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Molecular insight into the barrier function of sebaceous and skin lipids and the interactions of lipid membranes with antimicrobial peptides and therapeutic nanoparticles

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Title: Molecular insight into the barrier function of sebaceous and skin lipids and the interactions of lipid membranes with antimicrobial peptides and therapeutic nanoparticles
Authors: Tascini, Anna Sofia
Item Type: Thesis or dissertation
Abstract: Sebaceous and skin lipids from the outermost layer of the epidermis, the stratum corneum (SC), play a vital role in regulating the hydration level of our skin. Skin lipids constitute the first layer of defence against toxic particles entering the body, and the first barrier to overcome when cosmetic and therapeutic creams are applied to the skin. This thesis gives insights into the properties of the skin surface at the microscopic level by introducing a model of the sebum, the oily layer covering the SC. Molecular dynamics simulations are used to investigate the structural and thermodynamic properties of the sebum in bulk and at air and water interfaces, and to study its interactions with water and SC lipids. The sebum model accurately reproduces experimental results, such as density, surface tensions and surface pressure-area isotherms. Calculating the free energy barrier to water penetration indicates that the sebum is permeable to water diffusion via a network of clustered triglyceride glycerol groups, suggesting that the sebum may play a significant role in the water regulation function of the skin. The model is also used to obtain a molecular understanding of SC lipid-sebum interactions. It is shown that sebum triglycerides interact strongly with epidermic lipids and extract them from the bilayer. Using microsecond simulations, the mechanisms associated with the extraction processes are identified and the corresponding free energies are quantified. Further, it is shown that the skin surface has a low affinity for water (contact angle: approximately 100 degree ), highlighting a striking difference between SC lipids and phospholipids. Heat transfer from a nanoparticle and the conformations of an antimicrobial peptide are also studied, with the eventual, future goal of combining these with the sebum-SC model. Finally, an outreach activity to improve the general public’s understanding of lipid molecules and their amphiphilic structure or “split-personality”, is described.
Content Version: Open Access
Issue Date: Jul-2018
Date Awarded: Dec-2018
URI: http://hdl.handle.net/10044/1/84743
DOI: https://doi.org/10.25560/84743
Copyright Statement: Creative Commons Attribution NonCommercial Licence
Supervisor: Bresme, Fernando
Seddon, John M.
Chen, Rongjun
Sponsor/Funder: European Union
Funder's Grant Number: 608184
Department: Chemistry
Publisher: Imperial College London
Qualification Level: Doctoral
Qualification Name: Doctor of Philosophy (PhD)
Appears in Collections:Chemistry PhD theses



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