Abstract
The interaction of the antibacterial polymer–branched poly(ethylene imine) substituted with quaternary ammonium groups, PEO and alkyl chains, PEI25QI5J5A815–with a solid supported lipid bilayer was investigated using surface sensitive optical waveguide spectroscopy. The analysis of the optogeometrical parameters was extended developing a new composite layer model in which the structural and optical anisotropy of the molecular layers was taken into consideration. Following in situ the change of optical birefringence we were able to determine the composition of the lipid/polymer surface layer as well as the displacement of lipid bilayer by the antibacterial polymer without using additional labeling. Comparative assessment of the data of layer thickness and optical anisotropy helps to reveal the molecular mechanism of antibacterial effect of the polymer investigated.
Highlights
Cell walls or membranes control the chemical communication between otherwise isolated compartments in the living organisms
Effect of antibacterial polymer on the supported lipid bilayer was studied by the OWLS technique
As an extension of the analysis of the parameters determined by OWLS technique the optical birefringence of the ordered molecular layer is deduced
Summary
Cell walls or membranes control the chemical communication between otherwise isolated compartments in the living organisms. The waveguide spectroscopy techniques as dual polarization interferometry (DPI) [40,41], coupled plasmon waveguide resonance (CPWR) [42,43], and optical waveguide lightmode spectroscopy (OWLS) [44,45,46,47,48,49,50,51] are especially valuable among those because of the possibility to deduce the presence and integrity of the bilayer, which is a crucial functional property [10]. In the present work branched PEI functionalized with cationic groups, as well as hydrophilic and alkyl chains, PEI25QI5J5A815 [20], was used to determine its interaction and exchange with solid supported lipid, POPC, bilayers applying the OWLS technique. The fluid flow provides a constant concentration profile during the measurement thereby the condition resembles to the bacterial contact with a permanent antibacterial coating
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