Mirel Cabrera

M Cells Prefer Archaeosomes: An In Vitro/In Vivo Snapshot Upon Oral Gavage in Rats

The archaeolipids (lipids extracted from archaebacterias) are non saponificable molecules that form self sealed mono or bilayers (archaeosomes-ARC). Different to liposomes with bilayers made of conventional glycerophospholipids, the bilayer of ARC posses a higher structural resistance to physico chemical and enzymatic degradation and surface hydrophobicity. In this work we have compared the binding capacity of ARC exclusively made of archaeols containing a minor fraction of sulphoglycophospholipids, with that of liposomes in gel phase on M-like cells in vitro. The biodistribution of the radiopharmaceutical (99m)Tc-DTPA loaded in ARC vs that of liposomes upon oral administration to Wistar rats was also determined. The fluorescence of M-like cells upon 1 and 2h incubation with ARC loaded with the hydrophobic dye Rhodamine-PE (Rh-PE) and the hydrophilic dye pyranine (HPTS) dissolved in the aqueous space, was 4 folds higher than upon incubation with equally labeled liposomes. Besides, 15% of Rh-PE and 13 % of HPTS from ARC and not from liposomes, were found in the bottom wells, a place that is equivalent to the basolateral pocket from M cells. This fact suggested the occurrence of transcytosis of ARC. Finally, 4 h upon oral administration, ARC were responsible for the 22.3 % (3.5 folds higher than liposomes) shuttling of (99m)Tc-DTPA to the blood circulation. This important amount of radioactive marker in blood could be a consequence of an extensive uptake of ARC by M cells in vivo, probably favored by their surface hydrophobicity. Taken together, these results suggested that ARC, proven their adjuvant capacity when administered by parenteral route and high biocompatibility, could be a suitable new type of nanoparticulate material that could be used as adjuvants by the oral route.

Development of 177Lu-DOTA-Dendrimer and Determination of Its Effect on Metal and Ion Levels in Tumor Tissue

Dendrimers are synthetic nanomolecules with well-defined chemical structures. Different strategies have been used for radiolabeling dendrimers with different radioisotopes. In this study, the aim was to conjugate dendrimers with (177)Lu, to observe the in vivo behavior of the labeled compound and to measure the elementary changes in tumor tissue that could be caused by ionizing radiation. PAMAM G4 dendrimers conjugated with DOTA were labeled with (177)Lu. The radiolabeled compound was characterized and its stability was evaluated by reverse phase high performance liquid chromatography. Radiolabeling yield was >98% and stable for 24 hours. Biodistribution studies of (177)Lu-DOTA-dendrimers in C57BL/6 melanoma-bearing mice showed blood clearance with hepatic and renal depuration and tumor uptake. The concentrations of Br, Ca, Cl, Fe, K, Mg, Na, Rb, S, and Zn were determined in tumor tissues of C57BL/6 mice treated with (177)Lu-DOTA-dendrimers and in untreated mice. The results showed decreased concentrations of Br (62%), Ca (24%), Cl (51%), K (12%) and Na (60%) and increased concentrations of Fe (8%), Mg (28%), Rb (100%), S (6%) and Zn (4%) in tumor tissues of mice treated with (177)Lu-DOTA-dendrimers. These data may be useful to evaluate changes in tumor tissues as indicators of damage that could be caused by ionizing radiation.

99m Tc-Tricarbonyl- (2-amino- 5,10-dioxide- 7(8)-fluorophenazine) as Probe for Mammary Hypoxic-tumors Imaging

Our group has previously reported potential new radiopharmaceuticals, i.e. 99m Tc-tricarbonyl-(2-amino- 5,10-dioxide- 7(8)-fluorophenazine), Tc-FZ), with the ability to detect hypoxic tumoral tissues. Previously, this probe was used to detect solid tumors, employing a model of lung carcinoma generated by inoculation of 3LL Lewis murine cells in C57BL/6 mice. The resultsrevealed an adequate tumor/muscle ratio, 3.8 at 2 h post-injection (p.i.), with lower tumor/blood ratio, i.e. 0.6 at 2 h p.i.. Due to some models of breast cancer also being characterized by hypoxic areas, herein we decided to analyze the behavior of Tc-FZ in BALB/c mice bearing mammary tumor induced with 4T1-mouse tumoral cell line. The studied ratios revealed to be slightly a little more unfavorable than in the lung tumor-porting animals, being tumor/muscle and tumor/blood ratios, at 2 h p.i., of 3.0 and 0.23, respectively. Additionally, animals in vivo images showed that the liver masked tumor signal. AcknowledgementThe authors want to thank the ANII for financial support.

A novel method to radiolabel stealth liposome through 1,2- dimyristoyl-sn-glycero-3-phosphoethanolamine-N-DTPA with 99mTc and biological evaluation

Purpose : To study surface technetium labeling of stealth DTPA-Liposome and to evaluate its potential as a molecular imaging tracer for both normal and melanoma-bearing mice. The radiolabeling yield of liposomes was greater than 90% and showed good chemical and biological stability. Biodistribution studies in normal mice showed blood clearance with hepatic and renal depuration. Melanoma-bearing mice showed a similar pattern of biodistribution with high tumor uptake allowing tumor imaging. The developed method of surface radiolabeled DTPA-PEG-Liposomes with 99m Tc was effective and stable in vivo .