New ionic liquids based on 5-fluorouracil: Tuning of BSA binding and cytotoxicity

In this work, we describe the synthesis, interactions with bovine serum albumin, and cytotoxicity of new ionic liquids based on 5-fluorouracil (API-ILs) with different cations (imidazolium, choline, isoquinolinium, guanidinium). The secondary and tertiary structure of BSA in solutions with different concentrations of API-ILs was monitored by the circular dichroism (CD) technique. The addition of API-ILs does not lead to structural changes in BSA. A quenching of fluorescence spectra intensity of BSA in presence of all API-ILs was observed, allowing the quantification of binding between API-ILs and BSA. The preferred localization of both ions in API-ILs differs significantly depending on the structure of the cation according to molecular docking. The aggregation of BSA in presence of API-ILs was analyzed by the dynamic light scattering (DLS) method, revealing a moderate increase in particle size. Cytotoxicity and selectivity of API-ILs on cancer and normal cell lines were estimated, showing a clear modification of the pharmaceutic activity of ionic liquid compared to 5-fluorouracil.