Cytotoxicity profile of choline chloride-malonic acid DES on normal human fibroblast cells

Deep eutectic solvents (DES) are gaining increasing attention as biocompatible alternatives to conventional organic solvents. In recent years, their possible application as drug delivery systems has been extensively explored, especially for enhanced drug solubility and bioavailability. Previous studies indicated that DES composed of choline chloride (ChCl), as a hydrogen bond acceptor, and organic acids, as hydrogen bond donors, such as malonic acid, could possess beneficial biological effects, but also cytotoxic activity; however, research regarding their effects on normal cells remains limited. In this work, we aimed to analyze the cytotoxic profile of DES composed of choline chloride and malonic acid (ChCl:Mal), on the human fibroblast cell line (MRC-5). ChCl:Mal was formulated in 1:1 molar ratio, and Fourier Transform Infrared Spectroscopy (FTIR) analysis was performed for DES characterization. The analysis of FTIR spectra confirmed the successful synthesis of DES. Cytotoxicity of the obtained DES was evaluated using XTT viability assay, in a concentration range of 0.1–4 mg/mL. The results showed that lower concentrations (0.1–0.8 mg/mL) exert a stimulatory effect on cell proliferation, seen as increased cell viability compared to the untreated control, indicating their good compatibility with cellular systems. On the contrary, higher concentrations of 1–2 mg/mL induced minor cell viability reduction, while a significant cytotoxic effect was detected at the concentration of 4 mg/mL, outlining cytotoxicity of higher concentrations. The results of the present study indicate that ChCl:Mal has promising potential as a novel green solvent system for biomedical applications, with favorable biocompatibility at concentrations up to 2 mg/mL.