The interaction of polymer surfaces with blood

Some general aspects of the interaction of foreign materials with blood are summarized. The role of protein adsorption in this interaction is briefly discussed. In an attempt to produce more stable antithrombogenic surface coatings than the well-known heparin-bonded surfaces, a method is described in which a high-molecular-weight polyelectrolyte is bound to polymer surfaces. In vitro experiments carried out with freshly drawn human blood show a reduced platelet adhesion on such surfaces

Proteins involved in the Vroman effect during exposure of human blood plasma to glass and polyethylene

The amounts of fibrinogen adsorbed to glass from various human blood plasmas have been measured as a function of time. The plasmas were 11 single donor plasmas, pooled plasma, a single donor high molecular weight kininogen (HMWK)-deficient plasma and HMWK-deficient plasma, which had been reconstituted with HMWK. For adsorption times between 1 min and 1 h more fibrinogen adsorbed from HMWK-deficient plasma compared with the amounts of fibrinogen which adsorbed from the other plasmas. This result supports the conclusion of several authors that HMWK is involved in the displacement of fibrinogen, initially adsorbed from normal human plasma to glass. Glass surfaces, pre-exposed to solutions of plasma and subsequently exposed to 1:1 diluted plasma, gives rise to a relatively high adsorption of HMWK which is independent of the plasma concentration of the precoating solution. The results indicate that HMWK from 1:1 diluted plasma is involved in the displacement of proteins from glass surfaces which had been pre-exposed to solutions with a low plasma concentration. Experiments with polyethylene as a substrate reveal that high density lipoprotein (HDL) from 1:1 diluted plasma is involved in the displacement of proteins from polyethylene surfaces which had been pre-exposed to solutions with a low plasma concentration. Moreover, evidence is presented that substantial amounts of albumin and fibrinogen, adsorbed from 1:1000 diluted plasma to glass and polyethylene, are displaced from the surfaces of these materials by proteins from 1:1 diluted plasma different from HMWK and HDL

Detection of surface-adsorbed (lipo)proteins by means of a two-step enzyme-immunoassay: a study on the Vroman effect

In view of reports on the involvement of high-molecular-weight (HMW) kininogen and high-density lipoprotein (HDL) in the Vroman effect, we studied the adsorption of fibrinogen, HMW kininogen, HDL and several other proteins from pooled human plasma and congenitally HMW kininogen-deficient plasma onto glass and low-density polyethylene, both as a function of the plasma concentration and the contact time. Mixtures of purified (lipo)proteins were also included in the study. Protein adsorption was determined by means of a two-step enzyme-immunoassay. Our results support the hypothesis that HMW kininogen is involved in the displacement of fibrinogen, which is almost instantly adsorbed from normal plasma onto glass. On hydrophobic polymers like polyethylene, the low amounts of adsorbed fibrinogen and HMW kininogen from plasma and concentrated plasma solutions may be due to a preferential adsorption of HDL

Thin-layer chromatography of pigments from reaction center particles of Rhodopseudomonas spheroides

1. Pigments extracted from reaction center particles of Rhodopseudomonas spheroides were separated and identified by means of thin-layer chromatography.\ud \ud 2. The results strongly suggest that bacteriochlorophyll a is the only bacteriochlorophyll pigment present in reaction centers.\ud \ud 3. Other compounds identified are bacteriopheophytin a, ubiquinone-10 and spheroidene

Antithrombin activity of a polyelectrolyte synthesized from cis-1,4-polyisoprene

A polyelectrolyte synthesized from cis-1,4-polyisoprene, containing aminosulfonate and carboxylate groups was shown to have an anticoagulant activity of about 1/30 compared with heparin. Because the substance prevents the coagulation of plasma in the presence of thrombin it is assumed that it acts as an antithrombin

Synthetic polymers with anticoagulant activity

Polymers with C=C bonds have been modified by reaction with chlorosulfonyl isocyanate (CSI). Addition products were obtained in yields varying from 60% to 75%. Reaction of these products with NaOH yielded polyelectrolytes with sulfamate and carboxylate groups, whereas from the reaction with NH4OH polyelectrolytes with sulfamate and carbonamide groups, were obtained. The polyelectrolytes showed anticoagulant activity depending on the structure and on the presence of both sulfamate and carboxylate groups. These groups are essential for the anticoagulant activity, because N-S bond cleavage in the sulfamate groups as well as substitution of carboxylate by carbonamide groups resulted in loss of activity. From the recalcification times of bovine plasma, it could be concluded that the most active polyelectrolyte had an activity of 6-7% compared with heparin. However, determination of the activated clotting time of blood from rabbits showed that this compound had an in vivo activity of 50% in comparison with heparin

Preferential adsorption of high density lipoprotein (HDL) in blood plasma/polymer interaction

A few studies on the adsorption of plasma proteins to polymeric surfaces show that major plasma proteins: albumin (Alb), fibrinogen (Fb) and immunoglobulin (IgG) are adsorbed in much smaller quantities from plasma than from protein solutions (1,2). Present results show that this difference in adsorption is due to the preferential adsorption of high density lipoprotein from plasma onto the material surfaces studied (PVC and PS)

Adhesion of endothelial cells and adsorption of serum proteins on gas plasma-treated polytetrafluoroethylene

From in vitro experiments it is known that human endothelial cells show poor adhesion to hydrophobic polymers. The hydrophobicity of vascular prostheses manufactured from Teflon® or Dacron® may be the reason why endothelialization of these grafts does not occur after implantation in humans. We modified films of polytetrafluoroethylene (Teflon®) by nitrogen plasma and oxygen plasma treatments to make the surfaces more hydrophilic. Depending on the plasma exposure time, modified polytetrafluoroethylene surfaces showed water-contact angles of 15–58°, versus 96° for unmodified polytetrafluoroethylene. ESCA measurements revealed incorporation of both nitrogen- and oxygen-containing groups into the polytetrafluoroethylene surfaces, dependent on the plasma composition and exposure time. The thickness of the modified surface layer was ~1 nm. The adhesion of cultured human endothelial cells from 20% human serum-containing culture medium to modified polytetrafluoroethylene surfaces with contact angles of 20–45° led to the formation of a monolayer of cells, which was similar to the one formed on tissue culture polystyrene, the reference surface. This was not the case when endothelial cells were seeded upon unmodified polytetrafluoroethylene. Surface-modified expanded polytetrafluoroethylene prosthesis material (GORE TEX® soft tissue) also showed adhesion of endothelial cells comparable to cell adhesion to the reference surface. The amounts of serum proteins, including fibronectin, adsorbed from serumcontaining medium to modified polytetrafluoroethylene surfaces were larger than those adsorbed to unmodified polytetrafluoroethylene. Moreover, the modified surfaces probably allow the exchange of adsorbed serum proteins with cellular fibronectin

Interaction of cultured human endothelial cells with polymeric surfaces of different wettabilities

The in vitro interaction of human endothelial cells (HEC) and polymers with different wettabilities in culture medium containing serum was investigated. Optimal adhesion of HEC generally occurred onto moderately wettable polymers. Within a series of cellulose type of polymers the cell adhesion increased with increasing contact angle of the polymer surfaces. Proliferation of HEC occurred when adhesion was followed by progressive flattening of the cells.\ud \ud Our results suggest that moderately wettable polymers exhibit a serum and/or cellular protein adsorption pattern that is favourable for growth of HEC

Deposition of endothelial fibronectin on polymeric surfaces

Cellular fibronectin is deposited on tissue culture polystyrene during the adhesion and spreading of cultured human endothelial cells (HEC). Following the seeding of HEC upon this polymer, larger amounts of fibronectin are deposited as both cell density and incubation time increase. Our results indicate that the ability to deposit cellular fibronectin onto a polymeric surface is a condition for the spreading and proliferation of HEC