Schematic representation of the combined four detector reflectometry and QCM-D setup. Compared to the conventional reflectometric setup (solid lines), the four detector design also measures the reflection of an additional beam (dashed lines). L—laser, PZ—polarizer, SS—sensor surface, P—prism, PB—polarizing beamsplitter, and PD—photodetector.
An optical model representing the four detector reflectometry system. P—prism, AL—adlayer, BS—the bulk solution media, and SS—the sensor surface. The transmittance and the reflectance are denoted by and , and the intensities of the first and second beams are denoted by and .
Bilayer formation via vesicle fusion on silica recorded by QCM-D ( and ) and reflectometry. The shifts in (-○-) and (-◻-) shown are for the fifth overtone . Additional harmonics gave qualitatively similar results and are omitted for clarity. Reflectometric data recorded using a conventional setup (-△-) and corrected for binding of material to the surface of the prism (-◇-) (four detector setup) both are shown for comparison.
Reflectometric responses obtained upon exposure of a bare (-◻-) and a PLL-g-PEG coated silica surface (-○-) to POPC vesicles. The net response, i.e., the difference between the two contributions, is also shown (-△-).
Time-resolved variation of the acoustic mass (-○-), the lipid molecular mass (-△-), and the solvent mass (-◻-), as determined with the combined setup, for the formation of a supported lipid bilayer on a silica surface upon exposure to POPC vesicles.
Dependence of film hydration (in percentage of the acoustic mass) on the optical mass for the formation of a lipid bilayer on a silica surface.
Time-resolved refractive index (-○-) and thickness (-◻-) of the lipid layer adsorbed on silica surface during a bilayer formation.
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