Cellular magnetic resonance imaging using superparamagnetic anionic iron oxide nanoparticles: applications to in vivo trafficking of lymphocytes and cell-based anticancer therapy

Non-invasive cell-tracking methods for adoptive T cell therapies

Adoptive T cell therapies (ACT) have demonstrated groundbreaking results in blood cancers and melanoma. Nevertheless, their significant cost, the occurrence of severe adverse events, and their poor performance in solid tumors are important hurdles hampering more widespread applicability. In vivo cell tracking allows instantaneous and non-invasive monitoring of the distribution, tumor homing, persistence, and redistribution to other organs of infused T cells in patients. Furthermore, cell tracking could aid in the clinical management of patients, allowing the detection of non-responders or severe adverse events at an early stage. This review provides a concise overview of the main principles and potential of cell tracking, followed by a discussion of the clinically relevant labeling strategies and their application in ACT.

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.

Cell Tracking in Cancer Immunotherapy

The impressive development of cancer immunotherapy in the last few years originates from a more precise understanding of control mechanisms in the immune system leading to the discovery of new targets and new therapeutic tools. Since different stages of disease progression elicit different local and systemic inflammatory responses, the ability to longitudinally interrogate the migration and expansion of immune cells throughout the whole body will greatly facilitate disease characterization and guide selection of appropriate treatment regiments. While using radiolabeled white blood cells to detect inflammatory lesions has been a classical nuclear medicine technique for years, new non-invasive methods for monitoring the distribution and migration of biologically active cells in living organisms have emerged. They are designed to improve detection sensitivity and allow for a better preservation of cell activity and integrity. These methods include the monitoring of therapeutic cells but also of all cells related to a specific disease or therapeutic approach. Labeling of therapeutic cells for imaging may be performed in vitro, with some limitations on sensitivity and duration of observation. Alternatively, in vivo cell tracking may be performed by genetically engineering cells or mice so that may be revealed through imaging. In addition, SPECT or PET imaging based on monoclonal antibodies has been used to detect tumors in the human body for years. They may be used to detect and quantify the presence of specific cells within cancer lesions. These methods have been the object of several recent reviews that have concentrated on technical aspects, stressing the differences between direct and indirect labeling. They are briefly described here by distinguishing ex vivo (labeling cells with paramagnetic, radioactive, or fluorescent tracers) and in vivo (in vivo capture of injected radioactive, fluorescent or luminescent tracers, or by using labeled antibodies, ligands, or pre-targeted clickable substrates) imaging methods. This review focuses on cell tracking in specific therapeutic applications, namely cell therapy, and particularly CAR (Chimeric Antigen Receptor) T-cell therapy, which is a fast-growing research field with various therapeutic indications. The potential impact of imaging on the progress of these new therapeutic modalities is discussed.

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.

Easy and Efficient Cell Tagging with Block Copolymer-Based Contrast Agents for Sensitive MRI Detection in Vivo

Superparamagnetic iron oxide nanoparticles (MNPs) together with magnetic resonance imaging (MRI) are the preferred tools for monitoring the fate and biodistribution of administered cells in stem cell therapy studies. Commercial MNPs need transfection agents and long incubation times for sufficient cell labeling and further in vivo cell detection. In this work, we have synthesized MNPs coated with pluronic F127 and tetronic 908, and validated their applicability as contrast agents for MRI cell detection on two different cell types: rat mesenchymal stem cells (MSCs) and multipotent neural progenitor cell line from mice (C17.2). No transfection agent was needed for a complete MNP internalization, and the uptake was only dependent on MNP concentration in medium and limited on the incubation time. By combining in vivo MRI and ex vivo histology microscopy, we have demonstrated the MRI signal detected corresponded exclusively to labeled cells and not to free particles. Pluronic F127- and tetronic 908-coated MNPs represent promising contrast agents for stem cell tracking due to their ease of use in preparation, their efficiency for cell labeling, and their high sensitivity for in vivo cell detection.

Development of individualized anti-metastasis strategies by engineering nanomedicines

Metastasis is deadly and also tough to treat as it is much more complicated than the primary tumour. Anti-metastasis approaches available so far are far from being optimal. A variety of nanomedicine formulae provide a plethora of opportunities for developing new strategies and means for tackling metastasis. It should be noted that individualized anti-metastatic nanomedicines are different from common anti-cancer nanomedicines as they specifically target different populations of malignant cells. This review briefly introduces the features of the metastatic cascade, and proposes a series of nanomedicine-based anti-metastasis strategies aiming to block each metastatic step. Moreover, we also concisely introduce the advantages of several promising nanoparticle platforms and their potential for constructing state-of-the-art individualized anti-metastatic nanomedicines.

Nanomaterial applications in multiple sclerosis inflamed brain

In the last years scientific progress in nanomaterials, where size and shape make the difference, has increased their utilization in medicine with the development of a promising new translational science: nanomedicine. Due to their surface and core biophysical properties, nanomaterials hold the promise for medical applications in central nervous system (CNS) diseases: inflammatory, degenerative and tumors. The present review is focused on nanomaterials at the neuro-immune interface, evaluating two aspects: the possible CNS inflammatory response induced by nanomaterials and the developments of nanomaterials to improve treatment and diagnosis of neuroinflammatory diseases, with a focus on multiple sclerosis (MS). Indeed, nanomedicine allows projecting new ways of drug delivery and novel techniques for CNS imaging. Despite the wide field of application in neurological diseases of nanomaterials, our topic here is to review the more recent development of nanomaterials that cross blood brain barrier (BBB) and reach specific target during CNS inflammatory diseases, a crucial strategy for CNS early diagnosis and drug delivery, indeed the main challenges of nanomedicine.

Highly Efficient Labeling of Human Lung Cancer Cells Using Cationic Poly-l-lysine-Assisted Magnetic Iron Oxide Nanoparticles

Cell labeling with magnetic iron oxide nanoparticles (IONPs) is increasingly a routine approach in the cell-based cancer treatment. However, cell labeling with magnetic IONPs and their leading effects on the biological properties of human lung carcinoma cells remain scarcely reported. Therefore, in the present study the magnetic γ-Fe₂O₃ nanoparticles (MNPs) were firstly synthesized and surface-modified with cationic poly-l-lysine (PLL) to construct the PLL-MNPs, which were then used to magnetically label human A549 lung cancer cells. Cell viability and proliferation were evaluated with propidium iodide/fluorescein diacetate double staining and standard 3-(4,5-dimethylthiazol-2-diphenyl-tetrazolium) bromide assay, and the cytoskeleton was immunocytochemically stained. The cell cycle of the PLL-MNP-labeled A549 lung cancer cells was analyzed using flow cytometry. Apoptotic cells were fluorescently analyzed with nuclear-specific staining after the PLL-MNP labeling. The results showed that the constructed PLL-MNPs efficiently magnetically labeled A549 lung cancer cells and that, at low concentrations, labeling did not affect cellular viability, proliferation capability, cell cycle, and apoptosis. Furthermore, the cytoskeleton in the treated cells was detected intact in comparison with the untreated counterparts. However, the results also showed that at high concentration (400 µg mL^-1), the PLL-MNPs would slightly impair cell viability, proliferation, cell cycle, and apoptosis and disrupt the cytoskeleton in the treated A549 lung cancer cells. Therefore, the present results indicated that the PLL-MNPs at adequate concentrations can be efficiently used for labeling A549 lung cancer cells and could be considered as a feasible approach for magnetic targeted anti-cancer drug/gene delivery, targeted diagnosis, and therapy in lung cancer treatment.

Compare analysis for the nanotoxicity effects of different amounts of endocytic iron oxide nanoparticles at single cell level

Developing methods that evaluate the cellular uptake of magnetic nanoparticles (MNPs) and nanotoxicity effects at single-cellular level are needed. In this study, magnetophoresis combining fluorescence based cytotoxicity assay was proposed to assess the viability and the single-cellular MNPs uptake simultaneously. Malignant cells (SKHep-1, HepG2, HeLa) were incubated with 10 nm anionic iron oxide nanoparticles. Prussian blue stain was performed to visualize the distribution of magnetic nanoparticles. MTT and fluorescence based assay analyzed the cytotoxicity effects of the bulk cell population and single cell, respectively. DAPI/PI stained was applied to evaluate death mechanism. The number of intracellular MNPs was found to be strongly correlated with the cell death. Significant differences between cellular MNP uptake in living and dead cells were observed. The method could be useful for future study of the nanotoxicity induced by MNPs.

MRI contrast variation of thermosensitive magnetoliposomes triggered by focused ultrasound: a tool for image-guided local drug delivery

Improved drug delivery control during chemotherapy has the potential to increase the therapeutic index. MRI contrast agent such as iron oxide nanoparticles can be co-encapsulated with drugs in nanocarrier liposomes allowing their tracking and/or visualization by MRI. Furthermore, the combination of a thermosensitive liposomal formulation with an external source of heat such as high intensity focused ultrasound guided by MR temperature mapping allows the controlled local release of the content of the liposome. MRI-guided high-intensity focused ultrasound (HIFU), in combination represents a noninvasive technique to generate local hyperthermia for drug release. In this study we used ultrasmall superparamagnetic iron oxide nanoparticles (USPIO) encapsulated in thermosensitive liposomes to obtain thermosensitive magnetoliposomes (TSM). The transverse and longitudinal relaxivities of this MRI contrast agent were measured upon TSM membrane phase transition in vitro using a water bath or HIFU. The results showed significant differences for MRI signal enhancement and relaxivities before and after heating, which were absent for nonthermosensitive liposomes and free nanoparticles used as controls. Thus, incorporation of USPIO as MRI contrast agents into thermosensitive liposomes should, besides TSM tumor accumulation monitoring, allow the visualization of TSM membrane phase transition upon temperature elevation. In conclusion, HIFU under MR image guidance in combination with USPIO-loaded thermosensitive liposomes as drug delivery system has the potential for a better control of drug delivery and to increase the drug therapeutic index.

Magnetic and degradable polymer/bioactive glass composite nanoparticles for biomedical applications

The present study focuses on the development of a biocompatible and biodegradable iron oxide incorporated chitosan-gelatin bioglass composite nanoparticles [Fe-BG]. The developed composite nanoparticle was analyzed by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy, thermo gravimetric analysis (TG) and differential scanning calorimetry analysis (DSC). The size of the negatively charged composite nanoparticle was in the range of 43-51 nm. The in vitro analysis of the composite nanoparticles was carried out by cell aggregation, protein adsorption and haemolytic activity. The magnetic hysteresis value of the composite nanoparticle showed that it is a soft magnetic material. The presence of iron oxide in the chitosan-gelatin bioglass [BG] matrix enhances biodegradability as indicated in the TG studies. Iron-oxide in equal amount to bioglass in the polymer matrix has been obtained as the optimized system. The developed composite nanoparticle is a soft magnetic material and is suitable for the magnetic hyperthermia treatment and drug delivery. More detailed in vivo studies are needed to confirm the biodegradation profile and biological activity of the material.

Superparamagnetic iron oxide (SPIO) labeling efficiency and subsequent MRI tracking of native cell populations pertinent to pulmonary heart valve tissue engineering studies

The intimal and medial linings of the pulmonary artery consist largely of vascular endothelial cells (VECs) and vascular smooth muscle cells (VSMCs), respectively. The migration of these cell types to a potential tissue-engineered pulmonary valve (TEPV) implant process is therefore of interest in understanding the valve remodeling process. Visualization and cell tracking by MRI, which employs hypointense contrast achievable through the use of superparamagnetic iron oxide (SPIO) microparticles to label cells, provides a method in which this can be studied. We investigated the SPIO labeling efficiency of human VECs and VSMCs, and used two- and three-dimensional gradient echo sequences to track the migration of these cells in agar gel constructs. Protamine sulfate (4.5 µg/mL) was used to enhance SPIO uptake and was found to have no influence on cell viability or proliferation. MRI experiments were initially performed using a 9.4-T scanner. The results demonstrated that the spatial positions of hypointense spots were relatively unchanged over 12 days. Subsequent MR experiments performed at 7 T demonstrated that three-dimensional imaging provided the best spatial resolution to assess cell fate. R(2)* maps were bright in SPIO cell-encapsulated gels in comparison with unlabeled counterparts. Signal voids were ruled out as hypointense regions owing to the smooth exponential decay of T(2)* in these voxels. As a next step, we intend to use the SPIO cell labeling and MR protocols established in this study to assess whether hemodynamic stresses will alter the vascular cell migratory patterns. These studies will shed light on the mechanisms of vascular remodeling after TEPV implantation.

A new nano-sized iron oxide particle with high sensitivity for cellular magnetic resonance imaging

PURPOSE

In this study, we investigated the labeling efficiency and magnetic resonance imaging (MRI) signal sensitivity of a newly synthesized, nano-sized iron oxide particle (IOP) coated with polyethylene glycol (PEG), designed by Industrial Technology Research Institute (ITRI).

PROCEDURES

Macrophages, bone-marrow-derived dendritic cells, and mesenchymal stem cells (MSCs) were isolated from rats and labeled by incubating with ITRI-IOP, along with three other iron oxide particles in different sizes and coatings as reference. These labeled cells were characterized with transmission electron microscopy (TEM), light and fluorescence microscopy, phantom MRI, and finally in vivo MRI and ex vivo magnetic resonance microscopy (MRM) of transplanted hearts in rats infused with labeled macrophages.

RESULTS

The longitudinal (r (1)) and transverse (r (2)) relaxivities of ITRI-IOP are 22.71 and 319.2 s(-1) mM(-1), respectively. TEM and microscopic images indicate the uptake of multiple ITRI-IOP particles per cell for all cell types. ITRI-IOP provides sensitivity comparable or higher than the other three particles shown in phantom MRI. In vivo MRI and ex vivo MRM detect punctate spots of hypointensity in rejecting hearts, most likely caused by the accumulation of macrophages labeled by ITRI-IOP.

CONCLUSION

ITRI-IOP, the nano-sized iron oxide particle, shows high efficiency in cell labeling, including both phagocytic and non-phagocytic cells. Furthermore, it provides excellent sensitivity in T(2)*-weighted MRI, and thus can serve as a promising contrast agent for in vivo cellular MRI.

Pulsed magneto-motive ultrasound imaging to detect intracellular trafficking of magnetic nanoparticles

As applications of nanoparticles in medical imaging and biomedicine rapidly expand, the interactions of nanoparticles with living cells have become an area of active interest. For example, intracellular accumulation of nanoparticles-an important part of cell-nanoparticle interaction-has been well studied using plasmonic nanoparticles and optical or optics-based techniques due to the change in optical properties of the nanoparticle aggregates. However, magnetic nanoparticles, despite their wide range of clinical applications, do not exhibit plasmonic-resonant properties and therefore their intracellular aggregation cannot be detected by optics-based imaging techniques. In this study, we investigated the feasibility of a novel imaging technique-pulsed magneto-motive ultrasound (pMMUS)-to identify intracellular accumulation of endocytosed magnetic nanoparticles. In pMMUS imaging a focused, high intensity, pulsed magnetic field is used to excite the cells labeled with magnetic nanoparticles, and ultrasound imaging is then used to monitor the mechanical response of the tissue. We demonstrated previously that clusters of magnetic nanoparticles amplify the pMMUS signal in comparison to the signal from individual nanoparticles. Here we further demonstrate that pMMUS imaging can identify interaction between magnetic nanoparticles and living cells, i.e. intracellular accumulation of nanoparticles within the cells. The results of our study suggest that pMMUS imaging can not only detect the presence of magnetic nanoparticles but also provides information about their intracellular accumulation non-invasively and in real-time.

In vivo imaging of pancreatic tumours and liver metastases using 7 Tesla MRI in a murine orthotopic pancreatic cancer model and a liver metastases model

Background

Pancreatic cancer is the fourth leading cause of tumour death in the western world. However, appropriate tumour models are scarce. Here we present a syngeneic murine pancreatic cancer model using 7 Tesla MRI and evaluate its clinical relevance and applicability.

Methods

6606PDA murine pancreatic cancer cells were orthotopically injected into the pancreatic head. Liver metastases were induced through splenic injection. Animals were analyzed by MRI three and five weeks following injection. Tumours were detected using T2-weighted high resolution sequences. Tumour volumes were determined by callipers and MRI. Liver metastases were analyzed using gadolinium-EOB-DTPA and T1-weighted 3D-Flash sequences. Tumour blood flow was measured using low molecular gadobutrol and high molecular gadolinium-DTPA.

Results

MRI handling and applicability was similar to human systems, resolution as low as 0.1 mm. After 5 weeks tumour volumes differed significantly (p < 0.01) when comparing calliper measurments (n = 5, mean 1065 mm³+/-243 mm³) with MRI (mean 918 mm³+/-193 mm³) with MRI being more precise. Histology (n = 5) confirmed MRI tumour measurements (mean size MRI 38.5 mm²+/-22.8 mm² versus 32.6 mm²+/-22.6 mm² (histology), p < 0,0004) with differences due to fixation and processing of specimens. After splenic injection all mice developed liver metastases with a mean of 8 metastases and a mean volume of 173.8 mm³+/-56.7 mm³ after 5 weeks. Lymphnodes were also easily identified. Tumour accumulation of gadobutrol was significantly (p < 0.05) higher than gadolinium-DTPA. All imaging experiments could be done repeatedly to comply with the 3R-principle thus reducing the number of experimental animals.

Conclusions

This model permits monitoring of tumour growth and metastasis formation in longitudinal non-invasive high-resolution MR studies including using contrast agents comparable to human pancreatic cancer. This multidisciplinary environment enables radiologists, surgeons and physicians to further improve translational research and therapies of pancreatic cancer.

Multi-functional magnetic nanoparticles for magnetic resonance imaging and cancer therapy

We have developed a multi-layer approach for the synthesis of water-dispersible superparamagnetic iron oxide nanoparticles for hyperthermia, magnetic resonance imaging (MRI) and drug delivery applications. In this approach, iron oxide core nanoparticles were obtained by precipitation of iron salts in the presence of ammonia and provided β-cyclodextrin and pluronic polymer (F127) coatings. This formulation (F127250) was highly water dispersible which allowed encapsulation of the anti-cancer drug(s) in β-cyclodextrin and pluronic polymer for sustained drug release. The F127250 formulation has exhibited superior hyperthermia effects over time under alternating magnetic field compared to pure magnetic nanoparticles (MNP) and β-cyclodextrin coated nanoparticles (CD200). Additionally, the improved MRI characteristics were also observed for the F127250 formulation in agar gel and in cisplatin resistant ovarian cancer cells (A12780CP) compared to MNP and CD200 formulations. Furthermore, the drug-loaded formulation of F127250 exhibited many folds of imaging contrast properties. Due to the internalization capacity of the F127250 formulation, its curcumin-loaded formulation (F127250-CUR) exhibited almost equivalent inhibition effects on A2780CP (ovarian), MDA-MB-231 (breast), and PC-3 (prostate) cancer cells even though curcumin release was only 40%. The improved therapeutic effects were verified by examining molecular effects using Western blotting and transmission electron microscopic (TEM) studies. F127250-CUR also exhibited haemocompatibility, suggesting a nanochemo-therapeutic agent for cancer therapy.