Incorporation of acridine orange and methylene blue in Langmuir monolayers mimicking releasing nanostructures

• Published in: Biochimica et biophysica acta. Biomembranes 2023-06, Vol.1865 (5), p.184156-184156, Article 184156
• Main Authors: Pivetta, Thais P., Jochelavicius, Karen, Wrobel, Ellen C., Balogh, Debora T., Oliveira, Osvaldo N., Ribeiro, Paulo A., Raposo, Maria
• Format: Article
• Language: English
• Subjects: Acridine Orange; Langmuir; Liposomes; Methylene Blue; Mixed monolayers; Photosensitizer; Sodium Cholate; Spectrophotometry, Infrared
• ISSN: 0005-2736; 1879-2642
• DOI: 10.1016/j.bbamem.2023.184156

The efficiency of methylene blue (MB) and acridine orange (AO) for photodynamic therapy (PDT) is increased if encapsulated in liposomes. In this paper we determine the molecular-level interactions between MB or AO and mixed monolayers of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC), 1,2-dipalmitoyl-sn-glycero-3-phospho-(1′-rac-glycerol) (DPPG) and cholesterol (CHOL) using surface pressure isotherms and polarization-modulated infrared reflection absorption spectroscopy (PM-IRRAS). To increase liposome stability, the effects from adding the surfactants Span® 80 and sodium cholate were also studied. Both MB and AO induce an expansion in the mixed monolayer, but this expansion is less significant in the presence of either Span® 80 or sodium cholate. The action of AO and MB occurred via coupling with phosphate groups of DPPC or DPPG. However, the levels of chain ordering and hydration of carbonyl and phosphate in headgroups depended on the photosensitizer and on the presence of Span® 80 or sodium cholate. From the PM-IRRAS spectra, we inferred that incorporation of MB and AO increased hydration of the monolayer headgroup, except for the case of the monolayer containing sodium cholate. This variability in behaviour offers an opportunity to tune the incorporation of AO and MB into liposomes which could be exploited in the release necessary for PDT. [Display omitted] •AO and MB molecules contributes to an expansion of the mixed monolayer.•Hydration of carbonyl and phosphate groups of LM and LM+ Span® 80•Dehydration of lipid monolayers+ sodium cholate•Monolayer order is dependent on the photosensitizer and surfactant.•Suitability of incorporation of AO and MB in lipid nanostructures was confirmed.