Recent Progress in Superparamagnetic Iron Oxide Nanoparticles

Superparamagnetic iron oxide nanoparticles(SPIONs)have immeasurable potentials in many fields such as nanobiotechnology and biomedical engineering because of their superparamagnetic properties and small particle size.This review introduces the methods for SPIONs synthesis,including co-precipitation,thermal decomposition,microemulsion and hydrothermal reaction,and surface modification of SPIONs with organometallic and inorganic metals,surface modification for targeted drug delivery,and the use of SPIONs as a contrast agent.In addition,this article also provides an overview of recent progress in SPIONs for the treatment of glioma,lung cancer and breast cancer.

Magnetic labeling of primary murine monocytes using very small superparamagnetic iron oxide nanoparticles

Due to their very small size,nanoparticles can interact with all cells in the central nervous system.One of the most promising nanoparticle subgroups are very small superparamagnetic iron oxide nanoparticles(VSOP)that are citrate coated for electrostatic stabilization.To determine their influence on murine blood-derived monocytes,which easily enter the injured central nervous system,we applied VSOP and carboxydextran-coated superparamagnetic iron oxide nanoparticles(Resovist).We assessed their impact on the viability,cytokine,and chemokine secretion,as well as iron uptake of murine blood-derived monocytes.We found that(1)the monocytes accumulated VSOP and Resovist,(2)this uptake seemed to be nanoparticle-and time-dependent,(3)the decrease of monocytes viability was treatment-related,(4)VSOP and Resovist incubation did not alter cytokine homeostasis,and(5)overall a 6-hour treatment with 0.75 mM VSOP-R1 was probably sufficient to effectively label monocytes for future experiments.Since homeostasis is not altered,it is safe to label blood-derived monocles with VSOP.VSOP labeled monocytes can be used to study injured central nervous system sites further,for example with drug-carrying VSOP.

In Vitro Targeted Magnetic Delivery and Tracking of Superparamagnetic Iron Oxide Particles Labeled Stem Cells for Articular Cartilage Defect Repair

To assess a novel cell manipulation technique of tissue engineering with respect to its ability to augment superparamagnetic iron oxide particles （SPIO） labeled mesenchymal stem cells （MSCs） density at a localized cartilage defect site in an in vitro phantom by applying magnetic force. Meanwhile, non-invasive imaging techniques were use to track SPIO-labeled MSCs by magnetic resonance imaging （MRI）. Human bone marrow MSCs were cultured and labeled with SPIO. Fresh degenerated human osteochondral fragments were obtained during total knee arthroplasty and a cartilage defect was created at the center. Then, the osteochondral fragments were attached to the sidewalls of culture flasks filled with phosphate-buffered saline （PBS） to mimic the human joint cavity. The SPIO-labeled MSCs were injected into the culture flasks in the presence of a 0.57 Tesla （T） magnetic force. Before and 90 min after cell targeting, the specimens underwent T2-weighted turbo spin-echo （SET2WI） sequence of 3.0 T MRI. MRI results were compared with histological findings. Macroscopic observation showed that SPIO-labeled MSCs were steered to the target region of cartilage defect. MRI revealed significant changes in signal intensity （P0.01）. HE staining exibited that a great number of MSCs formed a three-dimensional （3D） cell ＂sheet＂ structure at the chondral defect site. It was concluded that 0.57 T magnetic force permits spatial delivery of magnetically labeled MSCs to the target region in vitro. High-field MRI can serve as an very sensitive non-invasive technique for the visualization of SPIO-labeled MSCs.

Toxicity of superparamagnetic iron oxide nanoparticles: Research strategies and implications for nanomedicine

Superparamagnetic iron oxide nanoparticles （SPIONs） are one of the most versatile and safe nanoparticles in a wide variety of biomedical applications. In the past decades, considerable efforts have been made to investigate the potential adverse biological effects and safety issues associated with SPIONs, which is essential for the development of next-generation SPIONs and for continued progress in translational research. In this mini review, we summarize recent developments in toxicity studies on SPIONs, focusing on the relationship between the physicochemical properties of SPIONs and their induced toxic biological responses for a better toxicological understanding of SPIONs.

Comparative Study of Images with Pathology:Superparamagnetic Iron Oxide-enhanced Magnetic Resonance Image(MRI)of Splenic VX2 Tumor in Rats

Objective： To establish a rodent model of VX2 tumor of the spleen, to analyze relationship between the change of the signal intensity on superparamagnetic iron oxide enhanced magnetic resonance image （MRI） and pathologic change to evaluate the ability of superparamagnetic iron oxide enhanced MRI for detection of splenic metastases. Methods： 8 rodent models of VX2 tumor of spleen were established successfully. The images were obtained before and after administration of superparamagnetic iron oxide. T1-weighted spin-echo （SE） pulse sequence with a repetition time （TR） of 450 msec, and echo time （TE） of 12 msec （TR/TE=450/12） was used. The imaging parameters of T2-weighted SE pulse sequence were as follows： TR/TE=4000/128. Results： On plain MR scanning T1-weighted splenic VX2 tumor showed hypointensity or isointensity which approximated to the SI of splenic parenchyma. Therefore all lesions were not displayed clearly. On superparamagnetic iron oxide enhancement T2WI sequence the SI of splenic parenchyma decreased obviously with percentage of signal intensity loss （PSIL） of 55.04%, But the SI of tumor was not evidently changed with PSIL of 0.87%. Nevertheless the SNR of normal splenic parenchyma around the lesions had obvious difference （P〈0.001） comparatively. Therefore the contrast between tumor and spleen increased, and tumor displayed more clearly. Moreover the contrast-to-noise （CNR） between VX2 tumor and splenic parenchyma had an evident difference before and after admininstration of superparamagnetic iron oxide （P〈0.001）. Conclusion： On superparamagnetic iron oxide enhancement T1WI sequence the contrast of tumor-to-spleen is poor. Therefore it is not sensitive to characterize the lesions in spleen. On superparamagnetic iron oxide enhanced T2WI the contrast degree of lesions increases obviously. Consequently, superparamagnetic iron oxide -enhanced T2WI MRI scanning can improve the rate of detection and characterization for lesions of spleen.

Superparamagnetic iron oxide nanoparticles: promote neuronal regenerative capacity?

Currently,we know that neuronal outgrowth during development and regeneration requires a complex interaction of intra-and extracellular molecules such as growth factors,neurotransmitters and extracellular matrix proteins（O’Donnell et al.,2009）.Furthermore,the discovery of a broad spectrum of growth-promoting cues has led to novel concepts for thera-peutic strategies.

Superparamagnetic Iron Oxide Labeling of Spinal Cord Neural Stem Cells Genetically Modified by Nerve Growth Factor-β

This study established superparamagnetic iron oxide （SPIO）-labeled nerve growth fac-tor-β （NGF-β） gene-modified spinal cord-derived neural stem cells （NSCs）. The El4 rat embryonic spinal cord-derived NSCs were isolated and cultured. The cells of the third passage were transfected with plasmid pcDNA3-hNGFβ by using FuGENE HD transfection reagent. The expression of NGFβ was measured by immunocytochemistry and Western blotting. The positive clones were selected, allowed to proliferate and then labeled with SPIO, which was mediated by FuGENE HD transfection reagent. Prussian blue staining and transmission electron microscopy （TEM） were used to identify the SPIO particles in the cells. The distinctive markers for stem cells （nestin）, neuron （β-Ⅲ-tubulin）, oligodendrocyte （CNPase） and astrocyte （GFAP） were employed to evaluate the differentiation ability of the labeled cells. The immunocytochemistry and western blotting showed that NGF-β was expressed in spinal cord-derived NSCs. Prussian blue staining indicated that numerous blue-stained particles appeared in the cytoplasma of the labeled cells. TEM showed that SPIO particles were found in vacuolar structures of different sizes and the cytoplasma. The immunocytochemistry demonstrated that the labeled cells were nestin-positive. After differentiation, the cells expressed β-Ⅲ-tubulin, CNPase and GFAP. It was concluded that the SPIO-labeled NGF-β gene-modified spinal cord-derived NSC were successfully established, which are multipotent and capable of self-renewal.

Growth and differentiation of neural stem cells with superparamagnetic iron oxides labeling in vitro

Objective： To study the growth and differentiation of superparamagnetie iron oxides（SPIOs） labeled neural stem cells （NSCs）. Methods： After NSCs were cultured and subcuhured from newborn rat brain, they were magnetically labeled with ferumoxides （a kind of SPIOs ）. Growth, differentiation and other biology properties of the cells were investigated with immunocytochemistry, transmission electron microscopy （TEM） and Prussian blue staining. Results： Nestin positive cells were found in the culture and offspring clones. NSCs could be differentiated into positive GFAP and NF200 cells in serum culture. When NSCs incubated with ferumoxides, the iron particles were seen in intracellular as well as in offspring clones. With the increase in concentration of ferumoxides （5.6-11.2/μg/ml）, ferumoxides showed no significant difference effects on the growth and differentiation of NSCs. When the concentration of ferumoxides exceeded 22.4μg/ml ,there was significant difference（P〈0.05）. Conclusion： We successfully label NSCs with ferumoxides,it is useful for tracking of magnetic labeled NSCs in vivo with MRI.

Fluorescence detection of Europiumdoped very small superparamagnetic iron oxide nanoparticles in murine hippocampal slice cultures

In the late 1980s,superparamagnetic iron oxide nanoparticles（SPIO）moved into focus as contrast agents in magnetic resonance imaging（MRI）,due to their strong relaxivity and resulting higher resolution of images.At the time,no one anticipated their high potential in basic research or for medical diagnostic andtreatment. Since then, SPIO have been evaluated notonly as spe- cific markers for MRI, but also for cell labeling and tracking （Li et al., 2013）.

Hypoxia Enhances the Therapeutic Potential of Superparamagnetic Iron Oxide-labeled Adipose-derived Stem Cells for Myocardial Infarction

Adipose-derived stem cells（ASCs） induce therapeutic angiogenesis due to pro-angiogenic cytokines secretion. Superparamagnetic iron oxide（SPIO） nanoparticles are critical for magnetic resonance（MR） tracking of implanted cells. Hypoxia is a powerful stimulus for angiogenic activity of ASCs. In this study, we investigated whether therapeutic potency could be enhanced by implantation of hypoxia-preconditioned SPIO-labeled ASCs（SPIOASCs） into the infarcted myocardium. ASCs and SPIOASCs were cultured under 2% O_2（hypoxia） or 95% air（normoxia）. Cells were intramyocardially injected into the infarcted myocardium after 48-h culture. We found that hypoxia culture increased the m RNA expression of hypoxia-inducible factor-1 alpha（HIF-1α） and vascular endothelial growth factor（VEGF） in ASCs and SPIOASCs. The VEGF protein in the conditioned medium was significantly higher in hypoxic ASCs and SPIOASCs than in normoxic ASCs and SPIOASCs. The capillary density and left ventricular contractile function in the infarcted myocardium were significantly higher 4 weeks after implantation with hypoxic ASCs and SPIOASCs than with normoxic ASCs and SPIOASCs. Improvement in the capillary density and left ventricle function didn＇t differ between hypoxic ASCs-transplanted rats and hypoxic SPIOASCs-transplanted rats. Hypoxic culture enhanced the angiogenic efficiency of ASCs. It was concluded that implantation of hypoxic ASCs or SPIOASCs promotes therapeutic angiogenesis and cardiac function recovery in the infarcted myocardium. SPIO labeling does not impact the beneficial effect of hypoxic ASCs.

Ultra-small superparamagnetic iron oxide nanoparticles for intra-articular targeting of cartilage in early osteoarthritis

Early diagnosis of osteoarthritis(OA)is critical for effective cartilage repair.However,lack of blood vessels in articular cartilage poses a barrier to contrast agent delivery and subsequent diagnostic imaging.To address this challenge,we proposed to develop ultra-small superparamagnetic iron oxide nanoparticles(SPIONs,4 nm)that can penetrate into the matrix of articular cartilage,and further modified with the peptide ligand WYRGRL(particle size,5.9 nm),which allows SPIONs to bind to type II collagen in the cartilage matrix and increase the retention of probes.Type II collagen in the cartilage matrix is gradually lost with the progression of OA,consequently,the binding of peptide-modified ultra-small SPIONs to type II collagen in the OA cartilage matrix is less,thus presenting different magnetic resonance(MR)signals in OA group from the normal ones.By introducing the AND logical operation,damaged cartilage can be differentiated from the surrounding normal tissue on T1 and T2 AND logical map of MR images,and this was also verified in histology studies.Overall,this work provides an effective strategy for delivering nanosized imaging agents to articular cartilage,which could potentially be used to diagnosis joint-related diseases such as osteoarthritis.

In situ self-assembly of amphiphilic dextran micelles and superparamagnetic iron oxide nanoparticle-loading as magnetic resonance imaging contrast agents

Polymeric micelles have long been considered as promising nanocarrier for hydrophobic drugs and imaging probes,due to their nanoscale particle size,biocompatibility and ability to loading reasonable amount of cargoes.Herein,a facile method for dextran micelles preparation was developed and their performance as carriers of superparamagnetic iron oxide(SPIO)nanocrystals was evaluated.Amphiphilic dextran(Dex-g-OA)was synthesized via the Schiff base reactions between oxidized dextran and oleylamine,and self-assembled in situ into nano-size micelles in the reaction systems.The self-assembling behaviors of the amphiphilic dextran were identified using fluorescence resonance energy transfer technique by detection the energy transfer signal between the fluorophore pairs,Cy5 and Cy5.5.Hydrophobic SPIO nanoparticles(Fe_(3)O_(4)NPs)were successfully loaded into the dextran micelles via the in situ self-assembly process,leading to a series of Fe_(3)O_(4)NPs-loaded micelle nanocomposites(Fe_(3)O_(4)@Dex-g-OA)with good biocompatibility,superparamagnetism and strongly enhanced T_(2)relaxivity.At the magnetic field of 0.5 T,the Fe_(3)O_(4)@Dex-g-OA nanocomposite with particle size of 116.2±53.7 nm presented a higher T_(2)relaxivity of 327.9 mM_(re)^(-1)·s^(-1)·s^(−1).The prepared magnetic nanocomposites hold the promise to be used as contrast agents in magnetic resonance imaging.

Superparamagnetic iron oxide nanoparticle targeting of adipose tissue-derived stem cells in diabetes-associated erectile dysfunction

Erectile dysfunction （ED） is a major complication of diabetes, and many diabetic men with ED are refractory to common ED therapies. Adipose tissue-derived stem cells （ADSCs） have been shown to improve erectile function in diabetic animal models. However, inadequate cell homing to damaged sites has limited their efficacy. Therefore, we explored the effect of ADSCs labeled with superparamagnetic iron oxide nanoparticles （SPIONs） on improving the erectile function of streptozotocin-induced diabetic rats with an external magnetic field. We found that SPIONs effectively incorporated into ADSCs and did not exert any negative effects on stem cell properties. Magnetic targeting of ADSCs contributed to long-term cell retention in the corpus cavernosum and improved the erectile function of diabetic rats compared with ADSC injection alone. In addition, the paracrine effect of ADSCs appeared to play the major role in functional and structural recovery. Accordingly, magnetic field-guided ADSC therapy is an effective approach for diabetes-associated ED therapy.

Specific targeting of angiogenesis in lung cancer with RGD-conjugated ultrasmall superparamagnetic iron oxide particles using a 4.7T magnetic resonance scanner

Background Angiogenesis is an essential step for tumor development and metastasis.The cell adhesion molecule αvβ3 integrin plays an important role in angiogenesis and is a specific marker of tumor angiogenesis.A novel αvβ3 integrintargeted magnetic resonance （MR） imaging contrast agent utilizing Arg-Gly-Asp （RGD） and ultrasmall superparamagnetic iron oxide particles （USPIO） （referred to as RGD-USPIO） was designed and its uptake by endothelial cells was assessed both in vitro and in vivo to evaluate the angiogenic profile of lung cancer.Methods USPIO were coated with-NH3＋ and conjugated with RGD peptides.Prussian blue staining was performed to evaluate the specific uptake of RGD-USPIO by human umbilical vein endothelial cells （HUVECs）.Targeted uptake and subcellular localization of RGD-USPIO in HUVECs were confirmed by transmission electron microscopy （TEM）.The ability of RGD-USPIO to noninvasively assess αvβ3 integrin positive vessels in lung adenocarcinoma A549 tumor xenografts was evaluated with a 4.7T MR scanner.Immunohistochemistry was used to detect αvβ3 integrin expression and vessel distribution in A549 tumor xenografts.Results HUVECs internalized RGD-USPIO significantly more than plain USPIO.The uptake of RGD-USPIO by HUVECs could be competitively inhibited by addition of free RGD.A significant decrease in T2 signal intensity （SI） was observed at the periphery of A549 tumor xenografts at 30 minutes （P 〈0.05） and 2 hours （P 〈0.01） after RGD-USPIO was injected via the tail vein.Angiogenic blood vessels were mainly distributed in the periphery of tumor xenografts with positive αvβ3 integrin expression.Conclusions RGD-USPIO could specifically label αvβ3 integrin and be taken up by HUVECs.This molecular MR imaging contrast agent can specifically evaluate the angiogenic profile of lung cancer using a 4.7T MR scanner.

Efficiently tracking of stem cells in vivo using different kinds of superparamagnetic iron oxide in swine with myocardial infarction

Background Superparamagnetic iron oxide （SPIO） particles have shown much promise as a means to visualize labeled cells using molecular magnetic resonance imaging （MRI）. Micrometer-sized superparamagnetic iron oxide （MPIO）particles and nanometer-sized ultrasmall superparamagnetic iron oxide （USPIO） are two kinds of SPIO widely used for monitoring stem cells migration. Here we compare the efficiency of two kinds of SPIO during the use of stem cells to treat acute myocardial infarction （AMI）.Methods An AMI model in swine was created by 60 minutes of balloon occlusion of the left anterior descending coronary artery. Two kinds of SPIO particles were used to track after intracoronary delivered 107 magnetically labeled mesenchymal stem cells （MR-MSCs）. The distribution and migration of the MR-MSCs were assessed with the use of 3.0T MR scanner and then the results were confirmed by histological examination.Results MR-MSCs appeared as a local hypointense signal on T2 -weighted MRI and there was a gradual loss of the signal intensity after intracoronary transplantation. All of the hypointense signals in the USPIO-labeled group were found on T2 -weighted MRI, contrast to noise ratio （CNR） decreased in the MPIO-labeled group （16.07±5.85 vs. 10.96±1.34）and USPIO-labeled group （11.72±1.27 vs. 10.03±0.96） from 4 to 8 weeks after transplantation. However, the hypointense signals were not detected in MPIO-labeled group in two animals. MRI and the results were verified by histological examination.Conclusions We demonstrated that two kinds of SPIO particles in vitro have similar labeling efficiency and viability.USPIO is more suitable for labeling stem cells when they are transplanted via a coronary route.

Epidermal growth factor receptor-targeted ultra-small superparamagnetic iron oxide particles for magnetic resonance molecular imaging of lung cancer cells in vitro

Background Magnetic resonance （MR） molecular imaging can detect abnormalities associated with disease at the level of cell and molecule. The epidermal growth factor receptor （EGFR） plays an important role in the development of lung cancer. This study aimed to explore new MR molecular imaging targeting of the EGFR on lung cancer cells. Methods We attached ultra-small superparamagnetic iron oxide （USPIO） particles to cetuximab （C225） anti-human IgG using the carbodiimide method. We made the molecular MR contrast agents C225-USPIO and IgG-USPIO, the latter as a control reagent, and determined concentrations according to the Fe content. Lung cancer A549 cells were cultured and immunocytochemistry （SP） was used to detect the expression of EGFR on cells. We detected the binding rate of C225-USPIO to A549 cells with immunofluorescence staining and flow cytometry. We cultured A549 cells with C225-USPIO at a Fe concentration of 50 pg/ml and assayed the binding of C225-USPIO after 1 hour with Prussian blue staining and transmission electron microscopy （TEM）. We determined the effects on imaging of the contrast agent targeted to cells using a 4.7T MRI. We did scanning on the cells labeled with C225-USPIO, IgG-USPIO, and distilled water, respectively. The scanning sequences included axial T1WI, T2WI. Results Immunocytochemical detection of lung cancer A549 cells found them positive for EGFR expression. Immunofluorescence staining and flow cytometry after cultivation with different concentrations of C225-USPIO showed the binding rate higher than the control. Prussian blue staining and transmission electron microscopy revealed that in the C225-USPIO contrast agent group of cells the particle content of Fe in cytoplasmic vesicles or on surface was more than that in the control group. The 4.7T MR imaging （MRI） scan revealed the T2WI signal in the C225-USPIO group of cells decreased significantly more than in unlabeled cells, but there was no significant difference between the time gradients. Conclusions We successfully constructed the molecular imaging agent C225-USPIO targeting the EGFR of A549 lung cancer cells. The imaging agent showed good targeting effect and specificity, and reduced MRI T2 value significantly, thus such molecular contrast agents could provide a new way to measure EGFR levels.

Integration of PEG-conjugated gadolinium complex and superparamagnetic iron oxide nanoparticles as T_(1)-T_(2) dual-mode magnetic resonance imaging probes

The T_(1)-T_(2) dual-mode probes for magnetic resonance imaging(MRI)can non-invasively acquire comprehensive information of different tissues or generate self-complementary information of the same tissue at the same time,making MRI a more flexible imaging modality for complicated applications.In this work,three Gadolinium-diethylene-triaminepentaaceticacid(Gd-DTPA)complex conjugated superparamagnetic iron oxide(SPIO)nanoparticles with different Gd/Fe molar ratio(0.94,1.28 and 1.67)were prepared as T_(1)-T_(2) dual-mode MRI probes,named as SPIO@PEG-GdDTPA0.94,SPIO@PEGGdDTPA1.28 and SPIO@PEG-GdDTPA1.67,respectively.All SPIO@PEG-GdDTPA nanocomposites with 8 nm spherical SPIO nanocrystals showed good Gd3þchelate stability.SPIO@PEG-GdDTPA0.94 nanocomposites with lowest Gd/Fe molar ratio show no cytotoxicity to Raw 264.7 cells as compared to SPIO@PEG-GdDTPA1.28 and SPIO@PEG-GdDTPA1.67.SPIO@PEG-GdDTPA0.94 nanocomposites with r1(8.4mM^(-1)s^(-1)),r2(83.2mM^(-1)s^(-1))and relatively ideal r2/r1 ratio(9.9)were selected for T_(1)-T_(2) dual-mode MRI of blood vessels and liver tissue in vivo.Good contrast images were obtained for both cardiovascular system and liver in animal studies under a clinical 3 T scanner.Importantly,one can get high-quality contrast-enhanced blood vessel images within the first 2 h after contrast agent administration and acquire liver tissue anatomy information up to 24 h.Overall,the strategy of one shot of the dual mode MRI agent could bring numerous benefits not only for patients but also to the radiologists and clinicians,e.g.saving time,lowering side effects and collecting data of different organs sequentially.

Synthesis and application of superparamagnetic iron oxide nanoparticles in targeted therapy and imaging of cancer

Superparamagnetic iron oxide(SPIO)nanoparticles have become a popular strategy of cancer treatment and molecular imaging because of their versatile properties and biocompatibility.A variety of studies have shown the exciting potential of functionalized SPIO nanoparticles,such as surface-coated,targeted ligandconjugated,and/or drug-loaded SPIO nanoparticles,as powerful tools for targeted imaging and therapy.Moreover,the applications of SPIO nanoparticles that integrate diagnosis and therapy in SPIO nanoparticles facilitate the monitoring of therapeutic efficacy during treatment.In the present review,we primarily concentrate on the recent advancements in the field of SPIO nanoparticles in terms of synthesis,targeted therapy,and cancer imaging.

MRI tracking of human Wharton’s jelly stem cells seeded onto acellular dermal matrix labeled with superparamagnetic iron oxide nanoparticles in burn wounds

Background:In vivo cell tracking after transplantation in regenerative medicine remains an unmet challenge and limits current understanding of the wound healing mechanism through cell-based therapies.This study investigated tracking of human Wharton’s jelly stem cells(hWJSCs)seeded onto an acellular dermal matrix(ADM)and labeled with superparamagnetic iron oxide nanoparti-cles(SPIONs)by magnetic resonance imaging(MRI)in burn injury.Method:The hWJSCs were characterized and assessed for growth kinetics.A total of 30 rats were enrolled in three equal groups.Group 1 underwent scald burn injury left without treatment,the group 2 was treated by an ADM that was prepared from cosmetic surgery skin samples and the group 3 received hWJSCs labeled with SPIONs seeded onto an ADM.Tensile strength was evaluated before and after interventions,real time PCR assessed apoptosis,and Prussian blue staining,scanning electron microscopy(SEM)and MRI were used for the tracking of labeled cells.Results:The hWJSCs exhibited mesenchymal stem cell properties.Population doubling time was 40.1 hours.SPIONs did not show any toxic effect.The hWJSCs seeded onto an ADM decreased Bax and increased Bcl-2 gene expression.Internalization of SPIONs within hWJSCs was confirmed by Prussian blue staining,SEM and MRI until day 21.There was a significant difference between the Young’s moduli of normal skin and the group receiving hWJSCs seeded onto an ADM.Histological observations and SEM imaging confirmed that MRI is an accurate method to track SPION-labeled hWJSCs in vivo.Conclusions:This study showed that SPION labeling coupled with MRI can be used to further understand the fate of stem cells after transplantation in a burn model.

Bone marrow mesenchymal stem cell transplantation for treatment of spinal cord injury An in vivo magnetic resonance imaging tracking study

Non-invasive tracing in vivo can be used to observe the migration and distnbution of grafted stem cells, and can provide experimental evidence for treatment. This study utilized adenovirus-carrying enhanced green fluorescent protein （AD5/F35-eGFP） and superparamagnetic iron oxide （SPIO）-Iabeled bone marrow mesenchymal stem cells （BMSCs）. BMSCs, double-labeled by AD5/F35-eGFP and SPIO, were transplanted into rats with spinal cord injury via the subarachnoid space. MRI tracing results demonstrated that BMSCs migrated to the injured spinal cord over time （T2 hypointensity signals）. This result was verified by immunofluorescence. These results indicate that MRI can be utilized to trace in vivo the SPIO-labeled BMSCs after grafting.