Cellular Magnetic Resonance Imaging Research Articles

VCAM-1-targeted core/shell nanoparticles for selective adhesion and delivery to endothelial cells with lipopolysaccharide-induced inflammation under shear flow and cellular magnetic resonance imaging in vitro.

Multifunctional nanomaterials with unique magnetic and luminescent properties have broad potential in biological applications. Because of the overexpression of vascular cell adhesion molecule-1 (VCAM-1) receptors in inflammatory endothelial cells as compared with normal endothelial cells, an anti-VCAM-1 monoclonal antibody can be used as a targeting ligand. Herein we describe the development of multifunctional core-shell Fe3O4@SiO2 nanoparticles with the ability to target inflammatory endothelial cells via VCAM-1, magnetism, and fluorescence imaging, with efficient magnetic resonance imaging contrast characteristics. Superparamagnetic iron oxide and fluorescein isothiocyanate (FITC) were loaded successfully inside the nanoparticle core and the silica shell, respectively, creating VCAM-1-targeted Fe3O4@SiO2(FITC) nanoparticles that were characterized by scanning electron microscopy, transmission electron microscopy, fluorescence spectrometry, zeta potential assay, and fluorescence microscopy. The VCAM-1-targeted Fe3O4@SiO2(FITC) nanoparticles typically had a diameter of 355 ± 37 nm, showed superparamagnetic behavior at room temperature, and cumulative and targeted adhesion to an inflammatory subline of human umbilical vein endothelial cells (HUVEC-CS) activated by lipopolysaccharide. Further, our data show that adhesion of VCAM-1-targeted Fe3O4@SiO2(FITC) nanoparticles to inflammatory HUVEC-CS depended on both shear stress and duration of exposure to stress. Analysis of internalization into HUVEC-CS showed that the efficiency of delivery of VCAM-1-targeted Fe3O4@SiO2(FITC) nanoparticles was also significantly greater than that of nontargeted Fe3O4@SiO2(FITC)-NH2 nanoparticles. Magnetic resonance images showed that the superparamagnetic iron oxide cores of the VCAM-1-targeted Fe3O4@SiO2(FITC) nanoparticles could also act as a contrast agent for magnetic resonance imaging. Taken together, the cumulative adhesion and uptake potential of these VCAM-1-targeted Fe3O4@SiO2(FITC) nanoparticles targeted to inflammatory endothelial cells could be used in the transfer of therapeutic drugs/genes into these cells or for diagnosis of vascular disease at the molecular and cellular levels in the future.

Superparamagnetic Iron Oxide Nanoparticles as MRI contrast agents for Non-invasive Stem Cell Labeling and Tracking

Stem cells hold great promise for the treatment of multiple human diseases and disorders. Tracking and monitoring of stem cells in vivo after transplantation can supply important information for determining the efficacy of stem cell therapy. Magnetic resonance imaging (MRI) combined with contrast agents is believed to be the most effective and safest non-invasive technique for stem cell tracking in living bodies. Commercial superparamagnetic iron oxide nanoparticles (SPIONs) in the aid of transfection agents (TAs) have been applied to labeling stem cells. However, owing to the potential toxicity of TAs, more attentions have been paid to develop novel SPIONs with specific surface coating or functional moieties which facilitate effective cell internalization in the absence of TAs. This review aims to summarize the recent progress in the design and preparation of SPIONs as cellular MRI probes, to discuss their applications and current problems facing in stem cell labeling and tracking, and to offer perspectives and solutions for the future development of SPIONs in this field.

Tracking Tumor Cells in Lymphatics in a Mice Xenograft Model by Magnetic Resonance Imaging

To enrich our understanding of the mechanism of tumor lymphatic metastasis, we developed a model system for tracking metastatic tumor cells in the lymphatic system with cellular magnetic resonance imaging (MRI) in live mice to observe the interaction between tumor cells and the lymphatic system. Nude mice were inoculated subcutaneously with superparamagnetic iron oxide (SPIO)-labeled and unlabeled LOVO cells in the foot pad, groin, or axillary area. Serial 7 T MRI of the tumors and surrounding regions was performed in the following 2 weeks. After imaging, tumor tissues and regional lymph nodes were collected and subjected to immunohistologic analysis. T₂/T₂*-weighted MRIs showed the primary tumor growth and the draining lymphatic architecture, as well as the SPIO-labeled tumor cells metastasized into the regional lymph node at 8 days. MRIs also revealed information on sentinel lymph node mapping with high-resolution anatomic information. Histologic findings confirmed the in vivo MRI results and revealed lymphangiogenesis, angiogenesis, infiltration of macrophages, and expression of vascular endothelial growth factor C in tumor and draining lymph nodes as well. This technology provides a powerful tool for tracking SPIO-labeled cancer cells in the lymphatics by cellular MRI. There was a close relationship between tumor lymphatic metastasis and lymphangiogenesis.

Multifunctional nanoparticles of Fe3O4@SiO2(FITC)/PAH conjugated the recombinant plasmid of pIRSE2-EGFP/VEGF165 with dual functions for gene delivery and cellular imaging

Objectives: Technologies to increase tissue vascularity are critically important to the fields of tissue engineering and cardiovascular medicine. Angiogenic factors, like VEGF, have been widely investigated to induce vascular endothelial cell proliferation and angiogenesis for establishing a vascular network. However, effective transport of VEGF gene to target cells with minimal side effects remains a challenge despite the use of unique viral and non-viral delivery approaches.Methods: This study presents a novel gene delivery system of fluorescein isothiocyanate (FITC) doped and poly(allylamine hydrochloride) (PAH) grafted Fe3O4@SiO2 nanoparticles, which allows efficient loading of pVEGF to form Fe3O4@SiO2(FITC)/PAH/pVEGF nanocomplexes for VEGF gene delivery and cellular imaging.Results: The nanocomplexes maintain their superparamagnetic property in the silica composites at room temperature, reaching a saturation magnetization value of 5.19 emu/g of material, and no appreciable change in magnetism even after PAH modification. The quantitative analysis of cellular internalization into the living human umbilical vein endothelial cells (HUVECs) demonstrated that the Fe3O4@SiO2(FITC)/PAH/pVEGF nanocomplexes could be entirely internalized by HUVECs, and exhibit high VEGF gene expression and an innocuous toxic profile. The magnetic resonance (MR) images showed that the superparamagnetic iron oxide core of Fe3O4@SiO2(FITC)/PAH/pVEGF nanocomplexes could also act as a contrast agent for MR imaging. This property provides a benefit for monitoring gene delivery.Conclusion: These data highlight multifunctional Fe3O4@SiO2(FITC)/PAH/pVEGF nanocomplexes as an attractive platform for gene delivery of angiogenesis, and also making it a potential candidate of nanoprobes for cellular fluorescent imaging or MR imaging.

Concurrent Dual Contrast for Cellular Magnetic Resonance Imaging Using Gadolinium Oxide and Iron Oxide Nanoparticles

Rationale and Objectives. Concurrent visualization of differential targets in cellular and molecular imaging is valuable for resolving processes spatially and temporally, as in monitoring different cell subtypes. The purpose of this study was to demonstrate concurrent, dual (positive and negative) contrast visualization on magnetic resonance imaging (MRI) of two colocalized cell populations labeled with Gadolinium “Gd” oxide and iron “Fe” oxide nanoparticles. Materials and Methods. Human aortic endothelial cells (EC) and smooth muscle cells (SMC) were labeled with various concentrations of Gd oxide and Fe oxide, respectively. MRI on single- or mixed-cell samples was performed at 7 tesla. Proper cell phenotype expressions, cell uptake of contrast agents, and the effect of labeling on cell viability and proliferation were also determined. Results. Both contrast agents were efficiently taken up by cells, with viability and proliferation largely unaffected. On MRI, the positive contrast associated with Gd oxide-labeled EC and negative contrast associated with Fe oxide-labeled SMC discriminated the presence of each cell type, whether it existed alone or colocalized in a mixed-cell sample. Conclusion. It is feasible to use Gd oxide and Fe oxide for dual contrast and concurrent discrimination of two colocalized cell populations on MRI at 7 tesla.

Magnetic resonance chemical exchange saturation transfer imaging and nanotechnology

Chemical exchange saturation transfer (CEST) agents and paramagnetic CEST (PARACEST) agents display bound water signals that exchange protons with the bulk water. CEST magnetic resonance imaging (MRI) relies on exchangeable protons that resonate at a chemical shift that is distinguishable from the bulk water signal. In some cases, paramagnetic chelates are utilized to shift the bound water frequency further away from the bulk water. Radiofrequency prepulses applied at the appropriate frequency can saturate the exchangeable protons, which transfer into the bulk water pool and lead to reduced equilibrium magnetization. Therefore, CEST and PARACEST agents allow the image contrast to be switched 'on' and 'off' by simply changing the pulse sequence parameters. One of the main limitations with this approach is the inherent insensitivity of MRI to CEST and PARACEST agents. Nanoscale carriers have been developed to improve the limit of detection for these agents, demonstrating the feasibility of in vivo molecular or cellular MRI based on CEST or PARACEST contrast. These carriers have been based on a number of different nanoparticle constructs, such as liposomes, dendrimers, polymers, adenovirus particles, and perfluorocarbon nanoparticles. The unique MRI properties of CEST and PARACEST nanoparticle systems have spawned research into an array of potential medical applications.

Tracking T-cells in vivo with a new nano-sized MRI contrast agent

Non-invasive in vivo tracking of T-cells by magnetic resonance imaging (MRI) can lead to a better understanding of many pathophysiological situations, including AIDS, cancer, diabetes, graft rejection. However, an efficient MRI contrast agent and a reliable technique to track non-phagocytic T-cells are needed. We report a novel superparamagnetic nano-sized iron-oxide particle, IOPC-NH2 series particles, coated with polyethylene glycol (PEG), with high transverse relaxivity (250 s−1 mM−1), thus useful for MRI studies. IOPC-NH2 particles are the first reported magnetic particles that can label rat and human T-cells with over 90% efficiency, without using transfection agents, HIV-1 transactivator peptide, or electroporation. IOPC-NH2 particles do not cause any measurable effects on T-cell properties. Infiltration of IOPC-NH2−labeled T-cells can be detected in a rat model of heart-lung transplantation by in vivo MRI. IOPC-NH2 is potentially valuable contrast agents for labeling a variety of cells for basic and clinical cellular MRI studies, e.g., cellular therapy. From the Clinical EditorIn this study, a novel PEG coated superparamagnetic nano-sized iron-oxide particle was investigated as a T-cell labeling agent for MRI studies. The reported particles can label T-cells with over 90% efficiency, without using transfection agents, HIV-1 transactivator peptide, or electroporation, therefore may enable more convenient preclinical call labeling studies.

Human Aortic Endothelial Cell Labeling with Positive Contrast Gadolinium Oxide Nanoparticles for Cellular Magnetic Resonance Imaging at 7 Tesla

Positive T₁ contrast using gadolinium (Gd) contrast agents can potentially improve detection of labeled cells on magnetic resonance imaging (MRI). Recently, gadolinium oxide (Gd₂O₃) nanoparticles have shown promise as a sensitive T₁ agent for cell labeling at clinical field strengths compared to conventional Gd chelates. The objective of this study was to investigate Gado CELLTrack, a commercially available Gd₂O₃ nanoparticle, for cell labeling and MRI at 7 T. Relaxivity measurements yielded r1 = 4.7 s⁻¹ mM⁻¹ and r₂/r₁ = 6.2. Human aortic endothelial cells were labeled with Gd₂O₃ at various concentrations and underwent MRI from 1 to 7 days postlabeling. The magnetic resonance relaxation times T₁ and T₂ of labeled cell pellets were measured. Cellular contrast agent uptake was quantified by inductively coupled plasma-atomic emission spectroscopy, which showed very high uptake compared to conventional Gd compounds. MRI demonstrated significant positive T₁ contrast and stable labeling on cells. Enhancement was optimal at low Gd concentrations, attained in the 0.02 to 0.1 mM incubation concentration range (corresponding cell uptake was 7.26 to 34.1 pg Gd/cell). Cell viability and proliferation were unaffected at the concentrations tested and up to at least 3 days postlabeling. Gd₂O₃ is a promising sensitive and stable positive contrast agent for cellular MRI at 7 T.

Water-dispersible multiwalled carbon nanotube/iron oxide hybrids as contrast agents for cellular magnetic resonance imaging

Novel magnetic resonance imaging (MRI) contrast agents composed of multiwalled carbon nanotubes decorated with magnetic iron oxide nanoparticles were explored. They were functionalized with multilayer polyelectrolytes through layer-by-layer assembling and were shown to be hydrophilic, biocompatible, and have a high MRI contrast. A targeted ligand folic acid was chemically bonded to the functionalized nanotubes for specific targeting and imaging of cancer cells in MRI. The results demonstrate that the material can be used as ideal targeted imaging agents and is sufficient to obtain strong MRI contrast.

Enhanced cellular uptake and long-term retention of chitosan-modified iron-oxide nanoparticles for MRI-based cell tracking

Tracking cells after therapeutic transplantation is imperative for evaluation of implanted cell fate and function. In this study, ultrasmall superparamagnetic iron oxide nanoparticles (USPIO NPs) were surface functionalized with water-soluble chitosan, a cationic polysaccharide that mediates enhanced endocytic uptake, endosomal escape into the cytosol, and subsequent long-term retention of nanoparticles. NP surface and chitosan were independently fluorescently labeled. Our NPs enable NP trafficking studies and determination of fate beyond uptake by fluorescence microscopy as well as tracking of labeled cells as localized regions of hypointensity in T2*-weighted magnetic resonance imaging (MRI) images. Adult rat neural stem cells (NSCs) were labeled with NPs, and assessment of NSC proliferation rates and differentiation potential revealed no significant differences between labeled and unlabeled NSCs. Significantly enhanced uptake of chitosan NPs in comparison to native NPs was confirmed by transmission electron microscopy, nuclear magnetic resonance (NMR) spectroscopy and in vitro cellular MRI at 11.7 Tesla. While only negligible fractions of native NPs enter cells, chitosan NPs appear within membranous vesicles within 2 hours of exposure. Additionally, chitosan-functionalized NPs escaped from membrane-bound vesicles within days, circumventing NP endo-lysosomal trafficking and exocytosis and hence enabling long-term tracking of labeled cells. Finally, our labeling strategy does not contain any NSC-specific reagents. To demonstrate general applicability across a variety of primary and immortalized cell types, embryonic mouse NSCs, mouse embryonic stem cells, HEK 293 kidney cells, and HeLa cervical cancer cells were additionally exposed to chitosan-USPIO NPs and exhibited similarly efficient loading as verified by NMR relaxometry. Our efficient and versatile labeling technology can support cell tracking with close to single cell resolution by MRI in vitro, for example, in complex tissue models not optically accessible by confocal or multi-photon fluorescence microscopy, and potentially in vivo, for example, in animal models of human disease or injury.

Cellular MRI as a suitable, sensitive non-invasive modality for correlating in vivo migratory efficiencies of different dendritic cell populations with subsequent immunological outcomes

The clinical application of dendritic cells (DC) as adjuvants in immunotherapies such as the cell-based cancer vaccine continues to gain interest. The overall efficacy of this emerging immunotherapy, however, remains low. Studies suggest the stage of maturation and activation of ex vivo-prepared DC immediately prior to patient administration is critical to subsequent DC migration in vivo, which ultimately affects overall vaccine efficacy. While it is possible to generate mature and activated DC ex vivo using various stimulatory cocktails, in the case of cancer patients, the qualitative and quantitative assessment of which DC stimulatory cocktail works most effectively to enhance subsequent DC migration in vivo is difficult. Thus, a non-invasive imaging modality capable of monitoring the real-time migration of DC in long-term studies is required. In this paper, we address whether cellular magnetic resonance imaging (MRI) is sufficiently sensitive to quantitatively detect differences in the migratory abilities of two different DC preparations: untreated (resting) versus ex vivo matured in a mouse model. In order to distinguish our ex vivo-generated DC of interest from surrounding tissues in magnetic resonance (MR) images, DC were labeled in vitro with the superparamagnetic iron oxide (SPIO) nanoparticle FeREX®. Characterization of DC phenotype and function following addition of a cytokine maturation cocktail and the toll-like receptor ligand CpG, both in the presence and in the absence of SPIO, were also carried out. Conventional histological techniques were used to verify the quantitative data obtained from MR images. This study provides important information relevant to tracking the in vivo migration of ex vivo-prepared and stimulated DC.

RADIOFREQUENCY AND MICROWAVE RADIATION HEALTH EFFECTS AND OCCUPATIONAL EXPOSURE

In the recent years, there have been considerable discussion and concern about the possible hazards of RF/MW radiation. More recently, the growth and development in personal mobile communications have focused attention on the frequencies associated with this technology. A number of studies have examined the health effects of RF/MW electromagnetic fields (EMFs), originating from occupational exposure, hobbies, or residence near the radio or television transmitters. Particularly controversial are the biophysical mechanisms by which these RF fields may affect biological systems. General health effects reviews explore possible carcinogenic, reproductive and neurological effects. Health effects by exposure source have been observed in radar traffic devices, wireless communications with cellular phones, radio transmission, and magnetic resonance imaging (MRI). Several epidemiological surveys have suggested associations with non-specific complaints such as headache, tiredness, sleep disturbance, loss of memory, and dizziness. These findings, which echo reports of illness associated with other types of radiofrequency (RF) radiation, relate not only to the use of mobile phones, but also to residence near the mobile phone base stations and other settings involving occupational exposure. The biological effects suggest that some precautions are necessary, and preventive approaches are highly recommended. Further researches are required to give more information about the effects of microwave radiation on our health, especially in occupational setting and professionally exposed workers.

Surface Modification of Gadolinium Oxide Thin Films and Nanoparticles using Poly(ethylene glycol)-Phosphate

The performance of nanomaterials for biomedical applications is highly dependent on the nature and the quality of surface coatings. In particular, the development of functionalized nanoparticles for magnetic resonance imaging (MRI) requires the grafting of hydrophilic, nonimmunogenic, and biocompatible polymers such as poly(ethylene glycol) (PEG). Attached at the surface of nanoparticles, this polymer enhances the steric repulsion and therefore the stability of the colloids. In this study, phosphate molecules were used as an alternative to silanes or carboxylic acids, to graft PEG at the surface of ultrasmall gadolinium oxide nanoparticles (US-Gd(2)O(3), 2-3 nm diameter). This emerging, high-sensitivity "positive" contrast agent is used for signal enhancement in T(1)-weighted molecular and cellular MRI. Comparative grafting assays were performed on Gd(2)O(3) thin films, which demonstrated the strong reaction of phosphate with Gd(2)O(3) compared to silane and carboxyl groups. Therefore, PEG-phosphate was preferentially used to coat US-Gd(2)O(3) nanoparticles. The grafting of this polymer on the particles was confirmed by XPS and FTIR. These analyses also demonstrated the strong attachment of PEG-phosphate at the surface of Gd(2)O(3), forming a protective layer on the nanoparticles. The stability in aqueous solution, the relaxometric properties, and the MRI signal of PEG-phosphate-covered Gd(2)O(3) particles were also better than those from non-PEGylated nanoparticles. As a result, reacting PEG-phosphate with Gd(2)O(3) particles is a promising, rapid, one-step procedure to PEGylate US-Gd(2)O(3) nanoparticles, an emerging "positive" contrast agent for preclinical molecular and cellular applications.

Abstract 15448: Blood Monocyte Recruitment in Microvascular Obstruction and Intramyocardial Hemorrhage: New Insights from Fluorine-19 Cellular Magnetic Resonance Imaging in Experimental Reperfused Myocardial Infarction

Yuxiang Ye, 2011 Finalist and Presenting Author

Iron Oxide Nanoparticle-Induced Epidermal Growth Factor Receptor Expression in Human Stem Cells for Tumor Therapy

Superparamagnetic iron oxide (SPIO) nanoparticles show promise as labels for cellular magnetic resonance imaging (MRI) in the application of stem cell-based therapy. However, the unaddressed concerns about the impact of SPIO nanoparticles on stem cell attributes make the feasibility of SPIO labeling uncertain. Here, we show that the labeling of human mesenchymal stem cells (hMSCs) with ferucarbotran can induce epidermal growth factor receptor (EGFR) overexpression. Labeled hMSCs with their overexpressed EGFR were attracted by tumorous EGF and more effectively migrated toward tumor than unlabeled cells, resulting in more potent intrinsic antitumor activity. Moreover, the captured binding of tumorous EGF by overexpressed EGFR of labeled hMSCs blocked EGF/EGFR signaling-derived tumor growth, tumorous angiogenesis, and tumorous VEGF expression also responsible for tumor progression and development. Our results show that the impact of SPIO nanoparticles on stem cell attributes is not necessarily harmful but can be cleverly used to be beneficial to stem cell-based therapy.

Cellular magnetic resonance imaging of monocyte-derived dendritic cell migration from healthy donors and cancer patients as assessed in a scid mouse model

BACKGROUND AIMS. The use of dendritic cells (DC) as an adjuvant in cell-based immunotherapeutic cancer vaccines is a growing field of interest. A reliable and non-invasive method to track the fate of autologous DC following their administration to patients is required in order to confirm that clinically sufficient numbers are reaching the lymph node (LN). We demonstrate that an immunocompromised mouse model can be used to conduct translational studies employing cellular magnetic resonance imaging (MRI). Such studies can provide clinically relevant information regarding the migration potential of clinical-grade DC used in cancer immunotherapies. METHODS. Human monocyte-derived dendritic cells (mo-DC) were generated from negatively selected monocytes obtained from either healthy donors or cancer patients. DC were labeled with superparamagnetic iron oxide (SPIO) nanoparticles in order to track them in vivo in a CB17scid mouse model using cellular MRI. SPIO did not have any adverse effects on DC phenotype or function, independent of donor type. Cellular MRI readily detected migration of SPIO-loaded DC in CB17scid mice. No differences in migration were observed between DC obtained from healthy donors and those obtained from donors undergoing autologous stem cell transplant for cancer therapy. CONCLUSIONS. Cellular MRI provided semi-quantitative image data that corresponded with data obtained by digital morphometry, validating cellular MRI's potential to assess DC migration in DC-based cancer immunotherapy clinical trials.

Composites of Aminodextran-Coated Fe3O4 Nanoparticles and Graphene Oxide for Cellular Magnetic Resonance Imaging

Formation of composites of dextran-coated Fe(3)O(4) nanoparticles (NPs) and graphene oxide (Fe(3)O(4)-GO) and their application as T(2)-weighted contrast agent for efficient cellular magnetic resonance imaging (MRI) are reported. Aminodextran (AMD) was first synthesized by coupling reaction of carboxymethyldextran with butanediamine, which was then chemically conjugated to meso-2,3-dimercaptosuccinnic acid-modified Fe(3)O(4) NPs. Next, the AMD-coated Fe(3)O(4) NPs were anchored onto GO sheets via formation of amide bond in the presence of 1-ethyl-3-(3-dimethyaminopropyl) carbodiimide (EDC). It is found that the Fe(3)O(4)-GO composites possess good physiological stability and low cytotoxicity. Prussian Blue staining analysis indicates that the Fe(3)O(4)-GO nanocomposites can be internalized efficiently by HeLa cells, depending on the concentration of the composites incubated with the cells. Furthermore, compared with the isolated Fe(3)O(4) NPs, the Fe(3)O(4)-GO composites show significantly enhanced cellular MRI, being capable of detecting cells at the iron concentration of 5 μg mL(-1) with cell density of 2 × 10(5) cells mL(-1), and at the iron concentration of 20 μg mL(-1) with cell density of 1000 cells mL(-1).

Determining the fate of seeded cells in venous tissue‐engineered vascular grafts using serial MRI

A major limitation of tissue engineering research is the lack of noninvasive monitoring techniques for observations of dynamic changes in single tissue-engineered constructs. We use cellular magnetic resonance imaging (MRI) to track the fate of cells seeded onto functional tissue-engineered vascular grafts (TEVGs) through serial imaging. After in vitro optimization, murine macrophages were labeled with ultrasmall superparamagnetic iron oxide (USPIO) nanoparticles and seeded onto scaffolds that were surgically implanted as inferior vena cava interposition grafts in SCID/bg mice. Serial MRI showed the transverse relaxation times (T(2)) were significantly lower immediately following implantation of USPIO-labeled scaffolds (T(2) = 44 ± 6.8 vs. 71 ± 10.2 ms) but increased rapidly at 2 h to values identical to control implants seeded with unlabeled macrophages (T(2) = 63 ± 12 vs. 63 ± 14 ms). This strongly indicates the rapid loss of seeded cells from the scaffolds, a finding verified using Prussian blue staining for iron containing macrophages on explanted TEVGs. Our results support a novel paradigm where seeded cells are rapidly lost from implanted scaffolds instead of developing into cells of the neovessel, as traditionally thought. Our findings confirm and validate this paradigm shift while demonstrating the first successful application of noninvasive MRI for serial study of cellular-level processes in tissue engineering.

Efficient In Vitro Labeling of Human Prostate Cancer Cells with Superparamagnetic Iron Oxide Nanoparticles

The purpose of this study was to investigate the feasibility and optimization of protocols using superparamagnetic iron oxide (SPIO) nanoparticles to label human prostate cancer cell lines PC3 in vitro. The PC3 cells were labeled with different concentrations (28-252 μg Fe/mL) of SPIO and increasing incubation time (6-24 hours), in the presence or absence of a transfection agent poly-l-lysine (PLL). The cell labeling efficiency was analyzed by Prussian blue stain method. The cellular viability was evaluated using trypan blue dye exclusion test. The signal intensity change of the labeled cells was assessed with magnetic resonance imaging (MRI). The results demonstrated that the iron oxide uptake by PC3 cells was dependent on dose and time. The PLL significantly increased the iron load of cells (p<0.01). A final concentration of SPIO nanoparticles of 42-126 μg/mL with 12-24 hours incubation times could be sufficient to label PC3 cells for cellular MRI without impairment of cell viability. This technology may allow for further study into the mechanisms underlying prostate cancer progression as well as permit the real-time imaging of the effectiveness of cancer therapies in vivo.

Labelling dendritic cells with SPIO has implications for their subsequent in vivo migration as assessed with cellular MRI

An optimized non-invasive imaging modality capable of tracking and quantifying in vivo DC migration in patients would provide clinicians with valuable information regarding therapeutic DC-based vaccine outcomes. Superparamagnetic iron oxide (SPIO) nanoparticles were used to label bone marrow-derived DC. In vivo DC migration was tracked and quantified non-invasively using cellular magnetic resonance imaging (MRI) in a mouse model. Labelling DC with SPIO reflects the kinetics of DC migration in vivo but appears to reduce overall DC migration, in part due to nanoparticle size. Magnetic separation of SPIO-labelled (SPIO(+)) DC from unlabelled (SPIO(-)) DC prior to injection improves SPIO(+) DC migration to the lymph node. Corresponding MR image data better correlate with the presence of DC in vivo; an improved immunological response is also seen. Cellular MRI is a viable, non-invasive imaging tool that can routinely track DC migration in vivo. Consideration should be given to optimizing MRI contrast agent-labelling of clinical-grade DC in order to accurately correlate DC fate to immunological outcomes in patients.