Membrane remodeling induced by lipid photo-oxidation

We investigated how lipid photo-oxidation can affect plasma membrane models represented by giant unilamellar vesicles (GUVs). Here, we compare the effect of two photo-activated photosensitizers (PS), methylene blue (MB) and DO15, upon lipid bilayers containing POPC:DPPC:Cholesterol (Chol) compared to those containing a hydroperoxide lipid POPC-OOH:DPPC:cholesterol. Changes in lipid composition were explored. The photosensitizers were selected because MB is a hydrophilic molecule, therefore it is preferentially located in the aqueous medium close to the membrane, while DO15 is more hydrophobic than MB, therefore it is preferentially located in the lipid bilayer. The mechanisms of lipid photo-oxidation may be different due to different PS location. This will be also here explored. It is interesting to highlight that depending on the lipid molar ratio, the effects observed using phase contrast and fluorescence microscopy were different. The results obtained in some cases indicated changes in the liquid-ordered (Lo) - liquid- disordered (Ld) phase separation of the membranes and the appearance of micro pores.