Evidence of photoinduced lipid hydroperoxidation in Langmuir monolayers containing Eosin Y

Abstract

Photodynamic therapy (PDT) efficiency depends on many factors including the incorporation of the photosensitizer (PS) in cell membranes and possible lipid hydroperoxidation. In this study, we show that hydroperoxidation may be photoinduced when eosin Y is incorporated into Langmuir monolayers that serve as cell membrane models. This occurs for Langmuir monolayers of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) and 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC), which have unsaturation in their hydrophobic chains. In contrast, light irradiation had no effect on monolayers of saturated 1,2-dipalmitoyl-sn-glycero-3phosphocholine (DPPC). Evidence of hydroperoxidation was obtained from the area increase in eosin-containing DOPC and POPC monolayers upon irradiation, which was accompanied by a decrease in monolayer thickness according to grazing incidence X-ray off-specular scattering (GIXOS) data. Furthermore, the changes in polarization-modulated infrared reflection absorption spectroscopy (PM-IRRAS) induced by irradiation were consistent with hydroperoxide migration toward the lipid hydrophilic heads.. In summary, this combination of experimental methods allowed us to determine the effects of eosin Y interaction with cell membrane models under irradiation, which may be associated with the underlying mechanisms of eosin Y as photosensitizer in PDT.

Photochemical aging of atmospherically reactive organic compounds involving brown carbon at the air–aqueous interface

“…This trend continued up to a point where the DOPC molecules were packed closely and have very little space to move. Finally, the DOPC monolayer collapsed at 46 mN m −1 (Pereira et al, 2018). Applying an increasing 9892 S. Li et al: Photochemical aging of atmospherically reactive organic compounds pressure at the collapse pressure caused the monolayer to become unstable and destroy the monolayer.…”

“…These photosensitized reactions have been shown in the laboratory to induce to an abiotic source of volatile organic compounds (VOCs) and secondary organic aerosols (SOA) in the marine boundary layer (Rossignol et al, 2016;Tinel et al, 2016;Bernard et al, 2016). Traces of photosensitizing species in the aerosol phase, such as imidazoles, quinones and nitrophenols also contribute to SOA formation through their promoting effect with radical reactions (Li et al, 2016;Desyaterik et al, 2013;Pillar and Guzman, 2017).…”

Photochemical aging of atmospherically reactive organic compounds involving brown carbon at the air-aqueous interface

“…This caused condensation and ordering at the interface, increasing the surface pressure of the organic monolayer. Finally, the DOPC monolayer collapsed at 46 mN/m (Pereira et al, 2018). The π−A isotherms of the DOPC monolayers were shifted to larger molecular areas upon the introduction of the photosensitizing molecules into the bulk artificial seawater.…”

“…The slow oxidation of DSPC molecules at the air-sea water interface in the ambient environment does not produce sufficient surface-active molecules, leading to the loss of DSPC molecules from the surface. Previous irradiation studies suggest that green light (530 nm) induced little loss in the surface area of saturated 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) monolayer mixed with photosensitive erythrosine or eosin Y molecules (Pereira et al, 2018;Aoki et al, 2016). When considering the liposomal binary mixture of phospholipids containing 1,2-bis(10,12-tricosadiynoyl)-sn-glycero-3-phosphocholine (DC 8,9 PC) and DPPC, DC 8,9 PC can produce intermolecular cross-linking following the release of 5,6-carboxyfluorescein dye under UV irradiation.…”

“…Unsaturated lipids are more susceptible to the attack of 1 O 2 and free radicals. Reactions of 1 O 2 with unsaturated bonds in lipid chains can generate hydroperoxide (OOH) groups and then increase molecular area of lipid monolayer due to hydrophilic-hydrophobic balance of the modified chain (Caetano et al, 2007;Riske et al, 2009;Aoki et al, 2016;Pereira et al, 2018). The hydroperoxide group in DOPC is more water soluble than the aliphatic chain of DOPC ( Fig.…”