The interaction of serum albumin with cholesterol containing lipid vesicles

In this paper, the interaction of both human blood serum (the primary fraction of which is serum albumin) and pure human serum albumin (HSA) with surface immobilised lipid vesicles was measured by combined Surface Plasmon Resonance (SPR) and Surface Plasmon enhanced Fluorescence (SPEFS), and fluorescence microscopy. It was found that both blood serum and HSA showed specific binding to vesicles which contained cholesterol, resulting in increased membrane permeability and release of encapsulated fluorescent dye. This effect was not seen with heat inactivated blood serum, heat inactivated HSA or in vesicles not containing cholesterol. These results suggest that HSA may have a physiological role over and beyond that of fatty acid carrier, possibly acting to regulate vascular endothelial cell cholesterol concentration.