Interaction between phospholipids bilayer and chitosan in liposomes investigated by 31P NMR spectroscopy

The interaction between chitosan and the polar head of phosphatidylcholine (PC) is discussed for a composite nanovesicle obtained by incorporating chitosan in the organic phase before PC self-assembling. Nanovesicles free of chitosan are studied in parallel to allow the comparison concerning modifications produced on the composite system. Zeta Potential increases in the presence of chitosan and with the increase in its concentration proving the localization of the polymer over the external surface of the vesicle as one interaction site. A (31)P resonance around 0 ppm, characteristic of the system, is reduced with addition of chitosan at 25 degrees C, indicating motional freedom reduction of the polar head phosphate group. The same resonance signal remains almost constant after increasing the temperature to 60 degrees C, suggesting that chitosan shields the phospholipids polar heads as a consequence of the electrostatic interactions leading to an increase in the thermodynamic stability of the composite.