1 were suppressed within 24 hours but overexpressed to a plateau at the 48th hour in a dose-dependent manner. At the 72nd hour, ZIP14 and DMT1 mRNA levels decreased toward normal, while IRP2 and FtH kept up-regulated. As efflux related genes, FPN, SLC30A10 and Hamp2 genes were up-regulated within 24–72 hours; SPCA1 was suppressed at the 24th and 72nd hour, while overexpressed at the 48th hour. All the efflux related genes’ mRNA had a dose-dependent increasing manner at the corresponding time points.

Conclusion

Mn-IONPs showed time- and dose-dependent cytotoxicity and cell labeling rate in RAW264.7 cells. Accompanying with the intracellular catabolic breakdown and exocytosis of Mn-IONPs, RAW264.7 cells also secreted and re-uptook manganese and iron ions to maintain intracellular homeostasis in the succeeding passages. And the metabolic conversion of Mn-IONPs in RAW264.7 cells can affect the expression of ZIP14, DMT1, FPN, SLC30A10, IRP2, FtH, Hamp2 and SPCA1 genes.

The MRI-Visible Nanocomposite Facilitates the Delivery and Tracking of siRNA Loaded DC Vaccine in the Breast Cancer Model

Dendritic cell (DC) vaccines have recently been developed for the treatment of various cancers but often do not function as well as expected, primarily due to the highly complex in vivo immune environment. This proof-of-principle study aimed to test the feasibility of modulating the in vivo behaviors of DC vaccines (DCVs) by introducing siRNA-laden magnetic resonance (MR) imaging nanovectors into cells, while providing visible information on their homing to lymph nodes. The N-alkyl-PEI2k-LAC/SPIO nanocomposites were prepared and characterized, showing favorable properties of siRNA transfection and MRI labeling efficiency in DCs. Cell viability assays revealed no observable effects on the survival and phenotype of DCs if the concentration of the complex was within 8 μg Fe/ml. An orthotopic mouse model of breast cancer was developed. The DCVs transfected with IDO siRNA contained nanocomposites were adoptively transferred to start the treatment. MR imaging clearly visualized the homing of DCVs into lymph nodes. At the end of the treatment, DCVs presented significantly better tumor suppression than DCs or PBS (P < 0.05). Generally, the N-alkyl-PEI2k-LAC/SPIO nanocomposites represent a highly efficient MR imaging platform for siRNA transfection that is potentially useful for in vivo tracking of vaccine cells.

Characterization of activation induced [18]F-FDG uptake in Dendritic Cells

AIM

 Activation of immune cells leads to enhanced glucose uptake that can be visualized by [¹⁸]F-Fluorodeoxyglucose ([¹⁸]F-FDG) positron emission tomography/computed tomography (PET/CT). Dendritic cells (DC) are essential for the function of the adaptive immune system. In contrast to other immune cells metabolic changes leading to an increase of [¹⁸]F-FDG uptake are poorly investigated. Here, we analysed the impact of different DC activation pathways on their [¹⁸]F-FDG uptake. This effect was then used to radiolabel DC with [¹⁸]F-FDG and track their migration in vivo.

METHODS

 DC were generated from bone marrow progenitors (BMDC) or isolated from spleens (SPDC) of C57BL/6 mice. After stimulation with the TLR ligands LPS and CpG or anti-CD40 antibody for up to 72 hours activation markers and glucose transporters (GLUTs) were measured by flow cytometry. Uptake of [¹⁸]F-FDG was measured by gamma-counting. DC lysates were analysed for expression of glycolysis relevant proteins by mass spectrometry (MS). [¹⁸]F-FDG-labeled DC were injected into footpads of mice to image DC migration.

RESULTS

 BMDC and SPDC showed strong upregulation of activation markers predominantly 24 hours after TLR stimulation followed by higher uptake of [¹⁸]F-FDG. In line with this, the expression of GLUTs was upregulated during the course of activation. Furthermore, MS analyses of DC lysates revealed differential regulation of glycolysis relevant proteins according to the stimulatory pathway. As a proof of principle, DC were labeled with [¹⁸]F-FDG upon activation to follow their migration in vivo via PET/MRI.

CONCLUSION

 Immune stimulation of DC leads to enhanced [¹⁸]F-FDG uptake into DC, representing the typical shift to aerobic glycolysis in immune cells after activation.

Improving Tumor Retention of Effector Cells in Adoptive Cell Transfer Therapies by Magnetic Targeting

Adoptive cell transfer therapy is a promising anti-tumor immunotherapy in which effector immune cells are transferred to patients to treat tumors. However, one of its main limitations is the inefficient trafficking of inoculated effector cells to the tumor site and the small percentage of effector cells that remain activated when reaching the tumor. Multiple strategies have been attempted to improve the entry of effector cells into the tumor environment, often based on tumor types. It would be, however, interesting to develop a more general approach, to improve and facilitate the migration of specific activated effector lymphoid cells to any tumor type. We and others have recently demonstrated the potential for adoptive cell transfer therapy of the combined use of magnetic nanoparticle-loaded lymphoid effector cells together with the application of an external magnetic field to promote the accumulation and retention of lymphoid cells in specific body locations. The aim of this review is to summarize and highlight the recent findings in the field of magnetic accumulation and retention of effector cells in tumors after adoptive transfer, and to discuss the possibility of using this approach for tumor targeting with chimeric antigen receptor (CAR) T-cells.

In vivo Imaging Technologies to Monitor the Immune System

The past two decades have brought impressive advancements in immune modulation, particularly with the advent of both cancer immunotherapy and biologic therapeutics for inflammatory conditions. However, the dynamic nature of the immune response often complicates the assessment of therapeutic outcomes. Innovative imaging technologies are designed to bridge this gap and allow non-invasive visualization of immune cell presence and/or function in real time. A variety of anatomical and molecular imaging modalities have been applied for this purpose, with each option providing specific advantages and drawbacks. Anatomical methods including magnetic resonance imaging (MRI), computed tomography (CT), and ultrasound provide sharp tissue resolution, which can be further enhanced with contrast agents, including super paramagnetic ions (for MRI) or nanobubbles (for ultrasound). Conjugation of the contrast material to an antibody allows for specific targeting of a cell population or protein of interest. Protein platforms including antibodies, cytokines, and receptor ligands are also popular choices as molecular imaging agents for positron emission tomography (PET), single-photon emission computerized tomography (SPECT), scintigraphy, and optical imaging. These tracers are tagged with either a radioisotope or fluorescent molecule for detection of the target. During the design process for immune-monitoring imaging tracers, it is important to consider any potential downstream physiologic impact. Antibodies may deplete the target cell population, trigger or inhibit receptor signaling, or neutralize the normal function(s) of soluble proteins. Alternatively, the use of cytokines or other ligands as tracers may stimulate their respective signaling pathways, even in low concentrations. As in vivo immune imaging is still in its infancy, this review aims to describe the modalities and immunologic targets that have thus far been explored, with the goal of promoting and guiding the future development and application of novel imaging technologies.

Gadolinium-doped Au@prussian blue nanoparticles as MR/SERS bimodal agents for dendritic cell activating and tracking

In vivo tracking of dendritic cell (DC) migration to the lymphatic system is essential for evaluating the outcome of DC-based immunotherapies. Novel multimodal imaging strategies with high analytical performance are urgently needed to supply complementary information about the migration and colonization of DCs. In this study, we designed a bimodal imaging agent, namely Au@Prussian blue-Gd@ovalbumin nanoparticles (APG@OVA NPs), for activating DCs and real-time tracking of DC migration process by magnetic resonance imaging (MRI). Moreover, the distribution of the colonized DCs in the lymphatic system was profiled at the single-cell levels based on surface-enhanced Raman scattering (SERS) technique.

Methods: In this strategy, PBs as cyanide (CN)-bridged coordination blocks were assembled onto the gold nanoparticles core to provide SERS signal in the Raman-silent region (1800 and 2800 cm^-1), which could avoid background signal interference. The doping Gd³⁺ located in the lattice of PB enables the MRI ability with high relaxivity of the probe. Ovalbumin, an egg allergen, was used as an antigen to activate DCs due to its immunological properties. The prepared APG@OVA NP agents were used to activate DCs with high efficacy and to track their migration and distribution in vivo through SERS/MR bimodal imaging.

Results: The APG@OVA NP agents could not only enable DC activating and labeling, but also achieve real-time monitoring of DC migration in vivo and accurate profiling of DC distribution in the lymphatic system. MR imaging indicated the time-dependent migration of the APG@OVA NP-labeled DCs from the footpad to the sentinel lymph node. The background-free Raman mapping of the lymph node tissue slice demonstrated that the activated DCs have successfully colonized to the sentinel lymph node.

Conclusion: Concerning the high activating efficacy, dual complementary imaging readouts, and low biological toxicity, the APG@OVA NPs act as high-performance tracking agents for DC-based immunotherapies.

MRI Tracking of Dendritic Cells Loaded with Superparamagnetic Iron Oxide Nanoparticles

Cell tracking via MRI has drawn much attention recently for its sensitive, deep, and real-time properties and high spatial resolution. In a previous chapter, the labeling and tracking of superparamagnetic iron oxide (SPIO)-nanoparticle-loaded stem cells have been well summarized (Sykova et al., Methods Mol Biol 750:79-90, 2011). Thus, in this chapter, we will mainly focus on the tracking of SPIO-nanoparticle-labeled mouse dendritic cells by MRI and provide a detailed protocol for cell labeling and in vivo tracking by a clinical 3.0T MRI scanner. Of note, this protocol is also suitable to be applied on other types of cells.

Bioactive iron oxide nanoparticles suppress osteoclastogenesis and ovariectomy-induced bone loss through regulating the TRAF6-p62-CYLD signaling complex

Iron oxide nanoparticles (IONPs) have been widely used as contrast agents for magnetic resonance imaging (MRI) and other biomedical applications in both clinical and preclinical cases. In the present study, we show that two clinically used IONPs, ferumoxytol and ferucarbotran, have an intrinsic inhibitory effect on receptor activator NF-κB ligand (RANKL)-induced osteoclastogenesis of bone marrow-derived monocytes/macrophages (BMMs). IONPs significantly inhibited the formation of tartrate-resistant acid phosphatase (TRAP)-positive multinuclear osteoclasts and functional actin ring structures. More importantly, the inhibitory effect was also verified in vivo by its capacity to rescue the bone loss of ovariectomized (OVX) mice after intravenous injection with IONPs. Mechanistically, we found that IONPs trigger the upregulation of p62 which result in recruitment of CYLD and enhanced deubiquitination of TRAF6, a master controller of RANKL signaling. The downstream activation of NF-κB and MAPK signals was accordingly attenuated, ultimately leading to reduced expression of osteoclatogenesis-related genes. Taken together, clinically used IONPs can inhibit osteoclastogenesis through regulating TRAF6-p62-CYLD signaling complex, and they may be considered as alternative options for treatment of osteoporosis. STATEMENT OF SIGNIFICANCE: Nanoparticles have been developed as drug delivery systems for treatment of osteoporosis, mostly an age-related health problem with risk of fractures. In this work, we show that two clinically used iron oxide nanoparticles (IONPs) ferumoxytol and ferucarbotran themselves can significantly reduce the osteoporosis of ovariectomized (OVX) mice through inhibiting Osteoclastogenesis. We found that IONPs trigger the upregulation of p62 which result in recruitment of CYLD and enhanced deubiquitination of TRAF6, a master controller of RANKL signaling. The downstream activation of NF-κB and MAPK signals was accordingly attenuated, leading to reduced expression of osteoclatogenesis-related genes. Taken together, clinically used IONPs inhibit osteoclastogenesis through regulating TRAF6-p62-CYLD signaling complex, and they may be considered as alternative options for treatment of osteoporosis.

Magnetic Nanoparticles Attached to the NK Cell Surface for Tumor Targeting in Adoptive Transfer Therapies Does Not Affect Cellular Effector Functions

Adoptive cell transfer therapy is currently one of the most promising approaches for cancer treatment. This therapy has some limitations, however, such as the dispersion of in vivo-administered cells, causing only a small proportion to reach the tumor. Nanotechnological approaches could offer a solution for this drawback, as they can increase cell retention and accumulation in a region of interest. In particular, strategies employing magnetic nanoparticles (MNPs) to improve targeting of adoptively transferred T or NK cells have been explored in mice. In vivo magnetic retention is reported using the human NK cell line NK-92MI transfected with MNPs. Primary NK cells are nonetheless highly resistant to transfection, and thus we explore in here the possibility of attaching the MNPs to the NK cell surface to overcome this issue, and examine whether this association would affect NK effector functions. We assessed the attachment of MNPs coated with different polymers to the NK cell surface, and found that APS-MNP attached more efficiently to the NK-92MI cell surface. In association with MNPs, these cells preserved their main functions, exhibiting a continued capacity to degranulate, conjugate with and lyse target cells, produce IFN-γ, and respond to chemotactic signals. MNP-loaded NK-92MI cells were also retained in an in vitro capillary flow system by applying an EMF. A similar analysis was carried out in primary NK cells, isolated from mice, and expanded in vitro. These primary murine NK cells also maintained their functionality intact after MNP treatment and were successfully retained in vitro. This work therefore provides further support for using MNPs in combination with EMFs to favor specific retention of functional NK cells in a region of interest, which may prove beneficial to adoptive cell-therapy protocols.

Entry-Prohibited Effect of kHz Pulsed Magnetic Field Upon Interaction Between SPIO Nanoparticles and Mesenchymal Stem Cells

OBJECTIVE

The interaction between superparamagnetic iron oxide (SPIO) nanoparticles and mesenchymal stem cells (MSCs) in the presence of pulsed magnetic field (PMF) has become an important area of research in recent years.

METHODS

A parameter-adjustable pulsed magnetic field was developed based on the principle of insulated gate bipolar translator transistor-controlled discharge of large capacitances. The internalizations of SPIO nanoparticles by MSCs were investigated under the treatment of PMF in both intermittent stimulation mode and continuous stimulation mode.

RESULTS

The intensities and frequencies of pulsed magnetic field can be adjustable in the range of 1.9-4.6 mT and 3-5 kHz, respectively. This PMF was safe to the MSCs. However, the uptake of SPIO nanoparticles by MSCs was significantly prohibited under the treatment of kHz-ranged PMF while the 10 Hz PMF enhanced the cellular uptake of nanoparticles. This phenomenon was relative with the magnetic effect of the PMF with different frequency.

CONCLUSION

The PMF can be used to effectively regulate the cellular uptake of SPIO nanoparticles and the mechanism lies in the magnetic effect.

SIGNIFICANCE

The interaction between SPIO nanoparticles and the MSCs is a fundamental and important issue for nanomedicine and stem cell research. Our results demonstrate that the external magnetic field can be used to regulate their interaction. We believe that this safe, facile, and flexible method will greatly promote the development and clinical translation of regenerative medicine and nanomedicine.

T cells loaded with magnetic nanoparticles are retained in peripheral lymph nodes by the application of a magnetic field

Background

T lymphocytes are highly dynamic elements of the immune system with a tightly regulated migration. T cell-based transfer therapies are promising therapeutic approaches which in vivo efficacy is often limited by the small proportion of administered cells that reaches the region of interest. Manipulating T cell localisation to improve specific targeting will increase the effectiveness of these therapies. Nanotechnology has been successfully used for localized release of drugs and biomolecules. In particular, magnetic nanoparticles (MNPs) loaded with biomolecules can be specifically targeted to a location by an external magnetic field (EMF). The present work studies whether MNP-loaded T cells could be targeted and retained in vitro and in vivo at a site of interest with an EMF.

Results

T cells were unable to internalize the different MNPs used in this study, which remained in close association with the cell membrane. T cells loaded with an appropriate MNP concentration were attracted to an EMF and retained in an in vitro capillary flow-system. MNP-loaded T cells were also magnetically retained in the lymph nodes after adoptive transfer in in vivo models. This enhanced in vivo retention was in part due to the EMF application and to a reduced circulating cell speed within the organ. This combined use of MNPs and EMFs did not alter T cell viability or function.

Conclusions

These studies reveal a promising approach to favour cell retention that could be implemented to improve cell-based therapy.

Electronic supplementary material

The online version of this article (10.1186/s12951-019-0440-z) contains supplementary material, which is available to authorized users.

Very small superparamagnetic iron oxide nanoparticles: Long-term fate and metabolic processing in atherosclerotic mice

We investigated the biotransformation of very small superparamagnetic iron oxide nanoparticles (VSOP) in atherosclerotic LDLR^-/- mice. Transmission electron microscopy revealed an uptake of VSOP not only by macrophages but also by endothelial cells in liver, spleen, and atherosclerotic lesions and their accumulation in the lysosomal compartment. Using magnetic particle spectroscopy (MPS), we show that the majority of VSOP's superparamagnetic iron was degraded within 28 days. MPS spectrum shape indicated changes in the magnetic properties of VSOP during the biodegradation process. Experiments with primary murine bone marrow derived macrophages, primary murine liver sinusoidal endothelial cells, and primary human aortic endothelial cells demonstrated that loading with VSOP induced a differential response of cellular iron homeostasis mechanisms with increased levels of ferritin and iron transport proteins in macrophages and increased levels of ferritin in endothelial cells.

Lactosylated N-Alkyl polyethylenimine coated iron oxide nanoparticles induced autophagy in mouse dendritic cells

Dendritic cell (DC)-based vaccines have shown promising therapeutic results in cancer and some immune disorders. It is critical to track in vivo migration behaviours of DCs and monitor the whole process dynamically and non-invasively. Superparamagnetic iron oxide (SPIO) nanoparticles are chosen for DC labelling under magnetic resonance imaging (MRI) because of their proven biosafety as contrast agents. However, when used for cell labelling, sensitive biological indicators such as cell autophagy may be helpful to better understand the process and improve the probe design. Here, lactosylated N-Alkyl polyethylenimine coated SPIO nanoparticles are used for DC labelling. This probe shows satisfactory cell labelling efficiency and low cytotoxicity. In this study, autophagy was used as a key factor to understand how DCs react to nanoparticles after labelling. Our results demonstrate that the nanoparticles can induce protective autophagy in DCs, as inhibition of the autophagy flux could lead to cell death. Meanwhile, the nanoparticles induced autophagy could promote DC maturation which is an essential process for its migration and antigen presentation. Autophagy induced DC maturation is known to enhance the vaccine functions of DCs, therefore, our results suggest that beyond the MRI tracking ability, this probe might enhance therapeutic immune activation as well.

Nanoparticle-based strategies for cancer immunotherapy and immunodiagnostics

Although recent successes in clinical trials are strengthening research focused on cancer immunology, the poor immunogenicity and off-target side effects of immunotherapeutics remain major challenges in translating these promising approaches to clinically feasible therapies in the treatment of a large range of tumors. Nanotechnology offers target-based approaches, which have shown significant improvements in the rapidly advancing field of cancer immunotherapy. Here, we first discuss the chemical and physical features of nanoparticulate systems that can be tuned to address the anticancer immune response, and then review recent, key examples of the exploited strategies, ranging from nanovaccines to NPs revising the tumor immunosuppressive microenvironment, up to immunotherapeutic multimodal NPs. Finally, the paper concludes by identifying the promising and outstanding challenges the field of emerging nanotechnologies is facing for cancer immunotherapy.

Green Synthesis of Sub-10 nm Gadolinium-Based Nanoparticles for Sparkling Kidneys, Tumor, and Angiogenesis of Tumor-Bearing Mice in Magnetic Resonance Imaging

Gadolinium (Gd)-based nanoparticles are known for their high potential in magnetic resonance imaging (MRI). However, further MRI applications of these nanoparticles are hampered by their relatively large sizes resulting in poor organ/tumor targeting. In this study, ultrafine sub-10 nm and biocompatible Gd-based nanoparticles are synthesized in a bioinspired, environmentally benign, and straightforward fashion. This novel green synthetic strategy is developed for growing dextran-coated Gd-based nanoparticles (GdNPs@Dex). The as-prepared GdNPs@Dex is not only biocompatible but also stable with a sub-10 nm size. It exhibits higher longitudinal and transverse relaxivities in water (r₁ and r₂ values of 5.43 and 7.502 s^-1 × 10^-3 m^-1 of Gd³⁺ , respectively) than those measured for Gd-DTPA solution (r₁ and r₂ values of 3.42 and 3.86 s^-1 × 10^-3 m^-1 of Gd³⁺ , respectively). In vivo dynamic T₁ -weighted MRI in tumor-bearing mice shows GdNPs@Dex can selectively target kidneys and tumor, in addition to liver and spleen. GdNPs@Dex is found particularly capable for determining the tumor boundary with clearly enhanced tumor angiogenesis. GdNPs@Dex is also found cleared from body gradually mainly via hepatobiliary and renal processing with no obvious systemic toxicity. With this green synthesis strategy, the sub-10 nm GdNPs@Dex presents promising potentials for translational biomedical imaging applications.

Poly(ethylene glycol) modified Mn2+ complexes as contrast agents with a prolonged observation window in rat MRA

PEGylated Mn²⁺ complexes show higher relaxivity and longer blood circulation time than free Mn²⁺ complexes.

Advances in Molecular Imaging Strategies for In Vivo Tracking of Immune Cells

Tracking of immune cells in vivo is a crucial tool for development and optimization of cell-based therapy. Techniques for tracking immune cells have been applied widely for understanding the intrinsic behavior of immune cells and include non-radiation-based techniques such as optical imaging and magnetic resonance imaging (MRI), radiation-based techniques such as computerized tomography (CT), and nuclear imaging including single photon emission computerized tomography (SPECT) and positron emission tomography (PET). Each modality has its own strengths and limitations. To overcome the limitations of each modality, multimodal imaging techniques involving two or more imaging modalities are actively applied. Multimodal techniques allow integration of the strengths of individual modalities. In this review, we discuss the strengths and limitations of currently available preclinical in vivo immune cell tracking techniques and summarize the value of immune cell tracking in the development and optimization of immune cell therapy for various diseases.

Reduction of polyethylenimine-coated iron oxide nanoparticles induced autophagy and cytotoxicity by lactosylation

Superparamagnetic iron oxide (SPIO) nanoparticles are excellent magnetic resonance contrast agents and surface engineering can expand their applications. When covered with amphiphilic alkyl-polyethyleneimine (PEI), the modified SPIO nanoparticles can be used as MRI visible gene/drug delivery carriers and cell tracking probes. However, the positively charged amines of PEI can also cause cytotoxicity and restricts their further applications. In this study, we used lactose to modify amphiphilic low molecular weight polyethylenimine (C12-PEI2K) at different lactosylation degree. It was found that the N-alkyl-PEI-lactobionic acid wrapped SPIO nanocomposites show better cell viability without compromising their labelling efficacy as well as MR imaging capability in RAW 264.7 cells, comparing to the unsubstituted ones. Besides, we found the PEI induced cell autophagy can be reduced via lactose modification, indicating the increased cell viability might rely on down-regulating autophagy. Thus, our findings provide a new approach to overcome the toxicity of PEI wrapped SPIO nanocomposites by lactose modification.

Self-assembled dual-modality contrast agents for non-invasive stem cell tracking via near-infrared fluorescence and magnetic resonance imaging

Stem cells hold great promise for treating various diseases. However, one of the main drawbacks of stem cell therapy is the lack of non-invasive image-tracking technologies. Although magnetic resonance imaging (MRI) and near-infrared fluorescence (NIRF) imaging have been employed to analyse cellular and subcellular events via the assistance of contrast agents, the sensitivity and temporal resolution of MRI and the spatial resolution of NIRF are still shortcomings. In this study, superparamagnetic iron oxide nanocrystals and IR-780 dyes were co-encapsulated in stearic acid-modified polyethylenimine to form a dual-modality contrast agent with nano-size and positive charge. These resulting agents efficiently labelled stem cells and did not influence the cellular viability and differentiation. Moreover, the labelled cells showed the advantages of dual-modality imaging in vivo.

In Vivo Tracking of Phagocytic Immune Cells Using a Dual Imaging Probe with Gadolinium-Enhanced MRI and Near-Infrared Fluorescence

A novel dual imaging probe for in vivo magnetic resonance imaging (MRI) and optical imaging was developed by combining gadolinium (Gd)-chelating MR probe and a near-infrared (NIR) fluorophore, aza-BODIPY (AB; BODIPY = boron-dipyrromethene). This aza-BODIPY-based bimodal contrast agent (AB-BCA) showed a significant fluorescence emission around the NIR range and an enhanced longitudinal relaxivity in MR modality. The probe was easily delivered to phagocytic cells of the innate immune system, together with macrophages and dendritic cells (DCs), and presented high-performance fluorescence and MR imaging without obvious cytotoxicity. For in vivo visualization of AB-BCA using MRI and optical imaging, bone marrow-derived DCs were labeled and injected into the footpad of mice, and labeled DCs were tracked in vivo. We observed the migration of AB-BCA-labeled DCs into the lymph nodes via lymphatic vessels using NIR fluorescence and T1-weighted MR images. This dual-modality imaging probe was used for noninvasive monitoring of DC migration into lymph nodes and could be useful for investigating advanced cellular immunotherapy.

Synthesis of sub-100 nm biocompatible superparamagnetic Fe3O4 colloidal nanocrystal clusters as contrast agents for magnetic resonance imaging

Sub-100 nm Fe₃O₄ particles have been synthesized via a solvothermal method by using water as a size-control agent. They show superparamagnetism, high magnetization, prominent biocompatibility, and great promising for magnetic resonance imaging.

A Protein-Corona-Free T(1)-T(2) Dual-Modal Contrast Agent for Accurate Imaging of Lymphatic Tumor Metastasis

Precise nodal staging is particularly important to guide the treatments and determine the prognosis for cancer patients. However, it is still challenging to noninvasively and precisely detect in-depth tumor metastasis in lymph nodes (LNs) because of the small size and high potential of obtaining pseudopositive results. Herein, we report the rational design of a T1-T2 dual-modal MRI contrast agent for accurate imaging of tumor metastasis in LNs using gadolinium-embedded iron oxide nanoplates (GdIOP). The GdIOP were modulated with suitable size in vivo through surface functionalization by zwitterionic dopamine sulfonate (ZDS) molecules. The efficient uptake of GdIOP@ZDS nanoparticles through drainage effect because of the presence of large amount of macrophages and dendritic cells generates both T1 and T2 contrasts in LNs. In contrast, the low uptake of protein-corona-free GdIOP@ZDS nanoparticles by melanoma B16 tumor cells promises pseudocontrast imaging of potential tumor metastasis in LNs. The combination of T1 and T2 imaging modalities allows self-confirmed detection of a metastatic tumor with about 1.2 mm in the minimal dimension in LNs, which is close to the detection limit of submilimeter level of MRI scans. This study provides an efficient and noninvasive strategy to detect tumor metastasis in LNs with greatly enhanced diagnostic accuracy.