CENIMAT I3N DCM FCT UNL

Charneca, Portugal

CENIMAT I3N DCM FCT UNL

Charneca, Portugal
SEARCH FILTERS
Time filter
Source Type

Cachitas H.,University of Lisbon | Sebastiao P.J.,University of Lisbon | Feio G.,CENIMAT I3N DCM FCT UNL | Vaca Chavez F.,University of Lisbon
Liquid Crystals | Year: 2014

Proton nuclear magnetic resonance (1H NMR) relaxometry, over about five decades in Larmor frequency, and pulsed field gradient NMR were used to study the molecular dynamics in the chromonic nematic and isotropic phases of stacked molecules of the binary mixture composed by Edicol Sunset Yellow (ESY) and deuterated water. Our results evidence that in both phases collective motions are responsible for the spin-lattice relaxation dispersion in the Larmor frequency range below 1 MHz. In the nematic phase, the collective motion are attributed to columnar undulations within the stacked molecules, while, in the isotropic phase, the results are explained by local order fluctuations due to the formation of the stacks. The high frequency dispersion was explained by individual molecular motions like rotations around and perpendicular to the stack axis, and also self-diffusion. © 2014 © 2014 Taylor & Francis.


Cardoso B.D.P.,University of Lisbon | Vicente A.I.,University of Lisbon | Ward J.B.J.,Royal College of Surgeons in Ireland | Sebastiao P.J.,University of Lisbon | And 7 more authors.
Inorganica Chimica Acta | Year: 2015

Three iron(III) complexes with ligands derived from N-ethyl-N-(2-aminoethyl)salicylaldiminate (H, 1; 5-Br, 2; 3-OMe, 3 substituents at the phenyl group) were prepared and the X-ray crystal structures of 1 and 2 are reported. NMR studies of solutions of these complexes in DMSO allowed for investigation of their magnetic behaviour and paramagnetic relaxation contribution. The relaxivities measured ranged from 0.35 to 0.80 mM-1 s-1 for proton Larmor frequencies from 0.01 to 300 MHz, in agreement with those known for other iron(III) based contrast agents. Biological studies on colonic epithelial T84 cell monolayers showed that the compounds exert toxic effects only at concentrations higher than 100 μM while coincidently reducing colonic epithelial secretory function. These two features make these complexes good candidates for further development in order to be used as MRI contrast agents. ©2015 Elsevier B.V. All rights reserved.


Carvalho A.,CENIMAT I3N DCM FCT UNL | Goncalves M.C.,University of Lisbon | Martins M.B.F.,IMed FF UL | Meixedo D.,CENIMAT I3N DCM FCT UNL | Feio G.,CENIMAT I3N DCM FCT UNL
Magnetic Resonance Imaging | Year: 2013

We present relaxivities measurements for both the longitudinal and transverse relaxations of two types of liposomes loaded with ultra small superparamagnetic iron oxide nanoparticles. The magnetoliposome systems presented are soybean phosphatidylcholine liposomes, with and without cholesterol, in the phospholipid bilayer with different molar ratios lipid:cholesterol. In fact, cholesterol is needed to obtain stable liposomes for intravenous administration. The longitudinal and transverse relaxivities were measured with a NMR spectrometer in a 7T magnetic field. For the studied concentrations, the liposomes show a negligible effect on the longitudinal relaxation time T1 of the medium, but they are very efficient on decreasing the transverse relaxation time T2, the behaviour one expects for a negative CA. We observed a lower transverse relaxivity for the magnetoliposome nanosystem with cholesterol, which strongly decreases with the cholesterol content in the liposome bilayer. © 2013 Elsevier Inc.


PubMed | CENIMAT I3N DCM FCT UNL
Type: Journal Article | Journal: Magnetic resonance imaging | Year: 2013

We present relaxivities measurements for both the longitudinal and transverse relaxations of two types of liposomes loaded with ultra small superparamagnetic iron oxide nanoparticles. The magnetoliposome systems presented are soybean phosphatidylcholine liposomes, with and without cholesterol, in the phospholipid bilayer with different molar ratios lipid:cholesterol. In fact, cholesterol is needed to obtain stable liposomes for intravenous administration. The longitudinal and transverse relaxivities were measured with a NMR spectrometer in a 7T magnetic field. For the studied concentrations, the liposomes show a negligible effect on the longitudinal relaxation time T1 of the medium, but they are very efficient on decreasing the transverse relaxation time T2, the behaviour one expects for a negative CA. We observed a lower transverse relaxivity for the magnetoliposome nanosystem with cholesterol, which strongly decreases with the cholesterol content in the liposome bilayer.

Loading CENIMAT I3N DCM FCT UNL collaborators
Loading CENIMAT I3N DCM FCT UNL collaborators