In this work, we investigate the effect of chitosan hydrophobization on the internalization and cytotoxic effect of chitosan-based nanoparticles (NPs) on breast cancer cells (MDA-MB-231), cervical cancer cells (HeLa) and noncancer cells (Arpe-19). We also analyzed the interaction of NPs with a phospholipid (DPPC) membrane model at the airwater interface. An alkylation procedure to insert 8 carbon chains along the chitosan macromolecule with final 10 and 30 % substitution degrees was used. Nuclear magnetic resonance (NMR) and infrared spectroscopes (IR) were used to evaluate the success and extent of the hydrophobization procedure. Size, shape, and charge of NPs were evaluated by dynamic light scattering (DLS), atomic force microscope (AFM), and zeta potential, respectively. The effect of hydrophobicity on NPs was the reduction of the NPs average size, the formation of slightly elongated structures and the enhancing of the interaction of NPs with a DPPC monolayer at the air-water interface. By using fluorescence images on fluorescein-chitosan NPs, we observed a higher internalization of hydrophobic chitosan NPs in cancer cells in comparison with a low internalization of these NPs in normal cells. Even when non modified chitosan NPs were highly internalized in all cell lines, hydrophobized chitosan NPs showed a significantly higher cytotoxic effect on cancer cells in comparison with a lower effect showed by non-modified chitosan NPs on these cells. The cytotoxic effect on the normal cell line used was low for native chitosan NPs and negligible for hydrophobized chitosan NPs.
Keywords: Chitosan, hydrophobization, chitosan nanoparticles, cytotoxicity, cellular uptake, langmuir monolayers.