Plasmatic antiproteinase activity enhancement by insoluble functionalized polystyrene surfaces

Anticoagulant and antiprotease activities of a heparinoid sulfated glucoside-bearing polymer

We studied anticoagulant and antiprotease activities of the poly(glucosyloxyethyl methacrylate) sulfate [poly(GEMA)-sulfate] in plasma and purified enzyme systems in order to evaluate the anticoagulant behavior of a heparin-like sulfated glucoside-bearing polymer. As a result, we found that poly(GEMA)-sulfate can inhibit some coagulation proteases, although its antiprotease behavior differed from those of heparin and dextran sulfate. Poly(GEMA)-sulfate could not enhance antithrombin activity; therefore, we did not observe any significant inhibition of Factor Xa via antithrombin. However, we found that poly(GEMA)-sulfate was able to inhibit thrombin through the activation of heparin cofactor II. In addition, poly(GEMA)-sulfate was able to inhibit Tenase. In our previous research. we found that the anticoagulant activity of poly(GEMA)-sulfate is due primarily to the formation of an insoluble complex with fibrinogen. This paper showed that the antiprotease activities of poly(GEMA)-sulfate contribute to some extent to its anticoagulant activity.

Heparin-like functionalized polymer surfaces: discrimination between catalytic and adsorption processes during the course of thrombin inhibition

Thrombus formation on blood-contacting artificial surfaces is a major problem. Antithrombogenic polymer surfaces have been obtained either by heparin binding, or by grafting sulphonate and/or amino acid sulphonamide groups on insoluble polystyrene. In addition to their capacity to adsorb thrombin, such surfaces were shown to be able to catalyse its inhibition by antithrombin III (AT), i.e. they are endowed with heparin-like activity. The results were mainly obtained by using clotting assays. In many cases, delineating adsorption and catalytic processes by such assays is not possible when evaluating anticoagulant polymer surfaces. To overcome this problem, the kinetics of thrombin adsorption and inhibitions by AT and heparin cofactor II (HC) in the presence of such surfaces have been measured by using an assay performed with a thrombin-specific chromogenic substrate. A simple kinetic model of thrombin consumption is proposed. The relevant calculations, carried out with the help of a computer program, lead to determination of relative second order rate constants of thrombin adsorption and inhibitions by AT and HC in the presence of the polymers. In addition to thrombin adsorption, polystyrene surfaces bearing only sulphonate groups catalyse inhibition by AT, whereas polystyrene surfaces bearing either aspartate, glycinate or isophthalate sulphonamide groups catalyse both inhibitions by AT and HC.