Interactions of plasminogen and fibrinogen with model silica glass surfaces: Adsorption from plasma and enzymatic activity studies

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Abstract
The adsorption of fibrinogen and plasminogen from plasma to silica glass, sulfonated silica glass, and lysinederivatized silica glass has been investigated. The data indicate that the sulfonated material has a high affinity for both fibrinogen and plasminogen, but that the ratio of plasminogen to fibrinogen is greater on the lysinederivatized surface. The adsorption data also suggest plasminogen as a possible contributor to the fibrinogen Vroman effect, whereby initially adsorbed fibrinogen is displaced from the surface. The plasmin activity of plasminogen adsorbed to the lysine‐derivatized silica glass and its sulfonated precursor was assessed by both a chromogenic substrate assay and a radioimmunoassay for the plasmin cleavage product of fibrinogen, the Bβ 1–42 peptide. The data indicate that (1) the adsorbed plasminogen is not inherently plasmin‐like; (2) the enzymatic activity associated with the bound plasminogen is significantly enhanced on both surfaces in the presence of activator; and (3) in the presence of activator, the plasmin activity per mole of bound plasminogen on the lysinized material is approximately a factor of two greater than on the sulfonated material based on the chromogenic substrate assay, and a factor of four greater based on the Bβ 1–42 radioimmunoassay. The lysinized material thus exhibits several properties that are different from its sulfonated precursor. It adsorbs more plasminogen relative to fibrinogen after the Vroman peak, and this adsorbed plasminogen appears to be in a conformation that is more readily activated to plasmin. Once activated, the surface bound plasmin shows enhanced ability to cleave either a low molecular weight chromogenic substrate or a macromolecular substrate. These properties appear to be directly related to lysine residues on the surface and may be the result of specific conformational changes occurring when plasminogen engages its lysine binding sites. © 1994 John Wiley & Sons, Inc.