Insertion Mechanism of a Poly(ethylene oxide)-poly(butylene oxide) Block Copolymer into a DPPC Monolayer

Abstract

Interactions between amphiphilic block copolymers and lipids are of medical interest for applications such as drug delivery and the restoration of damaged cell membranes. A series of monodisperse poly(ethylene oxide)-poly(butylene oxide) (EOBO) block copolymers were obtained with two ratios of hydrophilic/hydrophobic block lengths. We have explored the surface activity of EOBO at a clean interface and under 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) monolayers as a simple cell membrane model. At the same subphase concentration, EOBO achieved higher equilibrium surface pressures under DPPC compared to a bare interface, and the surface activity was improved with longer poly(butylene oxide) blocks. Further investigation of the DPPC/EOBO monolayers showed that combined films exhibited similar surface rheology compared to pure DPPC at the same surface pressures. DPPC/EOBO phase separation was observed in fluorescently doped monolayers, and within the liquid-expanded liquid-condensed coexistence region for DPPC, EOBO did not drastically alter the liquid-condensed domain shapes. Grazing incidence X-ray diffraction (GIXD) and X-ray reflectivity (XRR) quantitatively confirmed that the lattice spacings and tilt of DPPC in lipid-rich regions of the monolayer were nearly equivalent to those of a pure DPPC monolayer at the same surface pressures.

Interfacial Properties in Langmuir Monolayers and LB Films of DPPC with Partially Fluorinated Alcohol (F8H7OH)

“…The FM images of the DPPC monolayers the first column indicated the coexistence of the LE and LC phases. The shape of the LC domain is characteristic of DPPC monolayers and has been discussed previously 20,21,39,40 . At X F8H7OH 0.05, there were few differences in the domain shapes as determined from the images of the DPPC monolayer.…”

Two-Component Langmuir Monolayers and LB Films of DPPC with Partially Fluorinated Alcohol (F8H9OH)

“…In fact, the FM image of DPPC monolayers the first column is clearer in contrast compared to the BAM image. The shape of the LC domain is characteristic of DPPC monolayers, which has been discussed well 11,12,35,36 .…”

3-Hydroxybutyric Acid Interacts with Lipid Monolayers at Concentrations That Impair Consciousness

“…For example, amphiphilic block copolymers, such as poloxamers, incorporate into DPPC monolayers but remain in a separate, distinct phase from DPPC, resulting in inhomogeneous monolayers. 26,29 At all concentrations studied, with increasing BHB concentration, there was an increase in the mean molecular area at which the surface pressure rose above baseline (liftoff, Figure 1a). There was also a marked difference in compressibility of the monolayer when BHB was present, even at relatively low concentrations that are produced by the ketogenic diets that are used to treat seizures 30,31 (Figure 2).…”

“…In contrast, previous studies on the interaction between DPPC monolayers and macromolecules (polyethylene oxide−polybutylene oxide block copolymers) showed that, at surface pressure above 8 mN/m, DPPC and the copolymer phase separate, exhibiting an inhomogenous monolayer with two types of domains differing in shape and sizes. 26 The interfacial rheology for the DPPC monolayers as measured by ISR is presented in Figure 6. At surface pressures below 10 mN/m, the rheological properties were below the sensitivity level of the instrument.…”