Characterization of liposome/ arsanilic acid drug delivery system

A. LIS FEMIA; S. AMOR; M. C. TAIRA; M. GRASSELLI; S. DEL V. ALONSO

Montevideo

Congreso; 6° International Conference of Biological Physics; 2007

IUPAB

It is well known the application of arsenic compounds on therapies for different kinds of cancer, like promyelocitic acute leukemia. Hereby is proposed arsanilic acid (AA) as an alternative arsenic drug, since its toxicity is lowered by liposome encapsulation, when compared with inorganic arsenic compounds. This presentation deals with liposomes/arsanilic acid system interaction. This study shows the special features generated by AA in contact with different lipid formulations when encapsulated/associated. Properties like size, interaction with probe MC540, encapsulation efficiency, lipid peroxidation and cytotoxicity are shown as a function of AA concentration, maintaining lipid concentration at 1 mM. Results observed showed that AA increases liposomal size, for example for AA (0.20 mM) changes from a range 200-400 nm to 400-600 nm. AA influence not only size but apparent equilibrium constant of a molecular probe. The MC 540 apparent equilibrium of dimerization constant, Kadd determined as (dim)/(mon)2. Data obtained for Kadd were in the range 10 7 - 10 6, observing an increment as a function of AA acid concentration. Encapsulation efficiency (Ee) determinations showed that percentage of drug incorporated into liposomes was 20-30% at 0.12 mM AA for EPC/SA (1:0.4 molar ratio), in different experimental conditions. These Ee are lower for EPC/Chol formulations. Also, lipid peroxidation gave results pointing that AA increase this parameter, which is concordant with cytotoxicity. This was also dependent on AA encapsulation concentration. Also a hydrophobicity factor (HF) was measured, and data obtained showed that the probe used partitioned between aqueous phase and hydrophobic lipid side chains depending on AA concentration.