Adsorption/Desorption of Low-density Lipoprotein on a Heparinized Surface of Gold Sensors

Heparin has been considered to be a potentially useful ligand for low-density lipoprotein(LDL) detection and analysis in a clinical context. In order to construct an affinity surface for preferential adsorption of LDL, heparin-modified gold surface(GS-Hep) was fabricated by a self-assembling method and hydrophobic-modified gold surfaces(GS-Hydro) was used as a control. The morphologies of the modified gold surfaces were investigated by atomic force microscopy(AFM) and the quantity of heparin bound to gold surface was assayed by the toluidine blue(TB) colorimetric method. Water contact angles were determined to investigate wettability on GS-Hep and GS-Hydro. Surface plasmon resonance(SPR) technique was used subsequently to detect the selective binding of LDL with heparin. And the investigation on the effect of pH on LDL adsorption suggests that lower pH lead to higher quantities of LDL adsorption on GS-Hep. Compared with GS-Hydro, GS-Hep is selective for LDL from both single and binary protein solutions. Moreover, adsorbed LDL on GS-Hep could be washed off by injecting elution solution, such as NaCl solution, for the purpose of the regeneration of GS-Hep for further LDL adsorption.