Magnetic targeting of iron-oxide-labeled fluorescent hepatoma cells to the liver

Magnetic Cell Targeting for Cardiovascular Tissue Engineering

There is a critical need for novel approaches to translate cell therapy and regenerative medicine to clinical practice. Magnetic cell targeting with site specificity has started to open avenues in these fields as a potential therapeutic platform. Magnetic targeting is gaining popularity in the field of biomedicine due to its ability to concentrate and retain at a target site while minimizing deleterious effects at off-target sites. It is regarded as a relatively straightforward and safe approach for a wide range of therapeutic applications. This review discusses the latest advancements and approaches in magnetic cell targeting using endocytosed and surface-bound magnetic nanoparticles as well as in vivo tracking using magnetic resonance imaging (MRI). The most common form of magnetic nanoparticles is superparamagnetic iron oxide nanoparticles (SPION). The biodegradable and biocompatible properties of these magnetically responsive particles and capacity for rapid endocytosis into cells make them a breakthrough in targeted therapy. This review further discusses specific applications of magnetic targeting approaches in cardiovascular tissue engineering including myocardial regeneration, therapeutic angiogenesis, and endothelialization of implantable cardiovascular devices.

Magnetically empowered bone marrow cells as a micro-living motor can improve early hematopoietic reconstitution

BACKGROUND AIMS

Bone marrow-derived hematopoietic stem cell transplantation/hematopoietic progenitor cell transplantation (HSCT/HPCT) is widely used and one of the most useful treatments in clinical practice. However, the homing rate of hematopoietic stem cells/hematopoietic progenitor cells (HSCs/HPCs) by routine cell transfusion is quite low, influencing hematopoietic reconstitution after HSCT/HPCT.

METHODS

The authors developed a micro-living motor (MLM) strategy to increase the number of magnetically empowered bone marrow cells (ME-BMCs) homing to the bone marrow of recipient mice.

RESULTS

In the in vitro study, migration and retention of ME-BMCs were greatly improved in comparison with non-magnetized bone marrow cells, and the biological characteristics of ME-BMCs were well maintained. Differentially expressed gene analysis indicated that ME-BMCs might function through gene regulation. In the in vivo study, faster hematopoietic reconstitution was observed in ME-BMC mice, which demonstrated a better survival rate and milder symptoms of acute graft-versus-host disease after transplantation of allogeneic ME-BMCs.

CONCLUSIONS

This study demonstrated that ME-BMCs serving as MLMs facilitated the homing of HSCs/HPCs and eventually contributed to earlier hematopoietic reconstitution in recipients. These data might provide useful information for other kinds of cell therapies.

Magnetic implants in vivo guiding sorafenib liver delivery by superparamagnetic solid lipid nanoparticles

HYPOTHESIS

Solid lipid nanoparticles (SLNs), co-encapsulating superparamagnetic iron oxide nanoparticles and sorafenib, have been exploited for magnetic-guided drug delivery to the liver. Two different magnetic configurations, both comprising two small magnets, were under-skin implanted to investigate the effect of the magnetic field topology on the magnetic SLNP accumulation in liver tissues. A preliminary simulation analysis was performed to predict the magnetic field topography for each tested configuration.

EXPERIMENTS

SLNs were prepared using a hot homogenization approach and characterized using complementary techniques. Their in vitro biological behavior was assessed in HepG-2 liver cancer cells; wild-type mice were used for the in vivo study. The magnet configuration that resulted in a higher magnetic targeting efficiency was investigated by evaluating the iron content in homogenated murine liver tissues.

FINDINGS

SLNs, characterized by an average size smaller than 200 nm, retained their superparamagnetic behavior and relevant molecular resonance imaging properties as negative contrast agents. The evaluation of iron accumulation in the liver tissues was consistent with the magnetic induction profile of each magnet configuration, concurring with the results predicted by simulation analysis and obtained by measurements in living mice.

The effects of superparamagnetic iron oxide nanoparticles-labeled mesenchymal stem cells in the presence of a magnetic field on attenuation of injury after heart failure

Migration of stem cells after transplantation reduces their therapeutic effects. In this study, we hypothesized that superparamagnetic iron oxide nanoparticles (SPION)-labeled mesenchymal stem cells (MSCs) in the presence of magnetic field may have a capability to increase regenerative ability after heart failure (HF). A rat model of ISO (isoproterenol)-HF was established to investigate the effects of SPION-labeled MSCs on tissue regeneration in the presence and absence of magnetic field. Hydrodynamic size, shape, and formation of chemical bonds between SPION and polyethylene glycol (PEG) were measured using dynamic light scattering (DLS), transmission electron microscopy (TEM), and Fourier-transform infrared spectroscopy (FTIR). The MRI was used to monitor SPION-labeled MSCs in vivo. Cell and tissue uptake of nanoparticles were determined by Prussian blue staining, atomic absorption spectroscopy (AAS), and inductively coupled plasma spectroscopy (ICP). Purity of the MSCs, heart function, myocardial fibrosis, and histologic damage were evaluated using flow-cytometry, echocardiography, Masson's trichrome, and H&E staining respectively. Various spectroscopic and microscopic analyses revealed that hydrodynamic size of SPION was 40 ± 2 and their shape was spherical. FTIR confirmed the presence of PEG on the surface of nanoparticles. The presence of magnetic field significantly increased cell homing. Highly purified MSCs population was detected by flow-cytometry. Using SPION-labeled MSCs in the presence of magnetic field markedly improved heart function and myocardial hypertrophy and reduced fibrosis (p < 0.05). Collectively, our results demonstrated that SPION-labeled MSCs in the presence of magnetic field might contribute to regeneration after HF.

Magnetic Enhancement of Stem Cell-Targeted Delivery into the Brain Following MR-Guided Focused Ultrasound for Opening the Blood-Brain Barrier

Focused ultrasound (FUS)-mediated blood–brain barrier disruption (BBBD) can enable even large therapeutics such as stem cells to enter the brain from the bloodstream. However, the efficiency is relatively low. Our previous study showed that human neural progenitor cells (hNPCs) loaded with superparamagnetic iron oxide nanoparticles (SPIONs) in culture were attracted by an external magnetic field. In vivo, enhanced brain retention was observed near a magnet mounted on the skull in a rat model of traumatic brain injury, where BBBD also occurs. The goal of the current study was to determine whether magnetic attraction of SPION-loaded hNPCs would also enhance their retention in the brain after FUS-mediated BBBD. A small animal magnetic resonance imaging (MRI)-guided FUS system operating at 1.5 MHz was used to treat rats (∼120 g) without tissue damage or hemorrhage. Evidence of successful BBBD was validated with both radiologic enhancement of gadolinium on postsonication TI MRI and whole brain section visualization of Evans blue dye. The procedure was then combined with the application of a powerful magnet to the head directly after intravenous injection of the hNPCs. Validation of cells within the brain was performed by staining with Perls’ Prussian blue for iron and by immunohistochemistry with a human-specific antigen. By injecting equal numbers of iron oxide (SPIONs) and noniron oxide nanoparticles–loaded hNPCs, each labeled with a different fluorophore, we found significantly greater numbers of SPIONs-loaded cells retained in the brain at the site of BBBD as compared to noniron loaded cells. This result was most pronounced in regions of the brain closest to the skull (dorsal cortex) in proximity to the magnet surface. A more powerful magnet and a Halbach magnetic array resulted in more effective retention of SPION-labeled cells in even deeper brain regions such as the striatum and ventral cortex. There, up to 90% of hNPCs observed contained SPIONs compared to 60% to 70% with the less powerful magnet. Fewer cells were observed at 24 h posttreatment compared to 2 h (primarily in the dorsal cortex). These results demonstrate that magnetic attraction can substantially enhance the retention of stem cells after FUS-mediated BBBD. This procedure could provide a safer and less invasive approach for delivering stem cells to the brain, compared to direct intracranial injections, substantially reducing the risk of bleeding and infection.

Enhanced Homing Technique of Mesenchymal Stem Cells Using Iron Oxide Nanoparticles by Magnetic Attraction in Olfactory-Injured Mouse Models

Intranasal delivery of mesenchymal stem cells (MSCs) to the olfactory bulb is a promising approach for treating olfactory injury. Additionally, using the homing phenomenon of MSCs may be clinically applicable for developing therapeutic cell carriers. Herein, using superparamagnetic iron oxide nanoparticles (SPIONs) and a permanent magnet, we demonstrated an enhanced homing effect in an olfactory model. Superparamagnetic iron oxide nanoparticles with rhodamine B (IRBs) had a diameter of 5.22 ± 0.9 nm and ζ-potential of +15.2 ± 0.3 mV. IRB concentration of 15 µg/mL was injected with SPIONs into MSCs, as cell viability significantly decreased when 20 μg/mL was used (p ≤ 0.005) compared to in controls. The cells exhibited magnetic attraction in vitro. SPIONs also stimulated CXCR4 (C-X-C chemokine receptor type 4) expression and CXCR4-SDF-1 (Stromal cell-derived factor 1) signaling in MSCs. After injecting magnetized MSCs, these cells were detected in the damaged olfactory bulb one week after injury on one side, and there was a significant increase compared to when non-magnetized MSCs were injected. Our results suggest that SPIONs-labeled MSCs migrated to injured olfactory tissue through guidance with a permanent magnet, resulting in better homing effects of MSCs in vivo, and that iron oxide nanoparticles can be used for internalization, various biological applications, and regenerative studies.

Theranostic Hyaluronic Acid-Iron Micellar Nanoparticles for Magnetic-Field-Enhanced in vivo Cancer Chemotherapy

The delivery of therapeutic cancer agents using nanomaterials has recently attracted much attention. Although encouraging progress with chemotherapeutics has been made, tumor treatment response remains unsatisfactory. To address this concern, we constructed a new micellar nanocomplex by covalently conjugating hyaluronic acid (HA) with an iron oxide nanoparticle (IONP). When an external magnetic field was applied to the tumor area, HA-IONP specifically accumulated in the tumor, due to the strong IONP magnetism. In addition, HA was shown to bind to cluster determinant 44 (CD44), which is overexpressed on tumor cells. With combined magnetic, CD44, and enhanced permeability retention (EPR) targeting, the efficient delivery of HA-IONP to the tumor is expected to enhance cancer treatment efficiency. After encapsulation of the chemotherapy drug homocamptothecin (HCPT), the theranostic potency of HA-IONP/HCPT (HIH) was investigated both in vitro and in vivo. The improved tumor homing behavior of HIH was observed by magnetic resonance imaging (MRI) when an external magnetic field was used. Moreover, HIH showed remarkable tumor ablation efficiency, with magnetic targeting after 3 mg kg^-1 intravenous administration (equivalent dose of free HCPT), and the tumors almost disappeared after treatment. No obvious systemic toxicity was detected. This excellent biocompatibility and tumor targetability suggests that HIH is a promising theranostic nanocomplex with great translational potency. Application of the HA-IONP platform could also be extended to delivery of other hydrophobic chemotherapy drugs or phototherapy agents.

Evaluation of Tumor Treatment of Magnetic Nanoparticles Driven by Extremely Low Frequency Magnetic Field

Recently, magnetic nanoparticles (MNPs), which can be manipulated in the magnetic field, have received much attention in tumor therapy. Extremely low frequency magnetic field (ELMF) system can initiate MNPs vibrating and the movement of MNPs inside of cells can be controlled by adjusting the frequency and intensity of ELMF towards irreversible cell damages. In this study, we investigated the detrimental effects on tumor cells with MNPs under various ELMF exposure conditions. An in-house built ELMF system was developed and utilized for evaluating the treatment efficiency of MNPs on tumor cells with specific intensities (2–20 Hz) and frequencies (0.1–20 mT). Significant morphological changes were found in tumor cells treated with MNPs in combing with ELMF, which were consistent with noticeable decrease in cell viability. With the increase of the intensity and frequency of the magnetic field, the structural integrity of tumor tissue can be further destroyed. Destructive effects of MNPs and ELMF on tumor tissues were further determined by the pathophysiological changes observed in vivo in animal study. Taken together, the combination of MNPs and ELMF had a great potential as an innovative treatment approach for tumor intervention.

Magnetic Enrichment of Dendritic Cell Vaccine in Lymph Node with Fluorescent-Magnetic Nanoparticles Enhanced Cancer Immunotherapy

Dendritic cell (DC) migration to the lymph node is a key component of DC-based immunotherapy. However, the DC homing rate to the lymphoid tissues is poor, thus hindering the DC-mediated activation of antigen-specific T cells. Here, we developed a system using fluorescent magnetic nanoparticles (α-AP-fmNPs; loaded with antigen peptide, iron oxide nanoparticles, and indocyanine green) in combination with magnetic pull force (MPF) to successfully manipulate DC migration in vitro and in vivo. α-AP-fmNPs endowed DCs with MPF-responsiveness, antigen presentation, and simultaneous optical and magnetic resonance imaging detectability. We showed for the first time that α-AP-fmNP-loaded DCs were sensitive to MPF, and their migration efficiency could be dramatically improved both in vitro and in vivo through MPF treatment. Due to the enhanced migration of DCs, MPF treatment significantly augmented antitumor efficacy of the nanoparticle-loaded DCs. Therefore, we have developed a biocompatible approach with which to improve the homing efficiency of DCs and subsequent anti-tumor efficacy, and track their migration by multi-modality imaging, with great potential applications for DC-based cancer immunotherapy.

Cell Labeling and Targeting with Superparamagnetic Iron Oxide Nanoparticles

Targeted delivery of cells and therapeutic agents would benefit a wide range of biomedical applications by concentrating the therapeutic effect at the target site while minimizing deleterious effects to off-target sites. Magnetic cell targeting is an efficient, safe, and straightforward delivery technique. Superparamagnetic iron oxide nanoparticles (SPION) are biodegradable, biocompatible, and can be endocytosed into cells to render them responsive to magnetic fields. The synthesis process involves creating magnetite (Fe3O4) nanoparticles followed by high-speed emulsification to form a poly(lactic-co-glycolic acid) (PLGA) coating. The PLGA-magnetite SPIONs are approximately 120 nm in diameter including the approximately 10 nm diameter magnetite core. When placed in culture medium, SPIONs are naturally endocytosed by cells and stored as small clusters within cytoplasmic endosomes. These particles impart sufficient magnetic mass to the cells to allow for targeting within magnetic fields. Numerous cell sorting and targeting applications are enabled by rendering various cell types responsive to magnetic fields. SPIONs have a variety of other biomedical applications as well including use as a medical imaging contrast agent, targeted drug or gene delivery, diagnostic assays, and generation of local hyperthermia for tumor therapy or tissue soldering.

Cell-Based Therapy in TBI: Magnetic Retention of Neural Stem Cells In Vivo

Stem cell therapy is under active investigation for traumatic brain injury (TBI). Noninvasive stem cell delivery is the preferred method, but retention of stem cells at the site of injury in TBI has proven challenging and impacts effectiveness. To investigate the effects of applying a magnetic field on cell homing and retention, we delivered human neuroprogenitor cells (hNPCs) labeled with a superparamagnetic nanoparticle into post-TBI animals in the presence of a static magnetic field. We have previously devised a method of loading hNPCs with ultrasmall superparamagnetic iron oxide (USPIO) nanoparticles Molday ION Rhodamine B (MIRB™). Labeling of hNPCs (MIRB-hNPCs) does not affect hNPC viability, proliferation, or differentiation. The 0.6 tesla (T) permanent magnet was placed ∼4 mm above the injured parietal cortex prior to intracarotid injection of 4 × 10(4) MIRB-hNPCs. Fluorescence imaging, Perls' Prussian blue histochemistry, immunocytochemistry with SC121, a human-specific antibody, and T2-weighted magnetic resonance imaging ex vivo revealed there was increased homing and retention of MIRB-hNPCs in the injured cortex as compared to the control group in which MIRB-hNPCs were injected in the absence of a static magnetic field. Fluoro-Jade C staining and immunolabeling with specific markers confirmed the viability status of MIRB-hNPCs posttransplantation. These results show that increased homing and retention of MIRB-hNPCs post-TBI by applying a static magnetic field is a promising technique to deliver cells into the CNS for treatment of neurological injuries and neurodegenerative diseases.

Cell labeling with magnetic nanoparticles: opportunity for magnetic cell imaging and cell manipulation

This tutorial describes a method of controlled cell labeling with citrate-coated ultra small superparamagnetic iron oxide nanoparticles. This method may provide basically all kinds of cells with sufficient magnetization to allow cell detection by high-resolution magnetic resonance imaging (MRI) and to enable potential magnetic manipulation. In order to efficiently exploit labeled cells, quantify the magnetic load and deliver or follow-up magnetic cells, we herein describe the main requirements that should be applied during the labeling procedure. Moreover we present some recommendations for cell detection and quantification by MRI and detail magnetic guiding on some real-case studies in vitro and in vivo.

Design of Biomimetic Vascular Grafts with Magnetic Endothelial Patterning

The development of small diameter vascular grafts with a controlled pluricellular organization is still needed for effective vascular tissue engineering. Here, we describe a technological approach combining a tubular scaffold and magnetically labeled cells to create a pluricellular and organized vascular graft, the endothelialization of which could be monitored by MRI prior to transplantation. A novel type of scaffold was developed with a tubular geometry and a porous bulk structure enabling the seeding of cells in the scaffold pores. A homogeneous distribution of human mesenchymal stem cells in the macroporous structure was obtained by seeding the freeze-dried scaffold with the cell suspension. The efficient covering of the luminal surface of the tube was then made possible thanks to the implementation of a magnetic-based patterning technique. Human endothelial cells or endothelial progenitors were magnetically labeled with iron oxide nanoparticles and successfully attracted to the 2-mm lumen where they attached and formed a continuous endothelium. The combination of imaging modalities [fluorescence imaging, histology, and 3D magnetic resonance imaging (MRI)] evidenced the integrity of the vascular construct. In particular, the observation of different cell organizations in a vascular scaffold within the range of resolution of single cells by 4.7 T MRI is reported.

Real-time assessment of ultrasound-mediated drug delivery using fibered confocal fluorescence microscopy

PURPOSE

Transport across the plasma membrane is a critical step of drug delivery for weakly permeable compounds with intracellular mode of action. The purpose of this study is to demonstrate real-time monitoring of ultrasound (US)-mediated cell-impermeable model drug uptake with fibered confocal fluorescence microscopy (FCFM).

PROCEDURES

An in vitro setup was designed to combine a mono-element US transducer, a cell chamber with a monolayer of tumor cells together with SonoVue microbubbles, and a FCFM system. The cell-impermeable intercalating dye, SYTOX Green, was used to monitor US-mediated uptake.

RESULTS

The majority of the cell population showed fluorescence signal enhancement 10 s after US onset. The mean rate constant k of signal enhancement was calculated to be 0.23 ± 0.04 min(-1).

CONCLUSIONS

Feasibility of real-time monitoring of US-mediated intracellular delivery by FCFM has been demonstrated. The method allowed quantitative assessment of model drug uptake, holding great promise for further local drug delivery studies.

Silica-coated superparamagnetic iron oxide nanoparticles targeting of EPCs in ischemic brain injury

Intravenous transplantation of endothelial progenitor cells (EPCs) reduced ischemic brain injury. However, less cell homing to damaged sites limited its functions. In present study, we labeled EPCs with silica-coated superparamagnetic iron oxide nanoparticles (SiO4@SPIONs) and applied exterior magnetic field to guide SiO4@SPIONs-labeled EPCs (SiO4@SPIONs-EPCs) to the ischemic hemisphere of the brain. We optimized SiO4@SPIONs labeling dose, which did not affect proliferation, migration and tube formation of EPCs in vitro. SiO4@SPIONs-EPCs homing was greatly increased in ischemic hemisphere with magnetic field treatment in mice underwent transient middle cerebral artery occlusion (tMCAO). Injection of SiO4@SPIONs-EPCs and followed by magnetic field treatment showed improved neurobehavioral outcomes, reduced brain atrophic volume, increased microvessel density and VEGF expression in the ischemic perifocal region compared to groups without magnetic field treatment (p < 0.05). Our results demonstrated that exterior magnetic field could guide SiO4@SPIONs-EPCs to ischemic region and enhance therapeutic effect, suggesting that magnetic-guided SiO4@SPIONs-EPCs delivery is a promising approach in cerebral ischemic therapy.

Can Magnetic Targeting of Magnetically Labeled Circulating Cells Optimize Intramyocardial Cell Retention?

Therapeutic intracavitary stem cell infusion currently suffers from poor myocardial homing. We examined whether cardiac cell retention could be enhanced by magnetic targeting of endothelial progenitor cells (EPCs) loaded with iron oxide nanoparticles. EPCs were magnetically labeled with citrate-coated iron oxide nanoparticles. Cell proliferation, migration, and CXCR4 chemokine receptor expression were assessed in different labeling conditions and no adverse effects of the magnetic label were observed. The magnetophoretic mobility of labeled EPCs was determined in vitro, with the same magnet as that subsequently used in vivo. Coronary artery occlusion was induced for 30 min in 36 rats (31 survivors), followed by 20 min of reperfusion. The rats were randomized to receive, during brief aortic cross-clamping, direct intraventricular injection of culture medium ( n = 7) or magnetically labeled EPCs ( n = 24), with ( n = 14) or without ( n = 10) subcutaneous insertion of a magnet over the chest cavity ( n = 14). The hearts were explanted 24 h later and engrafted cells were visualized by magnetic resonance imaging (MRI) of the heart at 1.5 T. Their abundance in the myocardium was also analyzed semiquantitatively by immunofluorescence, and quantitatively by real-time polymerase chain reaction (RT-PCR). Although differences in cell retention between groups failed to be statistically significant using RT-PCR quantification, due to the variability of the animal model, immunostaining showed that the average number of engrafted EPCs was significantly ten times higher with than without magnetic targeting. There was thus a consistent trend favoring the magnet-treated hearts, thereby suggesting magnetic targeting as a potentially new mean of enhancing myocardial homing of intravascularly delivered stem cells. Magnetic targeting has the potential to enhance myocardial retention of intravascularly delivered endothelial progenitor cells.

Oh the irony: Iron as a cancer cause or cure?

Iron-oxide nanoparticles facilitate cancer diagnosis through enhanced contrast, selectively enhance tumor cell death with magnetic hyperthermia, and improve drug delivery with magnetic drug targeting. One application that remains largely unexplored is using the iron-oxide nanoparticles themselves to selectively inhibit tumor growth. In this leading opinion paper, we propose that high doses of iron-oxide nanoparticles can be used as a treatment for cancer by generating an oxidative assault against cancer. This proposal may be met with resistance considering the controversy surrounding iron in the field of cancer. Iron generates reactive oxygen species through the Fenton reaction, which may both cause - or cure cancer. Additionally, high demand for iron by cancer cells leads to contradictory therapeutic approaches: iron deprivation or overdose are both potential cancer therapies.

Optical imaging and magnetic field targeting of magnetic nanoparticles in tumors

To address efficacy issues of cancer diagnosis and chemotherapy, we have developed a magnetic nanoparticle (MNP) formulation with combined drug delivery and imaging properties that can potentially be used in image-guided drug therapy. Our MNP consists of an iron-oxide magnetic core coated with oleic acid (OA) and stabilized with an amphiphilic block copolymer. Previously, we reported that our MNP formulation can provide prolonged contrast for tumor magnetic resonance imaging and can be loaded with hydrophobic anticancer agents for sustained drug delivery. In this study, we developed MNPs with optical imaging properties using new near-infrared dyes to quantitatively determine their long-term biodistribution and tumor localization with and without an external magnetic field in mice with xenograft breast tumors. MNPs localized slowly in the tumor, reaching a peak 48 h post-injection before slowly declining over the next 11 days. One hour exposure of the tumor to a magnetic field further enhanced MNP localization to tumors. Our MNPs can be developed with combined drug delivery and multimodal imaging properties to improve cancer diagnosis, provide sustained treatment, and monitor therapeutic effects in tumors over time.

Magnetic labeling, imaging and manipulation of endothelial progenitor cells using iron oxide nanoparticles

Endothelial progenitor cells (EPCs), originating from bone marrow, play a significant role in the repair of ischemic tissue and injured blood vessels. They are also involved in tumor angiogenesis. The therapeutic potential of EPCs for regenerative medicine and cancer treatment calls for new methods for monitoring and controlling cell migration. This review focuses on promising magnetic methods based on the internalization of magnetic nanoparticles by EPCs. We first describe the cellular uptake of iron oxide nanoparticles depending on their surface properties. We thus review the use of MRI for the detection of labeled cells and for noninvasive follow-up of EPCs homing in sites of endothelium regeneration. Finally, we show that remotely applied magnetic forces may enable intracellular manipulation and may optimize cell-delivery strategies for localizing cell therapy to target sites.