Viscoelasticity of Poly(ethylene glycol) Solutions on Supported Lipid Bilayers via Quartz Crystal Microbalance with Dissipation

Abstract

Supported lipid bilayers of 1,2-dioleoyl-sn-glycero-3-phosphocholine were formed on a silicon oxide substrate, and the viscoelasticity of poly(ethylene glycol) (PEG) solutions above the bilayer was subsequently studied by quartz crystal microbalance with dissipation monitoring. No detectable adsorption of PEG molecules to the bilayer was found over a broad range of PEG molecular weight at various concentrations. The viscoelastic properties of the PEG solutions were obtained from the shifts in the resonance frequency and the energy dissipation factor of the polymer solution in contact with the resonator-supported lipid bilayer. The resulting viscoelastic properties of PEG solutions were found to be in excellent agreement with the Zimm model for linear polymer chains in a good solvent. The excluded volume scaling exponent ν for PEG in water shows an ideal-to-real crossover with increasing molecular weight. The exponent adopts a value of 0.50 for short chains and gradually increases to 0.565 for long chains. The onset of the excluded volume effect of PEG in water, a good solvent, lies in the molecular weight range between 4000 and 8000.