The surface behavior of mixed monolayers and LB films of betulin-containing polymers with lipids at the air-Ce³⁺ aqueous solution interface and on solid substrate

The formation and surface behavior of mixed monolayers and LB films of two betulin methacrylate-containing polymers with molar fraction of betulin methacrylate equal to 10% (Bet-1) and 15% (Bet-2) with lipids—cholesterol and dihexadecyl phosphate (DHP), were investigated at the Ce³⁺ aqueous subphase and on silicon support using Langmuir techniques, AFM and wettability. The comparison of mixed polymer-lipid monolayers with homogeneous polymers ones and assessment of hydrophilicity by the rate of capillary rise of water along polymer films impregnated into porous cellulose showed stronger interaction of Bet-2 with water in comparison with Bet-1. The data of surface pressure–area isotherms of mixed monolayers (Bet-1-Chol, Bet-2-Chol, Bet-1-DHP and Bet-2-DHP) at the water and Ce³⁺-containing subphase demonstrate the liquid-expanded (LE)—liquid-condensed (LC) phase transition in all cases of π near 15–20 mN/m regardless subphase nature and monolayers components. The mean molecular area A₀ calculated by lipid of LC phase decreased by 1.5–2.0 times in comparison with A₀ of LE phase after phase transition with chess or two layers structures with the exception of Bet-2-DHP monolayers on water where betulin fragments of polymer immobilized into monolayers, and A₀ increased up to 3 times. AFM and wettability data of polymer-lipid LB films showed effect of Ce³⁺ ions on their morphology and characterize Ce³⁺ immobilization into monolayers. We showed good viability of Bet-1, Bet-2 and their combinations with Ce³⁺ using MTT test. Therefore, Ce³⁺-containing polymer-lipid systems can be used for the design of new hybrid polymer-lipid components for drug delivery.