# Has the Toxicity of Therapeutic Deep Eutectic Systems
## 2 Cell Lines
### Cell Viability
In general, some THEDESs show good properties when the bacterial toxicity is the objective, while the low cytotoxicity of the other exposed cell lines is maintained. A similar situation was found when amoebae was the focus of the antimicrobial activity of the THEDESs [58]. As cancer remains as a challenging disease for effective therapies, some THEDESs have also checked for this therapeutic application. [PERSON] et al. explored the possibility of including limonene within a THEDES while trying to decrease its intrinsic toxicity for normal cells. Mixtures of limonene with capric acid or menthol did not seem to decrease its toxicity, whereas combinations of limonene with ibuprofen (1:4) did. Moreover, a synergistic effect of this latter THEDES was found that overcomes the simple mixture of its individual components, as previously shown with the DES. Even a different mechanism of action is followed by the THEDESs compared to the isolated ibuprofen and limonene, but their advantages for cancer therapy are preserved [31]. Notably, in a review, [PERSON] et al. suggested to understand the cytotoxicity process of THEDESs when affecting different kinds of cell lines, malignant and non-malignant, in order to take advantage of this knowledge to design proper therapies for specific cancer types, such as colorectal cancer [59]. Later on, [PERSON] et al. evaluated the usefulness of different THEDES including terpen and nonsteroidal anti-inflammatory drugs. They found that a specific mixture containing menthol/ibuprofen (3:1) was selectively cytotoxic toward cancer cells [30]. In diabetes mellitus, chlorpropamide and tolbutamide were solubilized with tromethamine and a proportion of water after trying other conformers. In the study developed by [PERSON] et al., these THEDESs showed a low toxicity profile in two cell lines involving murine fibroblasts and human cancer cells [60]. The treatment of tuberculosis is another field where THEDESs are being analyzed. [PERSON] et al. combined citric acid with L-arginine or ethambutol, and the cytotoxicity was assessed using the Caco-2 cell line. Citric acid was found to be more toxic than ethambutol for this specific cell line. The acidity of the media was pointed out as a relevant factor that could increase the toxicity of THEDESs, as seen with previous studies with DESs [61]. In relation to the development of new drug delivery systems, [PERSON] et al. found that the cell proliferation of fibroblast was not inhibited by the exposure to gelatin fibers with encapsulated THEDESs composed of ChCl and mandelic acid. At the same time, fibers impregnated with THEDES maintained the expected antibacterial activity [38]. In another study, a liquid L-arginine-based THEDES was encapsulated in a lipidic matrix. When checking its cytotoxicity toward a mouse fibroblast cell line, no toxicity was found [62]. In addition, [PERSON] et al. explored the cytotoxicity profile of a THEDES including ibuprofen in the form of hydrogel for transdermal administration. The main action of the ibuprofen was maintained while arginine/glycerol (1:4) was used to solubilize it. Human abdominal skin samples were used to check the enhancement of drug permeation. Additionally, murine macrophages were analyzed in relation to the cytotoxicity, and no toxicity was found [55].