PLASMINOGEN ADSORPTION TO SULFONATED AND LYSINE DERIVATIZED MODEL SILICA GLASS MATERIALS

Silica glass and silylated silica glass have been used extensively as model surfaces for studying the interactions of biological systems wit h specific chemical functions. In this work, the adsorption of plasmin ogen to silylated silica glass materials has been investigated with th e objective of providing data for the development of a profibrinolytic or clot lysing surface for blood-contacting applications. The adsorpt ion of plasminogen from Tris buffer to silica glass, lysine modified s ilica glass, and its sulfonated silica glass precursor has been invest igated. The isotherms (25-degrees-C) suggest high affinity, Langmuir t ype adsorption. Adsorption capacities are in the order sulfonated sili ca > lysinized silica > unmodified silica. Estimates of the apparent a ffinity constants based on the Langmuir equation indicate that the aff inity of plasminogen is greater for the lysinized surface than for eit her the silica glass or sulfonated silica glass. Experiments on the ad sorption of plasminogen to the sulfonated and lysinized silica glass i n the presence of epsilon-amino caproic acid (EACA), known to interfer e with plasminogen binding to lysine, were also carried out. Adsorptio n plateau values for the sulfonated surface with and without EACA in t he buffer were the same. For the lysinized surface, adsorption was red uced in the presence of EACA. Desorption experiments against Tris buff er showed that for the lysinized and sulfonated surfaces, 70-80% of th e protein was irreversibly bound, with slightly higher reversibility o n the lysinized surface. It is concluded that the mechanisms of adsorp tion of plasminogen to the lysinized surface and sulfonated surface ar e different, and that the lysine binding sites of plasminogen may be u tilized in its interactions with the lysinized surface. (C) 1994 Acade mic Press, Inc.