Characterization of molecular dynamics and elastic properties of flexible liposomes membranes using proton FFC-NMR Relaxometry

MARÍA BELÉN MARZOLA CORONEL; CARLA CECILIA FRAENZA; ESTEBAN ANOARDO

Congreso; 10th Conference on Fast Field Cycling NMR Relaxometry; 2017

Flexible liposomes have proved to be a good strategy for transdermal drug delivery; therefore the characterization of the elastic properties of lipid membranes takes relevance, being conveniently described through the bending elastic modulus k . This constant has an inverse proportionalityrelation with the parameter called deformability or adaptability of the vesicles, being one of the most relevant parameters related to the penetration dynamics in the skin. In previous works [1-4], a model was presented to interpret the spin-lattice relaxation rate dispersion of protons, obtained with the fast field cycling nuclear magnetic relaxometry technique(FFC), for unilamellar liposomes. In addition to providing general information on the lipid dynamics, this model allows us to infer about the elastic properties of the liposomes by means of the elastic constant k , which is one of the physical parameters involved in the model. In order to extend this model for elastic vesicles, in this work we analyzed experimental relaxation dispersions obtained at different temperatures (291-328K) for liposomes of radius of 50nm, composed of SPC (soy phosphatidylcholine) with different ionic (sodium deoxycholate) and nonionic (Tween 80 and BrijO20) detergents added to enhance the membrane flexibility, at concentrations up to 40 mol%. The model was successfully extended for this type of liposomes. Variations in k were moderate (around 40%) in response to the additive concentration up to 20mol%. However, we observed some particular changes in the way diffusion and order fluctuations affect the proton spin-latticerelaxation as detergent concentration is increased, for the three used detergents.References[1] C. J. Meledandri, J. Perlo, E. Farrher, D. F. Brougham, E. Anoardo, J. Phys. Chem. B 113 (2009) 15532.[2] J. Perlo, C. J. Meledandri, E. Anoardo, D. F. Brougham J. Phys. Chem. B 115 (2011) 3444.[3] C. C. Fraenza, C. J. Meledandri, E. Anoardo, D. F. Brougham, ChemPhysChem 15 (2014) 425.[4]- G. A. Domingez, J. Perlo, C. C. Fraenza, E. Anoardo, Chem. Phys. Lipids 201 (2016) 21.