Title: Oxidation of Langmuir-Blodgett films of monounsaturated lipids studied by atomic force microscopy

Authors: Ndeye Rokhaya Faye; Fabien Moroté; Christine Grauby-Heywang; Touria Cohen-Bouhacina

Addresses: Laboratoire Ondes et Matière d'Aquitaine (LOMA), UMR CNRS 5798, Université Bordeaux 1, 351 cours de la libération, 33405 Talence Cedex, France ' Laboratoire Ondes et Matière d'Aquitaine (LOMA), UMR CNRS 5798, Université Bordeaux 1, 351 cours de la libération, 33405 Talence Cedex, France ' Laboratoire Ondes et Matière d'Aquitaine (LOMA), UMR CNRS 5798, Université Bordeaux 1, 351 cours de la libération, 33405 Talence Cedex, France ' Laboratoire Ondes et Matière d'Aquitaine (LOMA), UMR CNRS 5798, Université Bordeaux 1, 351 cours de la libération, 33405 Talence Cedex, France

Abstract: In this work, we studied the stability in time of Langmuir-Blodgett films of POPC and OPPC, two unsaturated phospholipids with similar chains, differing by the relative position of these chains on the glycerol backbone. These films, transferred from the air-water interface onto freshly cleaved mica, were characterised by Atomic Force Microscopy (AFM) giving information on their topography at a lateral and perpendicular resolution in the nm range. AFM images (obtained in tapping mode) of freshly transferred films are homogenous, in agreement with the fact that these two lipids are in a liquid-expanded phase under our experimental conditions. After two days, small domains are observed, higher than the surrounding phase of about 0.8 nm in both types of samples. These domains are not observed if the samples are kept under vacuum, or if LB films are made of saturated phospholipids, suggesting that they are due to the local oxidation of POPC or OPPC, the oxidation being slightly more pronounced in the last case. Their dispersion in LB films suggests that oxidation occurs at different points at the same time, likely in areas presenting a loose packing or a defect. The local increase of thickness could be due to the reversal of the oxidised chain, raising the oxidised lipid above the surrounding phase.

Keywords: Langmuir-Blodgett films; unsaturated lipids; oxidation; atomic force microscopy; AFM; nanotechnology.

DOI: 10.1504/IJNT.2013.053511

International Journal of Nanotechnology, 2013 Vol.10 No.5/6/7, pp.390 - 403

Received: 08 May 2021
Accepted: 12 May 2021

Published online: 26 Apr 2013 *

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