Interactions between whole blood and foreign materials: surface-adsorbed cellulose ethers reduce granulocyte activation by inflammatory mediators

Effect of conjugated linoleic acid immobilization on the hemocompatibility of cellulose acetate membrane

Conjugated linoleic acid (CLA) was covalently immobilized onto cellulose acetate (CA) membranes. The effects of CLA immobilization on the blood coagulation, platelet aggregation, and oxidative stress were evaluated using human blood. The resulting CLA grafting CA membranes were characterized with X-ray photoelectronic spectroscopy (XPS). The complete blood count (CBC) and coagulation time (CT) was evaluated in vitro for the hemocompatibility. Human serum albumin (HSA) and human plasma fibrinogen (HPF) was evaluated for the protein affinity. The production of reactive oxygen species (ROS) was measured by chemiluminescence (CL) method to evaluate the oxidative stress. The results showed that the CLA-immobilizing CA membrane could keep the CBC values more stable than unmodified CA membrane. The CLA-immobilized CA membranes also showed longer CT and less adsorption of plasma proteins. CLA-immobilized CA membrane could keep the CL counts of hydrogen peroxide and superoxide values more stable than unmodified CA membrane. These results suggest that a CLA-immobilized CA membrane could offer protection for patients against oxidative stress and would be helpful for reducing the dosage of anticoagulant during hemodialysis.

UHMWPE oxidation increases granulocytes activation: a role in tissue response after prosthesis implant

Ultra-high molecular weight polyethylene (UHMWPE), a biopolymer widely used in orthopaedic implants, is oxidized during gamma-ray sterilization; such surface oxidation is considered as major responsible for inflammation and prosthesis failure. As granulocytes are involved in first contact inflammation, we have measured their oxidative burst by flow cytometry using dihydrorhodamine 123 (DRH) to evaluate their activation following contact with normal and oxidized UHMWPE. Peripheral blood cells (obtained by lysed blood) were loaded with DRH, seeded onto polystyrene, normal and heat-oxidized UHMWPE disks for 30min and then collected for analysis. Granulocytes were individuated using FSC and SSC signals and their cell associated green fluorescence was analyzed. Both normal and oxidized UHMWPE stimulated granulocytes activation as showed by the mean fluorescence emitted (109.3+/-3.8 and 150.1+/-9.2, respectively) compared to control samples (81.6+/-0.3). Moreover oxidized UHMWPE activated a significantly higher percentage of granulocytes (73.35+/-5.2%) compared to not-oxidized UHMWPE (21.5+/-3.8%). UHMWPE surface oxidation responsible for increased granulocyte activation seems to play a role in tissue response to implants.

Structural alteration of erythrocyte cell membrane in presence of artificial prostheses: a radiowave dielectric spectroscopy study

The exposure of a biomaterial to blood gives rise to complex reactions playing an important role in many biological phenomena, such as the problem of biocompatibility and the mechanism of cardiovascular and thromboembolic diseases. In the present work, we use a frequency-domain dielectric spectroscopy approach to evaluate possible changes in the passive electrical parameters of the erythrocyte membrane, i.e., the membrane conductivity sigma(s) and the membrane permittivity epsilon(s), after the insertion of a prosthesis (mean implantation time 8 days) in the circulatory system of patients treated for aortic aneurysm and the consequent interactions of erythrocyte cells with the biomaterial surface. We observe an increase of both the membrane conductivity and membrane permittivity, indicating changes at molecular level in the structural organization of the membrane. These membrane alterations can be viewed as precursory events for the initiation of the complex sequence of enzymatic reactions that take place on the material surface. Our results, although preliminary imply that a direct interaction between erythrocyte cell membrane and vascular prostheses may occur, causing a marked alteration in the electrical properties of the cell membrane. These findings might have relevant clinical implications and might offer possibilities to predict biocompatibility of biomaterials and give some further suggestions to resolve the problem of biomaterial-associated thrombogenicity.