W. Okrój

Adhesion, activation, and aggregation of blood platelets and biofilm formation on the surfaces of titanium alloys Ti6Al4V and Ti6Al7Nb†

Titanium alloys are still on the top list of fundamental materials intended for dental, orthopedics, neurological, and cardiovascular implantations. Recently, a special attention has been paid to vanadium-free titanium alloy, Ti6Al7Nb, that seems to represent higher biocompatibility than traditional Ti6Al4V alloy. Surprisingly, these data are not thoroughly elaborated in the literature; particularly there is a lack of comparative experiments conducted simultaneously and at the same conditions. Our study fills these shortcomings in the field of blood contact and microbiological colonization. To observe platelets adhesion and biofilm formation on the surfaces of compared titanium alloys, fluorescence microscope Olympus GX71 and scanning electron microscope HITACHI S-3000N were used. Additionally, flow cytometry analysis of platelets aggregation and activation in the whole blood after contact with sample surface, as an essential tool for biomaterial thrombocompatibility assessment, was proposed. As a result of our study it was demonstrated that polished surfaces of Ti6Al7Nb and Ti6Al4V alloys after contact with whole citrated blood and E. coli bacterial cells exhibit a considerable difference. Overall, it was established that Ti6Al4V has distinct tendency to higher thrombogenicity, more excessive bacterial biofilm formation and notable cytotoxic properties in comparison to Ti6Al7Nb. However, we suggest these studies should be extended for other types of cells and biological objects.

The blood platelet proteome is changed in UREMIC patients

Comparative analysis of the protein profile of blood platelets isolated from nondialyzed and hemodialyzed uremic patients and healthy controls has been performed. These preliminary results indicate markedly changed expression of several proteins in blood platelets from both groups of patients compared with controls, with dramatic changes in hemodialyzed patients in the over-expression of low molecular peptides with a very wide range of pI values.

Thrombocompatibility of sol-gel titanium dioxide coatings deposited on stainless steel substrate

Abstract Titanium dioxide (TiO2) can be used as protective and biocompatible coatings. Properties of these coatings strongly depend on a method and conditions of the deposition process. The aim of this study was to investigate the contact of whole blood with sol-gel TiO2 films deposited on stainless steel (316L) substrates by the dip–coating method and treated at different temperatures. The TiO2 films were annealed at temperatures in the range of 300–800°C. Different structures of TiO2 (amorphous, anatase and rutile) were obtained. Samples were characterised in regard to morphology, thickness, roughness, wettability and phase composition. An in vitro cell adhesion and cytofluorymetry tests were also performed to characterise the quantity and morphology of adhered blood platelets and platelet activation and aggregation in the blood samples after contact with the studied surfaces. The TiO2 sol-gel coating annealed at 800°C (rutile) showed better thrombocompatibility in comparison with other studied coatings.

Preliminary testing of silicone-urethane elastomers as substrates in human cell culture

Abstract Silicone-urethanes, polymers combining the characteristics of two widely used biomaterials, i.e. polyurethanes and silicones, are highly valued in many applications, including medical implants. To assess properties of these materials in contact with living cells, a set of different silicone-urethane materials, candidates for tissue engineering scaffolds, was synthesized and characterized. Two different oligomeric siloxane diols: Tegomer-2111 (Teg) and KF-6001 (KF), and two different types of diisocyanate, MDI and IPDI, were used in synthesis. Blood platelets adhesion to surfaces of selected materials showed a higher thrombogenicity of material based on Teg. Human fibroblasts were used in in vitro biocompatibility tests. The viability of cells cultured on silicone-urethanes was tested by XTT assay. Teg-based silicone-urethanes showed a significantly higher biocompatibility than those based on KF. Materials based on MDI compared to IPDI were found to be significantly more favoured by cells, not necessarily due to the type of diisocyanate but maybe also because of the necessity of using potentially toxic catalyst which accompanies the use of IPDI. Our studies indicate that silicone-urethanes are potent materials for tissue engineering products development. On the basis of the observations performed in cell culture, Tegomer- 2111 as oligomeric siloxane diol and MDI as diisocyanate are recommended as starting materials for silicone-urethane scaffolds synthesis.

Interaction of body fluids with carbon surfaces

The use of medical implants allows one to improve patients lives, and quite often it can return patients back to normal activity in their personal and professional lives. One of the most difficult problems, which is necessary to solve, is a proper selection of the materials to be used for implant construction and/or implant coating. The surface of an implant is exposed to continuous contact with body fluids and several unwanted processes may occur there. Titanium and its alloys are generally accepted as the best tolerated materials for implants. But currently many efforts are focused on thin layers of crystalline carbon, i.e. diamond like carbon (DLC) and nanocrystalline diamond (NCD), used for coating of metal implants. This technology was successfully applied in bone surgery (screws), and more recently in heart surgery (stents). We found, with the fluorescence microscopy technique, that bacterial growth was possible on stainless steel, to a lesser degree on titanium, but NCD was almost totally resistant to bacterial colonization.

SPR Biosensor Technique Supports Development in Biomaterials Engineering

Various biomaterials are presently employed in the production of a very wide spectrum of medical implants. The choice of biomaterial is of course determined by the medical application for which it is intended and to date no one biomaterial has been found to be fully biocompatible and biotolerant. Furthermore, it is a well known fact that quite often implants must be removed due to tissue reactions and resultant health problems (Khan et al. 2008; Schierholz& Beuth, 2001). The key role in implant tolerance depends on a very short period of time during which the biomaterial surface first comes into contact with body fluids. During this time, water molecules come into contact with the surface of the biomaterial and the results of this reaction determine the further course of events. Water molecule interaction is generally dependent on surface nanostructure and highly dependent on its energy and hydrophobicity. The next stage of interaction, which depends on the presence of water on the biomaterial surface, is the creation of a thin protein film on this surface. A hydrophilic surface will collect a large amount of hydrophilic proteins readily available in body fluids, however these proteins are weakly adsorbed and can be easily removed or replaced by other molecules. A hydrophobic surface will adsorb proteins by their hydrophobic regions often causing changes in protein structure and biological activity. The final stage, cellular attachment, adhesion and proliferation depends on the profile of the adsorbed proteins, their accessibility and a proper spatial structure which enables expression of biologically active sites. Thus, the type of protein present on a biomaterial surface seems to be crucial for biomaterial tolerance in the human body. The most common experimental models developed to characterize protein adsorption on biomaterial surfaces involve the incubation of proteins in contact with a studied surface and the estimation of adsorbed proteins by a variety of methods including electrophoretic, enzymatic or immunoenzymatic approaches together with a number of labeling techniques. The common disadvantages of these techniques is that it is not possible to observe protein adsorption as a kinetic process and protein quantification is strongly limited by the sensitivity of the methods used, which is usually limited to nanograms per square millimeter. Surface