Evaluation of platelet adhesion and activation on polymers: Round-robin study to assess inter-center variability.

The regulatory agencies provide recommendations rather than protocols or standard operation procedures for the hemocompatibility evaluation of novel materials e.g. for cardiovascular applications. Thus, there is a lack of specifications with regard to test setups and procedures. As a consequence, laboratories worldwide perform in vitro assays under substantially different test conditions, so that inter-laboratory and inter-study comparisons are impossible. Here, we report about a prospective, randomized and double-blind multicenter trial which demonstrates that standardization of in vitro test protocols allows a reproducible assessment of platelet adhesion and activation from fresh human platelet rich plasma as possible indicators of the thrombogenicity of cardiovascular implants. Standardization of the reported static in vitro setup resulted in a laboratory independent scoring of the following materials: poly(dimethyl siloxane) (PDMS), poly(ethylene terephthalate) (PET) and poly(tetrafluoro ethylene) (PTFE). The results of this in vitro study provide evidence that inter-laboratory and inter-study comparisons can be achieved for the evaluation of the adhesion and activation of platelets on blood-contacting biomaterials by stringent standardization of test protocols.

The effect of the major components of Salvia Miltiorrhiza Bunge on bone marrow cells.

Salvia Miltiorrhiza Bunge (SMB), a traditional Chinese medicinal herb, has been alleged to support bone healing. However, the effects of the isolated major components of SMB on osseous cells and their corresponding effective doses are still unclear. In the present study, the effects of three components of SMB, including tanshinone IIA (Ts), salvianolic acid B (salB) and protocatechuic aldehyde (Pca), on mesenchymal bone marrow cells with the potential for osteoblastic differentiation were investigated. Various concentrations of Ts, salB and Pca were added to a rat bone marrow cell culture. The total metabolic activity and differentiation of bone marrow cells were evaluated by a metabolic assay and alkaline phosphatase (ALP) activity, respectively. The morphology and number of cells was observed by phase contrast microscopy and fluorescent microscopy after propidium iodide staining, respectively. Ts suppressed the growth and differentiation of bone precursor cells. SalB exhibited a biphasic effect: the high concentration of 160 microg/mL significantly depressed the population of bone marrow cells, however, lower concentrations (3-80 microg/mL) enhanced the total metabolic activity and their ALP expression. Pca suppressed the bone marrow cell population in a dose-dependent manner. Therefore, SalB has the potential to ameliorate bone healing by stimulating both the total metabolic activity and ALP activity of osteoblastic cells. Aqueous extracts, which preferably contain salB over Pca and are free of Ts therefore are recommended for bone formation.

Hemocompatibility of low-friction boron-carbon-nitrogen containing coatings.

Mechanical heart valves are exposed to extreme mechanical demands, which require a surface showing not only nonhaemostatic properties, but also wear resistance and low friction. As alternative to different forms of amorphous carbon (a-C), so-called diamond-like carbon (DLC), the suitability of boron carbonitride (BCN) coatings is tested here for hemocompatible coatings. They have similar mechanical properties like a-C surfaces, but superior chemical stability at ferrous substrates or counterparts. BCN films with different nitrogen content were compared with hydrogenated a-C films regarding their mechanical properties, surface energy, adsorption of albumin and fibrinogen, blood platelet adherence, and activation of the contact system of the clotting cascade and kinin system. Similar mechanical properties and biological response have been found in the BCN films with respect to a-C, indicating the potential of these coatings for biomedical applications. The increase in the crystallinity and tribological properties of the BCN samples with a higher incorporation of N was also followed by a lower protein adsorption and low activation of the contact system, but an increased adherence of thrombocytes.

Bioactivity of titanium following sodium plasma immersion ion implantation and deposition.

Bio-activation of titanium surface by Na plasma immersion ion implantation and deposition (PIII and D) is illustrated by precipitation of calcium phosphate and cell culture. The bioactivity of the plasma-implanted titanium is compared to that of the untreated, Na beam-line implanted and NaOH-treated titanium samples. Our data show that the samples can be classified into two groups: non-bioactive (untreated titanium and beam-line Na implanted titanium) and bioactive (Na-PIII and D and NaOH-treated titanium). None of the four types of surfaces exhibited major cell toxicity as determined by lactate dehydrogenase (LDH) release. However, the LDH release was higher on the more bioactive PIII and NaOH-treated surfaces. From a morphological point of view, cell adherence on the NaOH-treated titanium is the best. On the other hand, the cell activity and protein production were higher on the non-bioactive surfaces. The high alkaline phosphatase activity per cell suggests that the active surfaces support an osteogenic differentiation of the bone marrow cells at the expense of lower proliferation. The use of Na-PIII and D provides an environmentally cleaner technology to improve the bioactivity of Ti compared to conventional wet chemical processes. The technique is also particularly useful for the uniform and conforming treatment of medical implants that typically possess an irregular shape and are difficult to treat by conventional ion beam techniques.

Hydroxyapatite growth induced by native extracellular matrix deposition on solid surfaces.

Biological systems have a remarkable capability to produce perfect fine structures such as seashells, pearls, bones, teeth and corals. These structures are composites of interacting inorganic (calcium phosphate or carbonate minerals) and organic counterparts. It is difficult to say with certainty which part has the primary role. For example, the growth of molluscan shell crystals is thought to be initiated from a solution by the extracellular organic matrix (ECM). According to this theory, the matrix induces nucleation of calcium containing crystals. Recently, an alternative theory has been put forward, stating that a class of granulocytic hemocytes would be directly involved in shell crystal production in oysters. In the work presented here the surface of AISI 316 stainless steel was modified by deposition of ECM proteins. The ability of the modified substrates to induce nucleation and growth of hydroxyapatite (HA) from simulated body fluid (SBF) was examined by a kinetic study using two methods: (1) a simple soaking process in SBF and (2) a laser-liquid-solid interaction (LLSI) process which allows interaction between a scanning laser beam and a solid substrate immersed in SBF. The deposited HA layers were investigated by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). It was found that a coating of stainless steel surface with native ECM proteins induced nucleation and growth of HA and facilitated its crystallization. By the process of simple soaking of the samples, irrespective of their horizontal or vertical position in the solution, HA layers were grown due to the reactive ECM-coated stainless steel surface. It was shown that the process occurring in the first stages of the growth was not only a result of the force of gravity. The application of the LLSI process strongly influenced HA formation on the ECM-modified substrates by promoting and enhancing the HA nucleation and growth through a synergistic effect of a few stimuli, i.e., the modified solid surface, the laser beam and the aqueous solution.

Drug release from polyureaurethane coating modified by plasma immersion ion implantation.

A crosslinked polyurethanurea (PUU) coating was synthesised from a solution on metal vascular stents. In the model system the glucocorticoid prednisolone was inserted into the film by the equilibrium swelling method; after this plasma immersion ion implantation (PIII) was applied to modify the coating for improved release kinetics. This treatment causes the formation of oxygen-containing and unsaturated carbon-carbon groups in the PUU and a destruction of the drug in the surface layer. As a consequence, the release rate of prednisolone to water becomes more stable with time than it is at the untreated coating. In this drug release system PIII treatment prevents an initial toxically high release of the drug. By this it allows the incorporation of a higher amount of the drug and an extended action.

Ion beam treatment of titanium surfaces for enhancing deposition of hydroxyapatite from solution.

Surface coating with hydroxyapatite (HA) is a common way to improve the osseointegration of orthopaedic and dental titanium (Ti)-based materials. The main problems with current techniques are changes in composition during heating and poor adhesion to the surface. An alternative method is deposition of HA onto an activated surface out of a solution. The present work studies the surface treatment involving ion implantation of Na into Ti to induce a modification in chemistry and morphology, showing sodium titanate (Na(2)TiO(3)) incorporated within the surface layer with concentration, depth distribution, and morphology depending on the parameters of the ion implantation. Such ion-implanted Ti surfaces actively induce heterogeneous precipitation of HA from a simulated body fluid containing physiological concentrations of calcium and phosphate ions. This is compared with the activation by NaOH etching. The growth of bone forming cells on the pure Na implanted surface is oriented without an increased bone formation. Cell growth on the NaOH etched surface is reduced. After deposition of HA on both surfaces cell the growth pattern was improved.

[Influence of bioactive glasses on the respiratory burst metabolism of polymorphonuclear neutrophils]. / Einfluss von bioaktiven Gläsern auf den Respiratory Burst Metabolismus von Granulozyten.

BACKGROUND: Bio-glasses are bioactive materials used to coat implants. The immunological reaction to wear particles from such coatings has hardly been investigated. The generation of reactive oxygen species by polymorphonuclear neutrophils (PMN) on phagocytosis of particles might elicit further immune reactions. METHODS: The production of reactive oxygen species was investigated in whole blood in the form of chemiluminescence using the probes luminol and lucigenin. RESULTS: Bioglass particles stimulated PMN to generate free radicals as a function of the bioactivity of the composition. This activation was significantly reduced by prior soaking of the particles. Extracts of the bioactive glasses also inhibited the liberation of free radicals upon the stimulus opsonized zymosan. CONCLUSION: Our results show that despite the proven good biocompatibility of bioactive glasses, further in vivo checks in the early stages of the reaction are needed.