Colloidal formulations of etoposide based on self-assembling oleyl-hyaluronan-based structures: optimization of technology and in vitro analysis

The ability of the conjugate of hyaluronic acid and oleic acid (oleyl hyaluronan — HA-C18:1) to form self-assembling micellar structures was utilized to enhance the water solubility of the anticancer drug etoposide (ETP) and its prodrug, 4-O′-benzyloxycarbonyl derivative (ETP-Cbz). Using density functional theory (DFT), it was established that the ETP-Cbz associate with HA-C18:1 had greater thermodynamic stability compared to the ETP associate, which was confirmed experimentally. The micelles loaded with ETP-Cbz were smaller (268 nm compared to 407 nm), more stable (with the critical micelle concentration (CMC) decreasing from 0.07 to 0.025 mg/mL), and had the higher drug loading efficiency (82 %) as compared to HA-C18:1/ETP micelles. In vitro experiments showed that both micellar formulations exhibited low hemolytic activity and delayed drug release profiles during the first hours. In vitro cytotoxicity against MCF-7 and MDA-MB-231 cell lines showed the dose-dependent decrease in cell viability whereas the toxic effect against normal human dermal fibroblasts (NHDF) was significantly lower and exceeded the concentration of HA-C18:1 in the micellar formulations. Confocal microscopy was used to confirm the active uptake of micellar formulations by MDA-MB-231 cells. These findings, therefore, suggest that HA-C18:1 may be a promising solubilizing agent for etoposide and its prodrug.