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Interaction of water-soluble surfactants with self-assembled lipid monolayers at the vapor-liquid interface: equilibrium and dynamic phenomena

Nigam, Poonam
http://rave.ohiolink.edu/etdc/view?acc_num=osu1157987838

Abstract Details

2006, Doctor of Philosophy, Ohio State University, Chemical Engineering.
The overall goal of the present research is to develop a better understanding of the penetration and interaction of amphiphilic additives into lipid monolayers. In the present work we have studied penetration of the anionic surfactant sodium dodecyl sulfate (SDS) and polymeric surfactant Pluronic F-68 into single lipid monolayers of two phosphatidylchololine membrane lipids, DPPC and POPC, and compare these results with the penetration into monolayers containing a mixture of two lipids i.e. DPPC and POPC, DPPC and cholesterol, and POPC and cholesterol. We have selected Pluronic F-68 and SDS for detailed studies because of their extensive current use in bioprocesses. Pluronic F-68 is the most widely used shear protectant surfactant in cell cultures. A series of isotherms were obtained by compressing mixed Pluronic F-68/lipid monolayers over subphase containing varying concentration of Pluronic F-68. Results obtained were analyzed by applying various thermodynamic theories to calculate the surface excess of Pluronic F-68 in the monolayer. By doing so, we also aim to prove the validity of these thermodynamic models by applying them to experimental data. We observed that Pluronic F-68 penetrates more into DPPC than POPC monolayers. Results indicate that Pluronic F-68 is completely excluded from the lipid monolayers at surface pressures ranging from 20 mN/m to 30 mN/m. We found that most of the theoretical models are able to predict the experimental observations fairly well. The methodology used for Pluronic F-68 was also applied to study the incorporation of SDS molecules into lipid membranes. Mixed monolayers of cholesterol with POPC suggest that the presence of cholesterol condenses the monolayer and hence reduces the extent of penetration. The most interesting behavior was observed with the mixed monolayer of DPPC and cholesterol, suggesting that addition of cholesterol to the monolayers result in a rigidifying effect at low surface pressures and a fluidizing effect at high surface pressures. Penetration dynamics of SDS in cholesterol-lipid mixed monolayers confirmed this observation. Further, we found that penetration in the monolayer decreases with increasing cholesterol/phospholipids ratio until a minimum is reached, beyond which increasing the cholesterol/phospholipids ratio results in an increase in the penetration.
James Rathman (Advisor)
189 p.
Engineering, Chemical
Pluronic F-68; Sodium Dodecyl Sulfate (SDS); Langmuir Monolayers; Pethica's Equation; Modified Motomura's Equation

Recommended Citations

Citations

  • Nigam, P. (2006). Interaction of water-soluble surfactants with self-assembled lipid monolayers at the vapor-liquid interface: equilibrium and dynamic phenomena [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1157987838

    APA Style (7th edition)

  • Nigam, Poonam. Interaction of water-soluble surfactants with self-assembled lipid monolayers at the vapor-liquid interface: equilibrium and dynamic phenomena. 2006. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1157987838.

    MLA Style (8th edition)

  • Nigam, Poonam. "Interaction of water-soluble surfactants with self-assembled lipid monolayers at the vapor-liquid interface: equilibrium and dynamic phenomena." Doctoral dissertation, Ohio State University, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=osu1157987838

    Chicago Manual of Style (17th edition)

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© 2006, all rights reserved.
This open access ETD is published by The Ohio State University and OhioLINK.