Adsorption of high density lipoproteins (HDL) on solid surfaces

The adsorption of high density lipoproteins (HDL) on polyethylene (PE), poly(2-hydroxyethyl methacrylate) (poly(HEMA)), polyesterurethane (PU), Biomer, and mica surfaces was studied. The adsorption of HDL from a single protein solution and a plasma solution on the surfaces showed that the amount of adsorbed HDL was not related to the hydrophobicity (or hydrophilicity) of the surfaces. It was observed that the amount of HDL adsorbed on PE increased with increasing HDL concentration of a single protein solution until 5 mu g/ml, and increasing plasma concentration resulted in an increase of HDL adsorption. In addition, HDL adsorption from an HDL solution of 500 mu g/ml on PE reached a maximum within a few minutes at 25 degrees C. Only a propertion of adsorbed HDL could be desorbed when the adsorbed layers were incubated with Tween 20 or sodium dodecyl sulfate (SDS), while the desorption was dependent on the nature of the surfaces. It was more difficult to desorb HDL adsorbed from plasma to PE than to desorb HDL adsorbed from a single protein solution to PE. It was found that the desorption of adsorbed HDL from PE by the detergents was decreased if the protein layer had been stored in buffer (pH 7.4) for 24 h before desorption, while a higher storing temperature had a negative effect on the desorption of the lipoprotein from the surface. Adsorbed HDL on mica in a physiological buffer was imaged by a tapping mode atomic force microscope (AFM). The surface appeared to be covered by single HDL proteins as well as clusters of two or three HDL proteins with an average height of 5 to 6 nm. Furthermore, the partial desorption of adsorbed HDL from mica was confirmed by AFM measurements. (C) 1996 Academic Press, Inc.