Isabelle Dion

TiN coating : surface characterization and haemocompatibility

The left ventricular assist device under consideration is based on the principle of the Maillard-Wankel rotary pump. The construction materials must meet stringent requirements. Titanium nitride was chosen for its surface properties and graphite for its bulk characteristics. The purpose of this study was to characterize the chemical vapour deposition titanium nitride coating via morphology, roughness, crystallinity, chemical composition, to report and discuss the results of in vitro haemocompatibility tests (protein adsorption, platelet retention, haemolysis) and to discuss physico-chemical and biological results. This chemical vapour deposition titanium nitride coating is well tolerated by the blood despite its surface irregularities, and appears as a good candidate material after improvements.

Physico-chemistry and cytotoxicity of ceramics: Part II Cytotoxicity of ceramics

General cytotoxicity was assayed for ceramic (Al2O3, ZrO2/Y2O3, AIN, B4C, BN, SiC, Si3N4, TiB4, TiC, TiN) diamond and graphite powders, using 3T3 Balb/c permanent cell lines. Neutral red test was carried out in order to establish cell viability. Further investigations were undertaken on human differentiated cells (human umbilical venous endothelial cells): cell behaviour (MTT assay, total cell protein content) and differentiation (immunofluorescence) were studied. In both cases, no cytotoxic effect has been noticed. All the impurities contained at low concentration in these powders do not seem to present any effect. The correlation which has been previously observed between cytotoxicity-cell culture response and blood haemolysis for polymers has not been established here for ceramic powders. We conclude that all the ceramic powders tested here and therefore the corresponding bulk ceramics or ceramic coatings do not induce any cytotoxic effect.

Hemocompatibility of titanium nitride.

The left ventricular assist device is based on the principle of the Maillard-Wenkel rotative pump. The materials which make up the pump must present particular mechanical, tribological, thermal and chemical properties. Titanium nitride (TiN) because of its surface properties and graphite because of its bulk characteristics have been chosen. The present study evaluated the in vitro hemocompatibility of TiN coating deposited by the chemical vapor deposition process. Protein adsorption, platelet retention and hemolysis tests have been carried out. In spite of some disparities, the TiN behavior towards albumin and fibrinogen is interesting, compared with the one of a reference medical grade elastomer. The platelet retention test gives similar results as those achieved with the same elastomer. The hemolysis percentage is near to zero. TiN shows interesting characteristics, as far as mechanical and tribological problems are concerned, and presents very encouraging blood tolerability properties.

Blood haemolysis by ceramics

Ceramics are more and more frequently under consideration for construction of blood-contacting devices, i.e. cardiac valves or cardiac assist devices. This study evaluated the haemolysis eventually initiated in vitro by ceramic powders (Al2O3, ZrO2/Y2O3, AlN, B4C, BN, SiC, Si3 N4, TiB2, TiN, TiC), graphite and diamond. The chemical composition of the powders was studied by X-ray microprobe and various other methods, and BET specific areas were determined. The haemolysis was almost zero for all powders, except AlN which showed slight haemolysis and TiB2 which had high haemolytic power.

Haemocompatibility of Ti6A14V alloy.

Ti6A14V alloy has been mainly used as a biomaterial in the orthopaedic field. The present study describes the surface state of the Ti6A14V material and evaluates its in vitro haemocompatibility in terms of protein adsorption, platelet retention and haemolysis. The behaviour of the Ti6A14V alloy towards albumin and fibrinogen was compared to that of a reference medical-grade elastomer. The platelet retention test gave better results than those achieved with the elastomer. The haemolysis percentage of the alloy was almost zero. These results indicate that the Ti6A14V alloy is well tolerated by blood.

A New Model to Test Platelet Adhesion under Dynamic Conditions: Application to the Evaluation of a Titanium Nitride Coating

In order to evaluate under dynamic circumstances the in vitro platelet adhesion induced by rigid materials such as ceramic coatings deposited on selected substrates, a new model simulating a tube has been designed. In vitro platelet adhesion was assessed with this new model: the material was titanium nitride (TiN) deposited on Ti6A14V (TA6V) titanium alloy by a physical vapor deposition (PVD) process. The results were compared to those obtained with complete titanium carbide (TiC) graphite tubes coated with TiN by a chemical vapor deposition (CVD) process. The difference observed (less than 25%) in favour of the new system, could be due to the better surface state of the construction materials of this system. In fact it is a systemic error. However TiN confirms its good performance as a blood-contacting biomaterial.

Physico-chemistry and cytotoxicity of ceramics: Part I – Characterization of ceramic powders

The morphology of Al2O3, ZrO2/Y2O3, AIN, B4C, BN, SiC, Si3N4, TiB2, TiC, TiN ceramic, graphite and diamond powders has been studied by scanning electron microscopy (SEM) and the specific area of each powder was determined with the BET method. X-ray diffraction (XRD) investigations have been carried out in order to evaluate the crystallinity and determine the constitutive phases. The chemical composition was assessed by classical chemical analyses and by X-ray microprobe; some powders were studied by the laser micro-Raman technique. Correlations have been established between all these results.

Complement Activation by Ceramics

The left ventricular assist device is based on the principle of the Maillard-Wenkel rotative pump. The materials which make up the pump must present particular mechanical, tribological, thermal and chemical properties. Graphite has been selected as a substrate, ceramic as the coating. The purpose of this study is to evaluate the in vitro complement activation eventually initiated by ceramic powders (A12O3, ZrO2/Y2O3, AIN, B4C, BN, SiC, Si3N4, TiB2, TiC, TiN), graphite and diamond. The morphology of powders has been studied by Scanning Electron Microscopy and X-Ray Diffraction investigations have been carried out. The evaluation of complement activation was undertaken by measuring the total hemolytic complement (CH50). No activation has been detected.

TiN coating: Physico-chemistry and leukocyte adhesion

The left ventricular assist device under consideration in this paper is based on the principle of the Maillard-Wenkel rotary pump. Construction materials must meet stringent requirements. Titanium Nitride (TiN) has been chosen for its surface properties. The purpose of this study was to characterize the Physical Vapor Deposition (PVD) TiN coating, to evaluate in vitro leukocyte adhesion and to confront these results. The surface state results were similar; leukocyte adhesion was low but twice larger on TiN than on the reference medical grade elastomer.