Liposomes as a potential drug carrier for citicoline (CDP-choline) and the effect of formulation conditions on encapsulation efficiency.

In this paper we report the investigation of the potential of liposomes as drug carrier for citicoline (1; CDP-choline). The aim of our work is to improve the pharmacokinetic and pharmacodynamic parameters of the drug to facilitate the overcoming of the blood-brain barrier. The thermotropic behaviour of hydrated dispersions of various phospholipids and their mixtures containing 1 have been investigated by differential scanning calorimetry (DSC) to have a clear view of the interaction between the drug and the liposome phospholipids. By the values of transition peak temperature (Tm) and transition enthalpy (delta H) we note a strong interaction between 1 and the polar heads of L-alpha-dipalmitoylphosphatidic acid (DPPA) and L-alpha-dipalmitoylphosphatidylserine (DPPS), whereas there is not any considerable interaction between the drug and L-alpha-dipalmitoylphosphatidylcholine (DPPC) or L-alpha-dimyristoylphosphatidylcholine (DMPC); in any case no interaction occurs between 1 and the hydrophobic part of the phospholipid. So we conclude that all the drug is fitted into the aqueous spaces. The results of the encapsulation efficiency experiments demonstrate how the encapsulation capacity increase with using charged phospholipids, reaching the top with DPPA. Moreover, it was noted that the presence of Cholesterol (Chol) enhances the encapsulation capacity (EC) and drug content (DC) values of DPPC, a neutral phospholipid. The size of the liposomes was determined by light scattering (LS).