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Surface free energy of self-assembled pure and mixed lipid layers

The supported lipid mono and bilayers are widespread tool for mimicking the structure and functions of biomembranes. Lipid layers are also used as sensor element host in development of various novel sensors incorporating membrane based films. The surface free energy (SFE) of lipid films plays a crucial role in physicochemical processes occurring at the interface and its magnitude arises from the kind and strength of involved intermolecular interactions [1, 2]. The surface free energy of solid supported self-assembled pure and mixed lipid layers was studied using contact angle measurements in conjunction with Fowkes and Owens-Wendt- Rabel-Kaelble (OWRK) theories [3]. The measurements of contact angles were conducted using four standard liquids (water, formamide, diiodomethane and ethylene glycol).The investigation comprehended 1, 2- dioleoyl-sn-glycero-3-phosphocholine (DOPC) , 1-Palmitoyl-2-oleoylphosphatidylcholine (POPC), and oleic acid triglyceride - triolein (TO). Pure and mixed lipid mono and bi-layers on solid substrates were formed by spontaneous spreading and by transfer of the self assembled monolayer from a subphase of 0.55 M NaCl water solution using the Langmuir–Blodgett / Schaefer techniques. The results of SFE determination of the investigated mixed and single lipid layers on hydrophilic and hydrophobic substrates are presented and discussed in terms of influence of the mixing ratio on the intermolecular interactions and film stability. [1] C. A. Keller, K. Glasmastar, V. P. Zhdanov, B. Kasemo, . Phys. Rev. Lett. 84 (2000) 5443- 5446. [2]. V. I. Silin et al. J. Am. Chem. Soc. 124, 2002 14676-14683. [3] D. K. Owens, R. C. Wendt, J. Appl. Polym. Sci., 13 (1969) 1741-1747.

Surface free energy; lipid layer; Langmuir-Blodget; DOPC; POPC

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