Miscibility in Binary Monolayers of Phospholipids and Linker Lipid

Abstract

We studied the miscibility in binary lipid matrixes made by the Langmuir−Blodgett (LB) technique. The components in the lipid matrix were N-(ε-maleimidocaproyl)-dipalmitoyl phosphatidylethanolamine (DPPE-EMC; biofunctionalized linker lipid) and a phospholipid. Three different matrix phospholipids were used: 1,2-dipalmitoyl-sn-glycero-3-phosphatidylethanolamine (DPPE), 1,2-dimyristoyl-sn-glycero-3-phosphatidylethanolamine (DMPE), and 1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine (DPPC). The phase-transition temperature of the linker lipid as determined by Fourier transform infrared spectroscopy was 45 °C. The surface potential of the linker lipid, 290 mV at pH 6.8, was clearly smaller than the values observed for pure phospholipids. Clear evidence of the miscibility could not be obtained from the surface pressure−area isotherms. On the contrary, Brewster angle microscopy (BAM) enabled a visual investigation of the miscibility and domain morphology. The best miscibility was obtained for DPPC/DPPE-EMC matrixes but only to some extent for DPPE/DPPE-EMC and DMPE/DPPE-EMC matrixes. Atomic force microscopy on solid supported LB films showed domains similar to the BAM images of Langmuir monolayers.

Temperature dependence of the organization and molecular interactions within phospholipid/diacetylene Langmuir films

“…Deciphering the organization and interactions of multicomponent Langmuir films is an active field of research [1][2][3][4][5]. The interactions and organization of two molecular components occupying the same two-dimensional space have been explored by thermodynamic [6,7] and microscopic [2,[8][9][10] approaches.…”

Biocomposite films synthesized at a fluid/fluid interface

“…When adsorbed at fluid/fluid interfaces, monolayers composed of mixtures of different PEs containing saturated or unsaturated acyl chains with various lengths often exhibit interesting two-dimensional patterns. [1][2][3] For example, mixtures of DOPE (1,2-dioleoyl-sn-glycero-3-phosphoethanolamine) and DPPE (1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine) form heterogeneous monolayers that exhibit distinct DOPE-rich and DPPE-rich domains. 2 Langmuir-Blodgett (LB) technology provides a way to transfer a self-assembled monolayer from an air/liquid interface onto a solid surface.…”

Miscibility of Lipids in Monolayers Investigated through Adsorption Studies of Antibodies

“…The unfavorable orientation of the biofunctional groups in the monolayer may decrease the reactivity of the surface toward the desired protein . Miscibility and phase behavior in floating Langmuir films can be detected by, e.g., Brewster angle microscopy (BAM) and in LB/LS films on solid substrates by scanning probe microscopy (SPM), especially by, e.g., using phase-contrast imaging in tapping mode. − However, the visual investigation of the miscibility with these methods is quite difficult, especially when the linker concentration is very low. Also, it is possible to study the miscibility of the binary monolayers with surface pressure isotherms, surface phase rule, and excess area criterion, but with these methods it is often difficult to make a clear distinction between complete miscibility and immiscibility. ,− …”

“…The unfavorable orientation of the biofunctional groups in the monolayer may decrease the reactivity of the surface toward the desired protein. 17 Miscibility and phase behavior in floating Langmuir films can be detected by, e.g., Brewster angle microscopy (BAM) 18 and in LB/LS films on solid substrates by scanning probe microscopy (SPM), especially by, e.g., using phase-contrast imaging in tapping mode. [19][20][21] However, the visual investigation of the miscibility with these methods is quite difficult, especially when the linker concentration is very low.…”

“…Also, it is possible to study the miscibility of the binary monolayers with surface pressure isotherms, surface phase rule, and excess area criterion, but with these methods it is often difficult to make a clear distinction between complete miscibility and immiscibility. 18,[22][23][24] Covalent coupling of pepsin-cleaved antibody Fab' fragments via a thiol-disulfide interchange reaction to 1,2-dipalmitoyl-sn-glycero-3-phosphoglycolipoate (DP-PGL) embedded in a host monolayer matrix of 1-palmitoyl-2-(16-(S-methyldithio)hexadecanoyl)-sn-glycero-3-phosphocholine (DSDPPC) has been recently demonstrated. 16 The excess area criterion was tested for this binary system, but it did not fully explain the miscibility or immiscibility of the components in the monolayers.…”