HEPARIN BINDING ON POLY(L-LYSINE) IMMOBILIZED SURFACE

A poly(ethylene-vinyl alcohol) (PEVAL) copolymer surface with immobilized poly(L-lysine) · HBr (PLL · HBr) has been used as a model surface to study the interaction of heparin with polycationic surfaces. The amount of heparin bound from PBS was 0.52 ± 0.19 μg/cm2 on a smooth PLL immobilized PEVAL surface and 1.69 ± 0.26 μg/cm2 on a porous PLL-PEVAL surface. Heparin adsorption kinetic studies indicated that heparin adsorption from plasma or blood exhibited a "two step" profile, which may be related to the effects of competitive binding between heparin and proteins, membrane porosity, and solution viscosity. The time needed to reach heparin binding saturation was 10 min in PBS and 30 min in plasma or blood at flow rate of 100 ml/min. However, under similar experimental conditions, heparin binding in PBS did not reach saturation for 2 h at flow rate of 3 ml/min. The difference in time required to reach saturation for two different flow rates (3 and 100 ml/min) was attributed to the heparin concentration gradient between bulk and surface. Bound heparin was eluted with a basic solution. The recovery of heparin bound from PBS, plasma, and blood was 85 ± 3%, which implied that most of the heparin was tightly bound to protonated amino groups on the side chain of PLL. The data suggest that electrostatic interactions between heparin and PLL may be the driving force for heparin binding. This study offers information for understanding heparin binding onto polycationic surfaces, especially in biological systems. © 1991.