Water and membrane dynamics of polyethylene glycol (PEG) grafted vesicles

EDUARDO M. CLOPE; ANA K. CHATTAH; MARÍA A. PERILLO

Tucumán

Conferencia; XLI Reunión Anual de la Sociedad Argentina de Biofísica; 2012

Sociedad Argentina de Biofísica

PEG grafted phospholipids are used in nanoparticles formation for drug encapsulation and transport. PEG chains form an interphasial hydrophilic layer that prevents aggregation and nonspecific binding. Recently, from NMR measurements of spin-lattice relaxation times (T1) of PEG6000 solutions, we reported the presence of two molecular populations, both in water and in PEG as well as a PEG6000 aggregation also supported by dynamic light scattering. In the present work we study the water dynamics by NMR in vesicles formed by binary mixtures DPPC:PE-PEG (9:1) where PE (dipalmitoylphosphatidylethanolamine) is covalently modified with PEG of different molecular masses (350, 1000 and 5000 Da.). 1H-T1 was measured in a 400 MHz Bruker spectrometer. Liposomes were dispersed in D2O, enabling the spectral resolution of signals belonging to protons from phospholipids polar head (PH) and hydrocarbon chain (HC), PEG moiety and residual H2O.. The results showed the presence of two components (T1A and T1B, long and short times respectively) both in water and in phospholipids.