Lipid-Polymer Membranes as Carrier for L-Tryptophan: Molecular and Metabolic Properties

CHIARAMONI, NADIA SILVIA; FERNANDEZ RUOCCO MARIA JULIETA; SIRI MACARENA; IGARTÚA, DANIELA; PRIETO MARIA JIMENA; ALONSO, SILVIA DEL VALLE

Philadelphia

Congreso; Congreso anual de Biophysical Society (USA); 2013

Biophysical Society USA

A study of the lipopolymers that encapsulate L-tryptophan was carried out with the main goal of obtaining and characterizing vehicles that could be used as drug delivery systems for the treatment of several metabolic diseases that need an incremented systemic L-tryptophan concentration. Polymeric liposomes were obtained by UV irradiation of vesicles containing 1,2-bis(10,12-tricosadiynoyl)-sn-glycero-3-phosphocholine (DC8,9PC) and 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) in 1:1 molar ratio. These polymeric liposomes were also obtained in presence of 10 and 50 mol % of L-tryptophan (respect to total lipid concentration). Polymerization efficiency in presence of the two mentioned L-tryptophan concentration were studied spectrofotometrically; along with bilayer packing at the polar head region with the probe Merocyanine 540 (MC540). Interaction between lipid-polymer membranes and L-tryptophan was followed by FTIR. Results showed that high L-tryptophan concentration induce the formation of lipopolymers with higher polymeric units, leaded by the higher lipid rigidity adopted in presence of high amino acid concentration. This is a derived implication of the L-tryptophan preferential position interacting at the amine terminal of the choline group. Stability of lipopolymers with different amounts of L-tryptophan was also studied through release profiles. L-tryptophan release was induced by a concentration gradient and amino acid concentration was determined spectrofotometrically. Polymeric liposomes were able to retain around 80 % of the L-tryptophan after 24 hour. Then, polymeric liposomes with 10 mol % of the amino acid release 5 % more. Nonetheless, retention was high in the elapsed time analysed. Metabolic activity of the Caco-2 cell line was also studied in the presence of polymeric liposomes with both L-tryptophan concentrations. Cytotoxic effects were low. In resume, polymeric liposomes studied in this work could be applied as drug delivery systems in order to improve L-tryptophan pharmacodynamics.