engleski

Tuning of surface free energy of supported mixed lipid monolayers for sensor applications

various novel sensors incorporating membrane based films. The surface free energy (SFE) of a lipid film significantly influences physicochemical processes occurring at the interface and its magnitude arises from the kind and strength of the involved intermolecular interactions. The functionalization of a mixed lipids film transferred onto a solid substrate and the performance of a sensor based on such film depends on SFE. On the other hand, SFE of a supported mixed lipid layer is influenced by several parameters of which the mixing ratio and type of the subphase used in the self- assembly of lipid layers and hydrophobicity of the supporting substrate are most important. Thus, a careful selection of these parameters enables tuning of the SFE of a supported lipid layer in order to achieve optimal sensor performance. The aim of this study was to assess the influence of mixing ratio and substrate type on SFE of the supported lipid layer. The SFE of supported self-assembled pure and mixed lipid layers was determined by using contact angle measurements in conjunction with Fowkes theory. The measurements of contact angles were conducted using four standard liquids (water, formamide, diiodomethane and ethylene glycol).The investigation comprehended 1- palmitoyl-2- oleoylphosphatidylcholine (POPC), and oleic acid triglyceride - triolein (TG). Pure and mixed lipid layers on solid substrates were formed by a transfer of the self assembled layer from a water subphase using the Langmuir-Blodgett / Schaefer techniques. The results show that much higher SFE, tunable in a wider range is obtained for layers on the hydrophilic than on the hydrophobic substrate. The results are interpreted in terms of the influence of the mixing ratio and intermolecular interactions on polar and disperse components of SFE and on film stability.

surface free energy ; lipid layer ; POPC ; triolein ; contact angle

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