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Abstract. Applications of single-walled carbon nanotubes (SWNTs) in medical field imply the use of drug-coupled carbon nanotubes as well as carbon nanotubes functionalized with different chemical groups that change nanotube surface properties and interactions between nanotubes and cells. Covalent attachment of polyethylene glycol (PEG) to carboxylated singlewalled carbon nanotubes (c-SWNT) is known to prevent the nanotubes from interaction with macrophages. Here we characterized nanotube's ability to stimulate coagulation processes in platelet-poor plasma (PPP), and evaluated the effect of SWNTs on platelet aggregation in platelet-rich plasma (PRP). Our study showed that PEG-SWNT did not affect the rate of clotting in PPP, while c-SWNT shortened the clot formation time five times compared to the control PPP. Since c-SWNT failed to accelerate coagulation in plasma lacking coagulation factor XI, it may be suggested that c-SWNT affects the contact activation pathway. In PRP, platelets responded to both SWNT types with irreversible aggregation, as evidenced by changes in the aggregate mean radius. However, the rate of aggregation induced by c-SWNT was two times higher than it was with PEG-SWNT. Cytological analysis also showed that c-SWNT was two times more efficient when compared to PEG-SWNT in aggregating platelets in PRP. Taken together, our results show that functionalization of nanoparticles can diminish their negative influence on blood cells. As seen from our data, modification of c-SWNT with PEG, when only a one percent of carbon atoms is bound to polymer (70 wt %), decreased the nanotube-induced coagulation in PRP and repelled the accelerating effect on the coagulation in PPP. Thus, when functionalized SWNTs are used for administration into bloodstream of laboratory animals, their possible pro-coagulant and pro-aggregating properties must be taken into account.

The dynamics of changes in albumin transport function during hypochlorite-induced oxidation of isolated albumin in blood plasma and serum was studied with a fluorescent probe K-35. Binding of the probe K-35 to albumin was characterized by effective concentration of albumin. Oxidative modification of proteins was evaluated by the content of carbonyl products of protein oxidation and bityrosine fluorescent products. Oxidation with hypochlorite was accompanied by a decrease in the effective concentration of albumin in albumin, diluted plasma, and serum and accumulation of carbonyl products of protein oxidation and bityrosine fluorescent products. The decrease in the effective concentration of albumin during oxidation with hypochlorite can be explained by oxidative damage to albumin binding sites. Oxidative modification of probe K-35 binding sites with hypochlorite contributes to a decrease in effective concentration of albumin under pathological conditions.

Changes in the capacity of fibrinogen subjected to oxidative modification to transform into fibrin under the effect of thrombin and to form a fibrin clot were studied. The effects of oxidized fibrinogen preparations on the clot formation by citrate-treated donor plasma were evaluated by the thrombin time test. Oxidation impaired the capacity of isolated fibrinogen to form a fibrin clot under the effect of thrombin. Addition of oxidized fibrinogen solutions to donor plasma led to prolongation of the plasma clotting time. Maximum addition (33% volume) of oxidized fibrinogen led to a 10-26% prolongation of clotting time in comparison with addition of the same volume of the same solution without fibrinogen.

Oxidative stress plays an important role in cardiovascular diseases and atherosclerosis. Fibrinogen (FB), a central protein of the plasma coagulation cascade, is an independent risk factor of atherosclerosis. Importantly, it can be readily oxidized during oxidative stress and in various pathological conditions. Since endothelial dysfunction plays a key role in atherosclerosis it is interesting to investigate the effect of oxidized fibrinogen (ox FB) on human umbilical vein endothelial cells (HEC). Here, we have investigated the effect of ox FB on the development of programmed death of HEC incubated in vitro for 24 h under two different conditions: (1) at low serum level (0.1%) and in the absence of growth factors ("starvation"); (2) in full medium (5% human fetal serum) with growth factor supplement. Apoptosis was evaluated using analysis of nuclear morphology, phosphatidylserine externalization on the HEC surface and caspase 3 activation. Under starvation conditions characterized by significant cell death and activation of apoptosis addition of unoxi dized FB significantly improved cell survival and prevented caspase 3/7 activation. In the presence of ox FB caspase activity was 1.5 times higher than in the presence of FB, nevertheless, ox FB demonstrated signifi cant protection of HEC. Under optimal cultivation conditions FB caused a 3 fold decrease in the rate of apo ptosis, while ox FB improved cell survival but it was less active than FB. Thus, FB promoted HEC survival under stress conditions (in starvation), however, oxidative modification of this protein decreased its antiapo ptotic activity.