The elastic properties of flexible liposomes as mesured using fas field-cycling NMR relaxometry:influence of surfactant concentration and temperature

MARÍA BELÉN MARZOLA CORONEL; CARLA CECILIA FRAENZA; ESTEBAN ANOARDO

Congreso; EUROISMAR 2019; 2019

At present, the development of nanometric vesicles for drug delivery in the human body bydifferent routes has become of great interest for the pharmaceutical industry. Flexible liposomeshave proved to be useful for transdermal transport, therefore it is important to measure the bendingelastic modulus κ of the membrane.In previous works [1-5], a model was presented to interpret the spin-lattice relaxation ratedispersion 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 dyna-mics, this model allows us to infer about the elastic properties of the liposomes by means of theelastic constant κ , which is one of the physical parameters involved in the model. This modelhas been validated from measurements of κ for cholesterol doped vesicles and for surfactant dopedvesicles, in order to increase or decrease the value of the constant respectively.In order to study the influence of the temperature and the surfactants?s characteristics in thebehavior of the molecular parameteres in flexible liposomes, experiments using elastic vesicles wereperformed in this work. Specifically, we analyzed experimental relaxation dispersions obtained atfour different temperatures (291-328K) for liposomes of radius of 50nm, composed of SPC (soyphosphatidylcholine) with different detergents added to enhance the membrane flexibility, at con-centrations up to 20 mol.For the lowest temperature the elastic modulus of the membrane decrease with the addition ofsurfactant, as espected. In addition, after a correlation analysis, a great influence of some propertiesof the surfactant on especific phisical parameters of the sistem was found, for example a dependencebetween the molecular size of the surfactant and the behavior of κ with the temperature.References[1] C. J. Meledandri, J. Perlo, E. Farrher, D. F. Brougham, E. Anoardo, Interpretation of Molecular Dynamics on Different TimeScales in Unilamellar Vesicles Using Field-Cycling NMR Relaxometry. J. Phys. Chem. B 113: 15532-15540, 2009.[2] J. Perlo, C. J. Meledandri, E. Anoardo, D. F. Brougham Temperature and Size-Dependence of Membrane Molecular Dynamicsin Unilamellar Vesicles by Fast Field-Cycling NMR Relaxometry. J. Phys. Chem. B 115: 3444-3451, 2011.[3] C. C. Fraenza, C. J. Meledandri, E. Anoardo, D. F. Brougham, The Effect of Cholesterol on Membrane Dynamics on DifferentTimescales in Lipid Bilayers from Fast FieldCycling NMR Relaxometry Studies of Unilamellar Vesicles. ChemPhysChem 15: 425-435,2014.[4] G. A. Domingez, J. Perlo, C. C. Fraenza and E. Anoardo, Measurement of the Bending Elastic Modulus in Unilamellar VesiclesMembranes by Fast Field Cycling NMR Relaxometry. Chem. Phys. Lipids 201: 21-27, 2016.[5] C. C. Fraenza, E. Anoardo, Dynamical regimes of lipids in additivated liposomes with enhanced elastticity: A field-cyclingrelaxometry approach. Biophysical Chemistry 228: 38-46 2017.