Different kinetics of the respiratory burst response in granulocytes, induced by serum from blood coagulated in contact with polymer materials

Blood-Contacting Biomaterials: In Vitro Evaluation of the Hemocompatibility

Hemocompatibility of blood-contacting biomaterials is one of the most important criteria for their successful in vivo applicability. Thus, extensive in vitro analyses according to ISO 10993-4 are required prior to clinical applications. In this review, we summarize essential aspects regarding the evaluation of the hemocompatibility of biomaterials and the required in vitro analyses for determining the blood compatibility. Static, agitated, or shear flow models are used to perform hemocompatibility studies. Before and after the incubation of the test material with fresh human blood, hemolysis, cell counts, and the activation of platelets, leukocytes, coagulation and complement system are analyzed. Furthermore, the surface of biomaterials are evaluated concerning attachment of blood cells, adsorption of proteins, and generation of thrombus and fibrin networks.

Just scratching the surface

BACKGROUND AND OBJECTIVE

Different types of polymer surfaces affect the activation of platelets and coagulation pathway containers depending on their surface qualities. Importantly, this could produce variability of coagulation results obtained with thrombelastographical analysis. We assessed the effects of blood storage on thrombelastograph, TEG, variables using polypropylene and polycarbonate containers.

METHODS

An in vitro experiment was performed, with eight volunteers in each limb. Fresh whole blood was stored in polypropylene or polycarbonate tubes prior to TEGanalysis, to assess the role of these plastics in the TEG results obtained.

RESULTS

The polycarbonate tubes displayed slower onset of coagulation and greater variability of data for all four basic TEG variables (r-time, k-time, alpha-angle and maximum amplitude, P < 0.05). Polycarbonate results fell outside manufacturer reference ranges.

CONCLUSIONS

It is likely that this is due to the altered surface properties and charge effects of the containers affecting proteins and platelets differently. Caution should be used in choosing which containers are used for storage of fresh blood prior to coagulation assessment, as variable results will follow where different types of plastic containers are employed.

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.

Respiratory burst response of peritoneal leukocytes adhering to titanium and stainless steel

Titanium sheets, made hydrophilic by oxidative cleaning or hydrophobic by treatment with butanol, and stainless steel sheets with different patterns of pores (straight phi = 0.8 mm) were implanted into the peritoneal cavity of mice. The implants were removed after 2 h, and the surface-adhering leukocytes were stained with propidium iodide and fluorescein diacetate to quantitate cell adhesion and to indicate the presence of leaks in the cell membrane. The ability of the surface-adhering leukocytes to mount a respiratory burst response after stimulation with PMA or zymosan was measured by chemiluminiscence. The results show that stainless steel without pores induces membrane leakage in 80% of the surface-adhering leukocytes compared with 65% of cells adhering to porous steel. Hydrophilic titanium induces membrane leakage in 48% of the surface-adhering leukocytes compared with 19% of cells adhering to hydrophobic titanium. The respiratory burst response of the surface-adhering leukocytes stimulated with PMA was attenuated on stainless steel and hydrophilic titanium compared with hydrophobic titanium. Thus, butanol treatment of titanium and pores in stainless steel increase the biocompatibility of the materials.