Interaction of lipophilic gemcitabine prodrugs with biomembrane models studied by Langmuir-Blodgett technique

The stability and bioavalaibility of anticancer agents, such as gemcitabine, can be increased by forming prodrugs. Gemcitabine is rapidly deaminated to the inactive metabolite (2’,2’-difluorodeoxyuridine), thus to improve its stability a series of increasingly lipophilic gemcitabine prodrugs, linked through the 4-amino group to valeroyl, lauroyl and stearoyl acyl chains, were synthesized. Studies of monolayer properties are important to improve understanding of biological phenomena involving lipid/gemcitabine or lipid/gemcitabine-derivative interactions. The interfacial behavior of monolayers comprising DMPC, plus gemcitabine or lipophilic gemcitabine prodrugs at increasing molar fractions, was studied at the air/water interface at temperatures below (10 °C) and above (37 °C) the lipid phase transition. The effect of the hydrophobic chain length of gemcitabine derivatives on the isotherm of pure DMPC was investigated by surface tension measurement, and the results are reported as molar fractions, as a function of mean molecular area per molecule. The results show that the compounds interact with DMPC, producing mixed monolayers that are subject to an expansion effect, depending on the prodrug chain length. The results give useful information on the interaction of these prodrugs with biological membranes, and increase knowledge of the incorporation site of such compounds, as a function of their lipophilicity, in a lipid carrier; they may lead to improved liposomal formulation design.