Current status of superparamagnetic iron oxide contrast agents for liver magnetic resonance imaging

Five types of superparamagnetic iron oxide （SPIO）,i.e. Ferumoxides （Feridex？ Ⅳ, Berlex Laboratories）,Fe r u c a r b o t ra n （ Re s ov i s t？, B aye r H e a l t h c a re ） ,Ferumoxtran-10 （AMI-227 or Code-7227, Combidex？, AMAG Pharma; Sinerem？, Guerbet）, NC100150（Clariscan？, Nycomed,） and （VSOP C184, Ferropharm）have been designed and clinically tested as magneticresonance contrast agents. However, until nowResovist？ is current available in only a few countries.The other four agents have been stopped for furtherdevelopment or withdrawn from the market. AnotherSPIO agent Ferumoxytol （Feraheme） is approved forthe treatment of iron deficiency in adult chronic kidneydisease patients. Ferumoxytol is comprised of ironoxide particles surrounded by a carbohydrate coat, andit is being explored as a potential imaging approach forevaluating lymph nodes and certain liver tumors.

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.

Development and in vitro study of a bi-specific magnetic resonance imaging molecular probe for hepatocellular carcinoma

BACKGROUND Hepatocellular carcinoma(HCC)ranks second in terms of cancer mortality worldwide.Molecular magnetic resonance imaging(MRI)targeting HCC biomarkers such as alpha-fetoprotein(AFP)or glypican-3(GPC3)offers new strategies to enhance specificity and help early diagnosis of HCC.However,the existing iron oxide nanoparticle-based MR molecular probes singly target AFP or GPC3,which may hinder their efficiency to detect heterogeneous micro malignant HCC tumors<1 cm(MHCC).We hypothesized that the strategy of double antibody-conjugated iron oxide nanoparticles which simultaneously target AFP and GPC3 antigens may potentially be used to overcome the tumor heterogeneity and enhance the detection rate for MRI-based MHCC diagnosis.AIM To synthesize an AFP/GPC3 double antibody-labeled iron oxide MRI molecular probe and to assess its impact on MRI specificity and sensitivity at the cellular level.METHODS A double antigen-targeted MRI probe for MHCC anti-AFP-USPIO-anti-GPC3(UAG)was developed by simultaneously conjugating AFP andGPC3 antibodies to a 5 nm ultra-small superparamagnetic iron oxide nanoparticle(USPIO).At the same time,the singly labeled probes of anti-AFP-USPIO(UA)and anti-GPC3-USPIO(UG)and non-targeted USPIO(U)were also prepared for comparison.The physical characterization including morphology(transmission electron microscopy),hydrodynamic size,and zeta potential(dynamic light scattering)was conducted for each of the probes.The antigen targeting and MRI ability for these four kinds of USPIO probes were studied in the GPC3-expressing murine hepatoma cell line Hepa1-6/GPC3.First,AFP and GPC3 antigen expression in Hepa1-6/GPC3 cells was confirmed by flow cytometry and immunocytochemistry.Then,the cellular uptake of USPIO probes was investigated by Prussian blue staining assay and in vitro MRI(T2-weighted and T2-map)with a 3.0 Tesla clinical MR scanner.RESULTS Our data showed that the double antibody-conjugated probe UAG had the best specificity in targeting Hepa1-6/GPC3 cells expressing AFP and GPC3 antigens compared with single antibody-conjugated and unconjugated USPIO probes.The iron Prussian blue staining and quantitative T2-map MRI analysis showed that,compared with UA,UG,and U,the uptake of double antigen-targeted UAG probe demonstrated a 23.3%(vs UA),15.4%(vs UG),and 57.3%(vs U)increased Prussian stained cell percentage and a 14.93%(vs UA),9.38%(vs UG),and 15.3%(vs U)reduction of T2 relaxation time,respectively.Such bi-specific probe might have the potential to overcome tumor heterogeneity.Meanwhile,the coupling of two antibodies did not influence the magnetic performance of USPIO,and the relatively small hydrodynamic size(59.60±1.87 nm)of double antibodyconjugated USPIO probe makes it a viable candidate for use in MHCC MRI in vivo,as they are slowly phagocytosed by macrophages.CONCLUSION The bi-specific probe presents enhanced targeting efficiency and MRI sensitivity to HCC cells than singly-or non-targeted USPIO,paving the way for in vivo translation to further evaluate its clinical potential.

Migration of Resovist-labeled neural stem cells towards focal rat cerebral ischemic regions as determined by in vivo tracking and magnetic resonance imaging

BACKGROUND： Resovist, a superparamagnetic iron oxide, can be used to label neural stem cells （NSCs）. Magnetic resonance tracking of superparamagnetic iron oxide-labeled NSCs is a non-invasive technique to track transplanted NSCs following focal cerebral ischemia. OBJECTIVE： To observe survival and migration of transplanted NSCs in a rat model of focal ischemia/repeffusion using magnetic resonance imaging （MRI）. DESIGN, TIME AND SETTING： An in vitro, in vivo, tracking study was performed at the Basic Laboratory of Harbin Medical University and the Room of MRI, Second Affiliated Hospital of Harbin Medical University, China from December 2006 to December 2009. MATERIALS： Resovist （Schering, Germany） and Achieva 1.5TMR imaging system （Philips, Amsterdam, the Netherlands） were utilized in the present study. METHODS： NSCs were harvested from brain tissues of neonatal Sprague Dawley rats and were labeled with Resovist （11.2μg/mL and 5 ×10^5 cells/mL）. A total of 15 adult, Sprague Dawley rats were randomly assigned to model （n = 9） and control （n = 6） groups. All rats were utilized to establish models of middle cerebral artery occlusion. Rats in the model group were subjected to Resovist-labeled NSCs transplantation by injection of cell suspension into both ventricles （5μL/ ventricle）. Rats in the control group were treated with an equal volume of physiological saline. MAIN OUTCOME MEASURES： Immunocytochemistry, transmission electron microscopy, and Prussian blue staining were employed to observe whether cells phagocytized iron particles. In addition, 3-（4, 5-dimethylthiazol-2-yl）-2, 5-diphenyltetrazolium bromide assay was used to measure viability and differentiation of NSCs labeled by various concentrations of Resovist. MRI was used to trace survival and migration of Resovist-labeled NSCs. RESULTS： Following Resovist and NSCs co-incubation, Prussian blue staining revealed iron particles in cells. In addition, staining was observed in daughter cells following cell division under transmission electron microscopy. A significant difference in viability and differentiation of NSCs in vitro labeled by various Resovist concentrations （2.8-11.2 μg/mL） was not detected （P 〉 0.05）. Resovist （〉 22.4 μg/mL） decreased cell viability and differentiation （P 〈 0.05）./n vivo MRI of Resovist-labeled NSCs （11.2 μg/mL） revealed low signals. However, cells migrated towards the ischemic focus over time. CONCLUSION： Resovist, a magnetic probe, successfully labeled NSCs. MRI was successfully used to trace magnetic-labeled NSCs in vivo and allowed observation of cell survival and migration following transplantation.

Magnetic Resonance Imaging of Transplanted Neural Stem Cells in Parkinson Disease Rats

Summary： In this study we implanted magnetically labeled neural stem cells （NSCs） in PD rats and then monitored their survival and migration in the host brain by magnetic resonance imaging （MRI）. The mesencephalic NSCs were obtained from the brain of SD rats. Superparamagnetic iron oxide （SPIO） was transferred to NSCs by Lipofectamine transfection. Eighteen PD lesioned rats were selected for transplantation by evaluation of their rotational behavior in response to amphetamine and randomly assigned to 3 groups, i.e., sham group, PBS group and NSCs transplanted group, with 6 rats in each group. MR scanning was performed at 1, 2, 4, 6, 8 and 10 week（s） following transplantation. At the meantime, rotational behavior was assessed in each group. Our results showed that SPIO particles were clearly visible with Prissian blue staining in neurospheres and cells derived from NSCs. The rotational behavior of the NSCs transplanted group was remarkably improved compared with that of sham group and PBS group （P〈0.05）. In vivo MR tracking of NSCs showed that SPIO labeling led to a strong susceptibility change of signal 1 week after transplantation on T2 weighted images. And a large circular hypointense signal appeared in the transplanted area on T2＊ gradient echo images Ten weeks following transplantation, the hypointense signal on T2 weighted and T2＊ gradient echo images was still displayed. It is concluded that SPIO particles could label NSCs effectively, and MRI detection of SPIO labeled cells is a promising method and novel approach to analyzing the NSCs following transplantation in the treatment of PD.

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.

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.

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.

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.

Self-assembled superparamagnetic nanoparticles as MRI contrast agents — A review

Recent progress of the preparation and applications of superparamagnetic iron oxide（SPIO） clusters as magnetic resonance imaging（MRI） probes is reviewed with regard to their applications in labeling and tracking cells in vivo, in diagnosis of cardiovascular diseases and tumors, and in drug delivery systems. Magnetic nanoparticles（NPs）, especially SPIO nanoparticles, have long been used as MRI contrast agents and as an advantageous nanoplatform for drug delivery,taking advantage of their unique magnetic properties and ability to function at the molecular and cellular levels. Due to advances in nanotechnology, various means to control SPIO NPs＇ size, composition, magnetization and relaxivity have been developed, as well as ways to usefully modify their surface. Recently, self-assembly of SPIO NP clusters in particulate carriers — such as polymeric micelles, vesicles, liposomes, and layer-by-layer（Lb L） capsules — have been widely studied for application as ultrasensitive MRI probes, owing to their remarkably high spin–spin（T2） relaxivity and convenience for further functionalization.

Tetraphenylethylene-conjugated polycation covered iron oxide nanoparticles for magnetic resonance/optical dual-mode imaging

Magnetic resonance(MR)/optical dual-mode imaging with high sensitivity and high tissue resolution have attracted many attentions in biomedical applications.To avert aggregation-caused quenching of conventional fluorescence chromophores,an aggregation-induced emission molecule tetraphenylethylene(TPE)-conjugated amphiphilic polyethylenimine(PEI)covered superparamagnetic iron oxide(Alkyl-PEI-LAC-TPE/SPIO nanocomposites)was prepared as an MR/optical dual-mode probe.Alkyl-PEI-LAC-TPE/SPIO nanocomposites exhibited good fluorescence property and presented higher T2 relaxivity(352 Fe mM1s1)than a commercial contrast agent Feridex(120 Fe mM1s1)at 1.5 T.The alkylation degree of Alkyl-PEI-LAC-TPE effects the restriction of intramolecular rotation process of TPE.Reducing alkane chain grafting ratio aggravated the stack of TPE,increasing the fluorescence lifetime of Alkyl-PEI-LAC-TPE/SPIO nanocomposites.Alkyl-PEI-LAC-TPE/SPIO nanocomposites can effectively labelled HeLa cells and resulted in high fluorescence intensity and excellent MR imaging sensitivity.As an MR/optical imaging probe,Alkyl-PEI-LAC-TPE/SPIO nanocomposites may be used in biomedical imaging for certain applications.

磁共振靶向成像检测心肌纤维化大鼠模型中TGF-β1表达的实验研究

目的构建载转化生长因子-β1(transforming growth factor beta-1,TGF-β1)的超小超顺磁性氧化铁(ultrasmall supperparamagnetic iron oxide,USPIO)靶向探针(USPIO-anti-TGF-β1),探究其表征及磁共振成像(magnetic resonance imaging,MRI)靶向检测大鼠心肌纤维化(myocardial fibrosis,MF)模型中TGF-β1表达的可行性。材料与方法选择40只雄性SD大鼠,其中30只采用异丙肾上腺素(isoprenaline,ISO)皮下注射法建立MF模型,另外10只作为健康对照组。通过超声评估大鼠模型建立情况。将造模成功的30只大鼠随机分为实验组、单纯对照组及空白对照组,每组10只;构建USPIO-anti-TGF-β1靶向探针,通过尾静脉注入实验组大鼠体内,单纯对照组及空白对照组分别注入相同剂量的USPIO和生理盐水,并于注射12 h后行T2序列扫描。扫描完成后取大鼠心肌标本行病理学分析。采用独立样本t检验对给药前后的MRI信号强度变化进行分析。结果MRI示实验组给药前心肌信号尚均匀,给药12 h后心内膜下心肌可见信号减低区,二者相对信号强度具有明显差异(0.72±0.12 vs.0.62±0.10,P<0.01);单纯对照组与空白对照组给药前后心肌信号未见明显减低(0.73±0.12 vs.0.71±0.12,P=0.81;0.70±0.13 vs.0.74±0.13,P=0.52)。普鲁士蓝染色显示实验组MF区域与给药后MRI所示信号减低区相符合,免疫组化可见MF区域TGF-β1的阳性表达,普鲁士蓝染色显示心肌细胞中有大量铁颗粒的沉积,证实USPIO-anti-TGF-β1靶向探针的存在。结论通过USPIO-anti-TGF-β1靶向探针进行MRI在体检测MF大鼠模型中TGF-β1的表达可行,为临床监测TGF-β1的表达及抗MF治疗方案的选择和疗效评估提供了实验依据。

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.

超顺磁性氧化铁纳米颗粒标记靶向癌胚抗原的CAR-T细胞及体外磁共振成像研究

目的采用超顺磁性氧化铁纳米颗粒(superparamagnetic iron oxide nanoparticles,SPIONs)标记靶向癌胚抗原(carcinoembryonic antigen,CEA)的嵌合抗原受体T细胞(chimeric antigen receptor T cells,CAR-T细胞),并进行体外磁共振成像研究,为监测CEA CAR-T细胞的体内回输治疗提供依据。方法将ferumoxytol、肝素钠和硫酸鱼精蛋白分别以高(ferumoxytol 100μg/mL,肝素钠4 IU/mL,硫酸鱼精蛋白120μg/mL)、中(ferumoxytol 50μg/mL,肝素钠2 IU/mL,硫酸鱼精蛋白60μg/mL)、低(ferumoxytol 25μg/mL,肝素钠1 IU/mL,硫酸鱼精蛋白30μg/mL)剂量混合形成SPIONs复合物FHP(ferumoxytol/heparin/protamine),然后与CEA CAR-T细胞共孵育进行细胞标记。CCK-8、EdU和流式细胞术检测FHP对细胞的生物相容性,普鲁士蓝染色检测细胞对FHP的摄入情况,电感耦合等离子体-质谱法(inductively coupled plasma-mass spectrometry,ICP-MS)定量检测细胞中Fe含量,流式细胞术检测FHP标记的CEA CAR-T细胞对肿瘤细胞的杀伤作用,磁共振成像(magnetic resonance imaging,MRI)扫描FHP标记的CEA CAR-T细胞。结果高、中、低剂量的FHP对CEA CAR-T细胞的活力没有明显影响,CCK-8实验显示细胞活性均在100%以上;EdU实验显示各组细胞DNA复制活性均在94.3%以上。普鲁士蓝染色显示CEA CAR-T细胞可摄取FHP,且随FHP浓度的增加,摄取量增大。ICP-MS进一步检测显示胞内Fe含量为(440.23±189.36)ng/mL。肿瘤细胞杀伤实验表明FHP标记的CEA CAR-T细胞的杀伤肿瘤细胞能力良好。MRI扫描显示随着FHP浓度的增高,FHP标记的CEA CAR-T细胞T2WI信号呈明显降低趋势(P<0.01)。结论SPIONs复合物FHP具有良好的生物相容性并能够有效标记CEA CAR-T细胞,可作为CEA CAR-T细胞的磁标记物,为临床提供一种可行的MRI示踪方法。

Amphiphilic dextran/magnetite nanocomposites as magnetic resonance imaging probes

Superparamagnetic iron oxide (SPIO) nanoparticles are effective contrast agents for enhancement of magnetic resonance imaging at the tissue, cellular or even molecular levels. High quality SPIO nanoparticles can be synthesized in the organic phase but need to be transferred into water before any biomedical applications. In this study, amphiphilic poly(ε-caprolactone) grafted dextran (Dex-g-PCL) was used as carriers for particle encapsulation and stabilization in the aqueous phase. Multiple SPIO nanoparticles were self-assembled together with the help of Dex-g-PCL during phase transfer from chloroform to water, and diameters of Dex-g-PCL/SPIO nanocomposites were (64 ± 22) nm through dynamic light scattering measurement. These nanocomposites were superparamagnetic at 300 K with saturated magnetization of 88 emu/g Fe. In the magnetic field of 1.5 T, Dex-g-PCL/SPIO nanocomposites had a T2 relaxivity of 363 Fe mL·mol-1·s-1. This unique nanocomposite brought significant mouse liver contrast with signal intensity changes of -60% at 5 min after intravenous administration. However, uptake of Dex-g-PCL/SPIO nanocomposites in liver reticuloendothelial cells (Kupffer cells) did not immediately happen at shorter time points (<4 h) as verified by histology studies, and it was evident that more iron staining would be located in Kupffer cells 24 h after contrast agent administration. After 24 h and 10 d, the signal intensities (SI) gradually recovered, and SI changes were -44% and -31%, respectively. From our observation, the time window for enhanced-MRI could last at least 12 days and totally recovered after 16 days. This novel sensitive MRI contrast agent may find potential applications in discovering small liver lesions such as early tumor diagnosis.

Detection of neural stem cells function in rats with traumatic brain injury by manganese-enhanced magnetic resonance imaging

Background Previously we had successfully tracked adult human neural stem cells （NSCs） labeled with superparamagnetic iron oxide particles （SPIOs） in host human brain after transplantation in vivo non-invasively by magnetic resonance imaging （MRI）. However, the function of the transplanted NSCs could not be evaluated by the method. In the study, we applied manganese-enhanced MRI （ME-MRI） to detect NSCs function after implantation in brain of rats with traumatic brain injury （TBI） in vivo. Methods Totally 40 TBI rats were randomly divided into 4 groups with 10 rats in each group. In group 1, the TBI rats did not receive NSCs transplantation. MnCI2＂4H20 was intravenously injected, hyperosmolar mannitol was delivered to disrupt rightside blood brain barrier, and its contralateral forepaw was electrically stimulated. In group 2, the TBI rats received NSCs （labeled with SPIO） transplantation, and the ME-MRI procedure was same to group 1. In group 3, the TBI rats received NSCs （labeled with SPIO） transplantation, and the ME-MRI procedure was same to group 1, but diltiazem was introduced during the electrical stimulation period. In group 4, the TBI rats received phosphate buffered saline （PBS） injection, and the ME-MRI procedure was same to group 1. Results Hyperintense signals were detected by ME-MRI in the cortex areas associated with somatosensory in TBI rats of group 2. These signals, which could not be induced in TBI rats of groups 1 and 4, disappeared when diltiazem was introduced in TBI rats of group 3. Conclusion In this initial study, we mapped implanted NSCs activity and its functional participation within local brain area in TBI rats by ME-MRI technique, paving the way for further pre-clinical research.

超顺磁性氧化铁纳米粒子在肿瘤诊断及治疗方面的应用

超顺磁性氧化铁纳米粒子(superparamagnetic iron oxide nanoparticle, SPION)由于其独特的性质,如低毒、生物相容性、强大的磁性,以及在多功能模式中的优越作用,在肿瘤诊断、构建多模态肿瘤分子影像探针及治疗方面展现出巨大的潜力,今后可以在临床上提高肿瘤诊断的特异性、敏感性,实现诊疗一体化,本文从SPION的成像机制、合成方法出发,阐述近年来SPION在肿瘤的各种靶向成像、多模态成像和治疗方面的研究进展,展望未来SPION在肿瘤诊断及治疗中的发展前景,旨在为更好地构建基于SPION的新型诊疗一体化肿瘤探针提供参考。

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.

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.