Langmuir Monolayer of Artificial Pulmonary Surfactant Mixtures with an Amphiphilic Peptide at the Air/Water Interface:  Comparison of New Preparations with Surfacten (Surfactant TA)

Abstract

Interfacial behavior was studied on the pulmonary lipid mixture containing a newly designed amphiphilic alpha-helical peptide (Hel 13-5) that consists of 13 hydrophobic and 5 hydrophilic amino acid residues. Moreover, the data obtained were compared with those of commercially available Surfacten (Surfactant TA) which has been clinically used for neonatal respiratory distress syndrome (NRDS) in Japan. Surface pressure (pi)-A and surface potential (DeltaV)-area (A) isotherms were measured for our synthetic preparations and Surfacten. Herein, a mixture of dipalmitoylphosphatidylcholine (DPPC)/egg-phosphatidylglycerol (PG)/palmitic acid (PA) (68:22:9 by weight) was used as the constituent of basic preparations. Monolayers were spread on 0.02 M Tris buffer (pH 7.4) with 0.13 M NaCl at the air/liquid interface, and the surface behavior was investigated by employing the Wilhelmy method, an ionizing electrode method, and fluorescence microscopy (FM). Cyclic compression and expansion isotherms of the prepared materials (or products) (DPPC/PG/PA/Hel 13-5) were examined to confirm the spreading and respreading ability. For the prepared products, a plateau region exists on pi-A and DeltaV-A isotherms at approximately 42 mN m(-1), indicating that Hel 13-5 is squeezed out of surface monolayers together with fluid components (PG) upon lateral compression. That is, the squeeze-out phenomenon induces a 2D-3D phase transformation. In particular, the inclination of the pi-A isotherms at X(Hel 13-5) = 0.1 in the plateau region was almost zero irrespective of the molecular area. As proposed in the earlier report (Nakahara, H.; Lee, S.; Sugihara, G.; Shibata, O. Langmuir 2006, 22, 5792-5803), an observed refluorescence phenomenon was discussed for FM measurements. This phenomenon provides evidence of the squeeze-out motion with fluid molecules. Furthermore, the cyclic pi-A and DeltaV-A isotherms show larger hysteresis areas and better respreading abilities in comparison with the previous ternary systems (DPPC/PG/Hel 13-5 and DPPC/PA/Hel 13-5) that are very important properties in pulmonary functions. FM photographs and the temperature dependence of pi-A and DeltaV-A isotherms suggest that the phase behavior of the present preparation product is very similar to that of Surfacten in terms of the domain size and in parameters such as collapse pressures, maximum DeltaV values, and so on. These results demonstrate that PG and PA even in the present preparations work well for compression-expansion cycling as is the case in the previous ternary systems, and the present preparations show comparable properties to Surfacten in vitro.

Miscibility behavior of two-component monolayers at the air–water interface: Perfluorocarboxylic acids and DMPE

“…The surface pressure (p) of monolayers was measured using an automated homemade Wilhelmy balance, which was the same as that used in the previous studies [20,26,34]. The surface-pressure balance (AG-245; Mettler Toledo, Greifensee, Switzerland) had a resolution of 0.01 mN m À1 .…”

Surface tension and adsorption behavior of mixtures of diacyl glycerol arginine-based surfactants with DPPC and DMPC phospholipids

“…Physicochemical interactions of water-insoluble phospholipid components of cell membranes with soluble or sparingly soluble surfactants in solutions, in dispersions, or at surfaces have been reported [19][20][21][22][23][24][25]. Understanding the behavior of model mixed monolayers may help understanding of more complex biological membranes.…”

Effects of Cardiolipin on Membrane Morphology: A Langmuir Monolayer Study

“…Differences in the dye solubility between the LE and the LC phases result in a contrast; the dark region contains tightly packed lipids in the LC phase. The dye is excluded from this solidlike phase and is localized in the loosely packed lipids in the LE phase surrounding the LC domains (32). The solid domains of DPPC started to appear when p coincided with the onset pressure for the LE-LC transition.…”