Chitosan hybrid nanomaterials: A study on interaction with biomimetic membranes

This study examined the influence of nanomaterials (NMs) on the organization of membrane lipids and the resulting morphological changes. The cell plasma membrane is heterogeneous, featuring specialized lipid domains in the liquid-ordered (L_o) phase surrounded by regions in the liquid-disordered (L_d) phase. We utilized model membranes composed of various lipids and lipid mixtures in different phase states to investigate the interactions between the NMs and membrane lipids. Specifically, we explored the interactions of pure chitosan (CS) and CS-modified nanocomposites (NCs) with ZnO, CuO, and SiO₂ with four lipid mixtures: egg-phosphatidylcholine (EggPC), egg-sphingomyelin/cholesterol (EggSM/Chol), EggPC/Chol, and EggPC/EggSM/Chol, which represent the coexistence of L_d, L_o, and L_d/L_o, respectively. The data show that CS NMs increase the membrane lipid order at glycerol level probed by Laurdan spectroscopy. Additionally, the interaction of CS-based NMs with membranes leads to an increase in bending elasticity modulus, zeta potential, and vesicle size. The lipid order changes are most significant in the highly fluid L_d phase, followed by the L_o/L_d coexistence phase, and are less pronounced in the tightly packed L_o phase. CS NMs induced egg PC vesicle adhesion, fusion, and shrinking. In heterogeneous L_o/L_d membranes, inward invaginations and vesicle shrinking via the L_d phase were observed. These findings highlight mechanisms involved in CS NM-lipid interactions in membranes that mimic plasma membrane heterogeneity.