Magnetic Resonance Iron Nanoparticles Imaging Technology Basic Experimental Research In The Tumor And Lymph Node Metastases

Purpose To study magnetic resonance enhancement features of inflammatory lymph nodes using different doses of ultrasmall superparamagnetic iron oxide (USPIO) particles in order to establish a standardized protocol for USPIO-enhanced MR imaging of lymph nodes. Materials and Methods A total of 12 healthy New Zealand rabbits were injected complete Freund's adjuvant in foot pad to establish popliteal inflammatory lymph node model. Different doses (45/90/135μmol Fe/kg) of USPIO were injected intravenously. Magnetic resonance scans were performed before and after USPIO injection to observe the enhancement features of different groups. T1SI, T2SI, T2*value and T2 value were measured and T2 enhancement ratio was calculated at different time points to draw time-dependent curves.Results Twenty-four hours after USPIO injection, there was no statistical difference in T2SI and enhancement ratio between 90 and 135μmol Fe/kg dose groups, but both were superior to 45μmol Fe/kg group (P<0.05); There were no statistical differences in T1SI, T2SI, T2 value or enhance ratio from 6 to 24 hours after USPIO injection in 90μmol Fe/kg group (P>0.05), and signal reduction of lymph nodes peaked 18 hours after injection. Better images were acquired with a post-contrast delay of 18-24 hours. Conclusion Lymph nodes can be enhanced well with a dose of 90μmol Fe/kg. Postcontrast delay of 18-24 hours is appropriate for acquiring satisfactory enhancement images. Purpose To assess the characteristics of lymph nodes in USPIO enhanced Magnetic resonance (MR) imaging in rabbit tumor and inflammatory models, and explore its relevance with histologic ultrastructural findings; To discuss the accuracy and clinical value of USPIO enhanced MR imaging in the diagnosis of lymph node.Materials and Methods 36 New Zealand white rabbits were randomly divided into inflammatory group and tumor group. Complete Freund's adjuvant was injected into the footpads to set up inflammatory model. VX2 tumor cell suspension was implanted into thighs to set up metastatic lymph node model. MR scans of the popliteal fossa were performed before and 24 hours after USPIO (90μmol Fe/kg) administration. T2 values of each lymph node were measured and enhancement rate was calculated as well. HE staining, Prussian blue staining, and electronic microscopy were performed to observe the pathological microstructure changes and the distribution of the iron particle in lymph node. Relationship between lymph nodes USPIO enhancement imaging and its microstructures were further analyzed. Diagnoses of popliteal lymph nodes were evaluated based on dedicated criteria and the accuracy was also discussed. Results There were 46 inflammatory and 26 metastatic lymph nodes, including four with subcapsular metastatic foci. Sensitivity, specificity and positive and negative predictive values of the diagnosis of nodal metastasis were 84.6%,87.0%,78.6% and 90.9%, respectively. Plain scan showed no obvious difference of T2 signal intensity between the inflammatory and metastasis lymph nodes. After USPIO administration, there was distinctly T2 signal reduction at the center in inflammatory lymph nodes, and metastatic lymph nodes showed faint T2 signal reduction. Enhancement rate of benign and malignant lymph nodes were 57.22% and 29.45%, respectively (P< 0.01). HE staining and Prussian blue staining indicated USPIO particles located mainly in the macrophages at inflammatory lymphatic medulla, while paracortical area and cortical area contained relatively much less USPIO particles due to less macrophages distribution. MRI findings were correlated with the pathological results. Electronic microscopy also verified that the majority of USPIO particles were located in the numerous cytophagic bubbles of macrophages in inflammatory nodes, while in metastatic nodes, they contained predominantly cellular residues.Conclusion USPIO-enhanced MR is a particularly promising technique that improves the sensitivity and specificity of metastatic lymph node. USPIO enhancement pattern of different lymph nodes is closely related to distribution and functional status of the intra-node macrophages. It may affect the accuracy of the lymph node property diagnosis based on USPIO enhanced image. Purpose:To investigate granulometric characteristics of DMSA modified Ultrasmall Superparamagnetic Iron Oxide (USPIO) nanoparticles, the magnetic property in vitro and distribution features in healthy nude mice.Materials and Methods:FT-IR method was used to detect carboxyl groups on the surface of DMSA-USPIO. MR signal intensity of modified USPIO solutions with different concentrations was evaluated, and was compared with that of Ferumoxtran-10 solutions. USPIO nanoparticles were injected into 3 healthy BALB/C nu-nu nude mice through tail veins. MR imaging was performed before and after USPIO administration to study the MR enhancement features and T2 signal intensity changes on different time points in liver, kidney, muscle and brain. Mice were sacrificed right after MR imaging scan, tissues were collected for Prussian blue staining to investigate iron distribution in different organs.Results:DMSA-USPIO had absorption peaks at CO-and OH-groups. R2 and R2* values had a linear correlation with USPIO concentrations in both particles. At the same concentration, T2 and T2* relaxation time of DMSA-USPIO nanoparticles was obviously shorter than that of Ferumoxtran-10. After USPIO administration, T2 signal intensity of liver reduced significantly, whereas no obvious T2 signal intensity changes was found in kidney, muscle and brain. T2 values of liver showed significant differences between pre-and 24 hours post-USPIO administration (p<0.05), with an enhancing ratio of 26.8%. Prussian blue staining showed iron nanoparticles scattering in liver, spleen and lymph nodes, and there were no visible iron deposition in other tissues including kidney, brain, lung, myocardiac wall and bowel wall.Conclusion:DMSA-USPIO nanoparticles with superb magnetic features, which were encapsulated with rich modifiable surface groups, can be used as conjugation carrier of the target molecular for MR imaging. The significant T2 value enhancement in the liver might be recommended as one of indexes for evaluation of USPIO enhancement effectiveness. Purpose:To establish a magnetic resonance molecular conjugator of vascular endothelial growth factor receptor 3 (VEGFR3) antibody and ultrasmall superparamagnetic iron oxide particles (USPIO). And to investigate in vitro targeted combination specificity and MRI targeted imaging feasibility of VEGFR3-USPIO to human breast cancer MDA-MB-231 cells.Materials and Methods:Expression level and expression site of VEGFR3 on MDA-MB-231 cells was detected using immunofluorescence technique. Molicular weight measurement and semi-quantitative analysis were performed using Western Blot test. VEGFR3 anti-body and USPIO were coupled using carbodiimide (1-ethyl-(3-dimethylamino propyl) carbodiimide hydrochloride (EDC). T2 relaxation time differences of VEGFR3-USPIO conjugator and USPIO solutions were evaluated at same concentration grads. After incubating the MDA-MB-231 cells with VEGFR3-USPIO and USPIO respectively, existing of iron particles was observed by Prussian blue staining, changes of T2 relaxation time of each in vitro samples were measured using a clinical MRI scanner.Results:VEGFR3 receptor expression was positive both on the membrane and in the cytoplasm of MDA-MB-231 cells. Molecular weight of VEGFR3 peptide is about 73Kda according to the result of Western blot test. In vitro MR scan proved that there was no significant T2 or T2* relaxition time difference between VEGFR3-USPIO and USPIO at every different concentrations, and there was linear correlation between R2 and R2* relaxation time and the particle concentration. After incubation, Prussian blue staining showed more iron particles left in the VEGFR3-USPIO group. Distribution of iron particles was mainly around the cell membrane in the VEGFR3-USPIO group, while scattered iron particles were found in the inter-cell space. T2 relaxation time of VEGFR3-USPIO-cell incubation group was lower than USPIO-cell incubation group, T2 relaxation time change rate were 61.0% and 43.5% respectively.Conclusion:VEGFR3-USPIO conjugator had satisfied in vitro targeted combination specificity and MRI targeted imaging feasibility according to a VEGFR3 expression positive cell MDA-MB-231. Purpose:To investigate the distribution feature of VEGFR3 antibody-conjugated Ultrasmall Superparamagnetic Iron Oxide nanoparticles (VEGFR3-USPIO) in healthy nude mice and assess its targeted imaging viability in the tumor bearing nude mice using a clinical type MRI scanner.Materials and Methods:VEGFR3-USPIO molecular probes were injected into 3 healthy BALB/C nu-nu nude mice via tail veins. MR imaging including multiple sequences was performed pre-and post-VEGFR3-USPIO administration in order to study the MR enhancement features and T2 signal intensity changes on different time points in liver, kidney, muscle and brain. Mice were sacrificed right after MR imaging scan, tissues were collected for Prussian blue staining. Iron particles distribution in different organs was investigated. Subcutaneous human mammary tumor (MDA-MB-231) models were established in 6 BALB/C nu-nu female nude mice. They were then randomly divided into two groups. VEGFR3-USPIO and DMSA-USPIO were injected into tumor bearing nude mice via tail veins. MR images were acquired before and 24 hours after contrast agent administration. T2 value enhancement of the tumor and the liver was measured and tissues were collected for histological examination.Results:After VEGFR3-USPIO administration in healthy nude mice, T2 value of liver got lower, whereas no obvious T2 value change was found in the kidney, muscle and brain. T2 values of the liver showed significant differences between before and 24 hours after VEGFR3-USPIO administration (p<0.05), with an enhancing ratio of 25.8%. Prussian blue staining showed iron oxide nanoparticles scattering in liver, spleen and lymph nodes, and there were no visible iron deposition in other tissues including kidney, brain, lung, myocardia wall and bowel wall. On T2WI image, T2 value of tumor tissue showed a dramatic decrease in VEGFR3-USPIO group, with enhancing ratio of 28.6%. However, in the USPIO group, T2 value of tumor tissue had no obvious changes. In both groups, T2 value of the liver showed equally 30% reduction. Prussian blue staining in VEGFR3-USPIO group showed that blue iron nanoparticles scattered around the tumor cells or inside their stoma. While in USPIO group, iron nanoparticles mostly deposited surround the macrophages which gathered around the tumor tissue.Conclusion:Similar to DMSA-USPIO nanoparticle, VEGFR3-USPIO mainly distributed in the liver, spleen and lymph nodes. The significant T2 value enhancement in the liver might be recommended as one of indexes for evaluation of VEGFR3-USPIO enhancement effectiveness. VEGFR3-USPIO is a potentially superb MRI molecular targeted imaging probe with high efficiency and high specificity. It is possible to be used as an imaging tool for early tumor detection and non-invasive real-time evaluation of anti-tumor therapy.