Through attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), we have studied the adsorption characteristics of small unilamellar vesicles (SUVs) of a gel-phase phospholipid, dipalmitoylphosphatidylcholine (DPPC), on an oxidized gold substrate. By monitoring the frequencies and intensities of vibrational absorption modes due to phosphate and methylene functional groups in the head and tail regions of the phospholipid, we differentiated the adsorption state of the precursor vesicles (i.e., intact vs ruptured vesicles) as a function of vesicular size in the SUV limit and the properties of the aqueous-phase solvent. We found that on oxidized gold, vesicles of DPPC in ultra pure water remained intact for all sizes tested (viz., 65, 80, and 160 nm) with varying degree of deformation. In contrast, when phosphate-buffered saline (PBS) was used as a bathing medium, all vesicles remained intact, were more distorted than the same size in pure water, and appeared to be nearly fully collapsed. Taken together, these results provide a rough guide for controlling vesicular behavior at the oxidized gold surface.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Electronic, Optical and Magnetic Materials
- Surfaces, Coatings and Films