Micro-CT myelography using contrast-enhanced digital subtraction: feasibility and initial results in healthy rats.

PURPOSE: The spinal subarachnoid space (SSAS) is vital for neural performance. Although models of spinal diseases and trauma are used frequently, no methods exist to obtain high-resolution myelograms in rodents. Thereby, our aim was to explore the feasibility of obtaining high-resolution micro-CT myelograms of rats by contrast-enhanced dual-energy (DE) and single-energy (SE) digital subtraction. METHODS: Micro-CT contrast-enhanced DE and SE imaging protocols were implemented with live adult rats (total of 18 animals). For each protocol, contrast agents based on iodine (Iomeron® 400 and Fenestra® VC) and gold nanoparticles (AuroVist™ 15 nm) were tested. For DE, images at low- and high-energy settings were acquired after contrast injection; for SE, one image was acquired before and the other after contrast injection. Post-processing consisted of region of interest selection, image registration, weighted subtraction, and longitudinal alignment. RESULTS: High-resolution myelograms were obtained with contrast-enhanced digital subtraction protocols. After qualitative and quantitative (contrast-to-noise ratio) analyses, we found that the SE acquisition protocol with Iomeron® 400 provides the best images. 3D contour renderings allowed visualization of SSAS and identification of some anatomical structures within it. CONCLUSION: This in vivo study shows the potential of SE contrast-enhanced myelography for imaging SSAS in rat. This approach yields high-resolution 3D images without interference from adjacent anatomical structures, providing an innovative tool for further assessment of studies involving rat SSAS.

Biodistribution and Tumor Uptake of 67Ga-Nimotuzumab in a Malignant Pleural Mesothelioma Xenograft.

Malignant pleural mesothelioma (MPM) is the most common tumor of the pulmonary pleura. It is a rare and aggressive malignancy, generally associated with continuous occupational exposure to asbestos. Only a multimodal-approach to treatment, based on surgical resection, chemotherapy and/or radiation, has shown some benefits. However, the survival rate remains low. Nimotuzumab (h-R3), an anti-EGFR (epidermal growth factor receptor) humanized antibody, is proposed as a promising agent for the treatment of MPM. The aim of this research was to implement a procedure for nimotuzumab radiolabeling to evaluate its biodistribution and affinity for EGF (epidermal growth factor) receptors present in a mesothelioma xenograft. Nimotuzumab was radiolabeled with 67Ga; radiolabel efficiency, radiochemical purity, serum stability, and biodistribution were evaluated. Biodistribution and tumor uptake imaging studies by microSPECT/CT in mesothelioma xenografts revealed constant nimotuzumab uptake at the tumor site during the first 48 h after drug administration. In vivo studies using MPM xenografts showed a significant uptake of this radioimmunoconjugate, which illustrates its potential as a biomarker that could promote its theranostic use in patients with MPM.

Biodistribution and Lymphatic Tracking of the Main Neurotoxin of Micrurus fulvius Venom by Molecular Imaging.

The venom of the Eastern coral snake Micrurus fulvius can cause respiratory paralysis in the bitten patient, which is attributable to ß-neurotoxins (ß-NTx). The aim of this work was to study the biodistribution and lymphatic tracking by molecular imaging of the main ß-NTx of M. fulvius venom. ß-NTx was bioconjugated with the chelator diethylenetriaminepenta-acetic acid (DTPA) and radiolabeled with the radionuclide Gallium-67. Radiolabeling efficiency was 60%-78%; radiochemical purity ≥92%; and stability at 48 h ≥ 85%. The median lethal dose (LD50) and PLA2 activity of bioconjugated ß-NTx decreased 3 and 2.5 times, respectively, in comparison with native ß-NTx. The immune recognition by polyclonal antibodies decreased 10 times. Biodistribution of ß-NTx-DTPA-(67)Ga in rats showed increased uptake in popliteal, lumbar nodes and kidneys that was not observed with (67)Ga-free. Accumulation in organs at 24 h was less than 1%, except for kidneys, where the average was 3.7%. The inoculation site works as a depot, since 10% of the initial dose of ß-NTx-DTPA-(67)Ga remains there for up to 48 h. This work clearly demonstrates the lymphatic system participation in the biodistribution of ß-NTx-DTPA-(67)Ga. Our approach could be applied to analyze the role of the lymphatic system in snakebite for a better understanding of envenoming.

Ozone Dosage Effect on C6 Cell Growth: in Vitro and in Vivo Tests.

C6 rat glioma cells are one of the most aggressive carcinogenic tumors, due to its high mortality rate in human beings and animals. The current treatment for this illness includes surgery, radio and chemotherapy, showing relapse in patients treated with those therapies. Since the ozone was found to be an effective bioreactive to inhibit growth of several carcinoma cells in vitro and in vivo. In this research, therapeutic peritoneum insufflation of ozone/oxygen dissolved in the physiological solution of NaCl 0.9% was dosed for fifteen days on different female mice groups in an advanced stage of C6 tumor (n=6). The first of them was the control group which had no treatment, the second group was dosage with oxygen every second day, the third group was dosed with ozone every second day, and finally the fourth group was dosed with ozone dissolved every fifth day. The size of the tumor was higher in both groups dosage by ozone, nevertheless tumor activity measured by microPET was 98% less in the fourth group compared with the control group. That result proves that ozone provokes an increase in the tumor volume even though the decrease of the cell activity. Those results were confirmed by the quantification of hydroperoxides, total cholesterol and total triglycerides.

Design and biological evaluation of 99mTc-N2S2-Tat(49-57)-c(RGDyK): a hybrid radiopharmaceutical for tumors expressing α(v)ß(3) integrins.

UNLABELLED: The α(ν)ß(3) integrin is over-expressed in the tumor neovasculature and the tumor cells of glioblastomas. The HIV Tat-derived peptide has been used to deliver various cargos into cells. The aim of this research was to synthesize and assess the in vitro and in vivo uptake of (99m)Tc-N2S2-Tat(49-57)-c(RGDyK) ((99m)Tc-Tat-RGD) in α(ν)ß(3) integrin positive cancer cells and compare it to that of a conventional (99m)Tc-RGD peptide ((99m)Tc-EDDA/HYNIC-E-[c(RGDfK)]2). METHODS: The c(RGDyK) peptide was conjugated to a maleimidopropionyl (MP) moiety through Lys, and the MP group was used as the branch position to form a thioether with the Cys(12) side chain of the Tat(49-57)-spacer-N2S2 peptide. (99m)Tc-Tat-RGD was prepared, and stability studies were carried out by size exclusion HPLC analyses in human serum. The in vitro affinity for α(v)ß(3) integrin was determined by a competitive binding assay. In vitro internalization was determined using glioblastoma C6 cells. Biodistribution studies were accomplished in athymic mice with C6 induced tumors that had blocked and unblocked receptors. Images were obtained using a micro-SPECT/CT. RESULTS: (99m)Tc-Tat-RGD was obtained with a radiochemical purity higher than 95%, as determined by radio-HPLC and ITLC-SG analyses. Protein binding was 15.7% for (99m)Tc-Tat-RGD and 5.6% for (99m)Tc-RGD. The IC50 values were 6.7 nM ((99m)Tc-Tat-RGD) and 4.6 nM ((99m)Tc-RGD). Internalization in C6 cells was higher in (99m)Tc-Tat-RGD (37.5%) than in (99m)Tc-RGD (10%). Biodistribution studies and in vivo micro-SPECT/CT images in mice showed higher tumor uptake for (99m)Tc-Tat-RGD (6.98% ± 1.34% ID/g at 3h) than that of (99m)Tc-RGD (3.72%±0.52% ID/g at 3h) with specific recognition for α(v)ß(3) integrins. CONCLUSIONS: Because of the significant cell internalization (Auger and internal conversion electrons) and specific recognition for α(v)ß(3) integrins, the hybrid (99m)Tc-N2S2-Tat(49-57)-c(RGDyK) radiopharmaceutical is potentially useful for the imaging and possible therapy of tumors expressing α(v)ß(3) integrins.