*3.6. Cytotoxicity Studies*

In vitro cytotoxicity tests in the HCT116 cell line were performed in PZQ, SEP, VHS, PZQ–SEPet and PZQ–VHSet products. The interaction products with ethanol were selected as a reference from the rest because they present an increase in the in vitro dissolution profile in sink conditions and in non-sink conditions, as demonstrated by previous work [33].

The raw material (PZQ, SEP and VHS) in concentrations between 6.4 nM and 100 μM were tested, demonstrating that they can be considered biocompatible toward HCT116 cell lines due to the fact that the percentage of the cell viability was slightly lower than the untreated cells in all cases (control) (Figure 6).

**Figure 6.** Cell viability of SEP and PZQ–SEPet (**a**), and VHS and PZQ–VHSet (**b**) compared to PZQ after 48 h of treatment. (Control: untreated cells in complete medium; mean values ± 8 SE; *n* = 3).

In the PZQ–SEPet interaction products, the loss of cell viability was not observed in any of the concentrations tested, even a positive effect in cell growth was observed with respect to the control, and pure SEP and PZQ. Therefore, the PZQ–SEPet revealed its biocompatibility with cell and had a positive effect on the cell viability compared to raw PZQ and SEP solids in these ranges of concentrations (Figure 6a). PZQ–SEPdic and PZQ–SEPac products are expected to behave similarly.

PZQ–VHSet showed a slight loss of cell viability like pure products, up to a maximum of 11% in the highest concentration tested. In this case, a positive effect on cell growth was not observed, but the viability of the PZQ–VHSet interaction product was similar to that of the pristine drug and VHS, therefore it can be considered biocompatible according to the in vitro results (Figure 6b). Likewise, PZQ–VHSdic and PZQ–VHSac products are expected to have similar behavior.
