Thrombogenesis is the principal problem associated with blood-contacting biomedical devices. One of the important reasons is that most of the materials used in these devices cannot avoid inducing platelet adhesion and activation. Our recent investigation suggested that Ti-O thin film could be an alternative antithrombotic material. In this work, we focus our attention on behavior of platelets adhered on Ti-O film. Platelet adhesion experiments were conducted to examine the platelets/material interaction in vitro and the effect of protein adsorption on platelet adhesion and activation. The specific resultants of platelet release (GMP140) were tested for evaluating the platelet activation. In vivo implantation was used to investigate formation of thrombus. The excellent anticoagulation performance of Ti-O films has been shown in in vivo long-term mplantation. The release of specific resultants GMP140 from platelets contacting to Ti-O film was the lower than LTI-carbon. The morphology of adherent platelets maintainsround and isolated. Apparently, the activation of platelets adhered on Ti-O film was suppressed. The results of in vitro test also suggest that the suppression of platelet activation is related to plasma protein adsorption. Preadsorbing fibrinogen doesn't cause the exacerbation of platelet activation. It seems reasonable to suggest that its excellent anticoagulation is caused by inhibition of adherent platelet activation produced by Ti-O film.

Nitrogen incorporated carbon films were synthesized using plasma immersion ion implantation and deposition at room temperature. Nitrogen partial pressure was varied from 1.0

Surface modification has become a important field in biomaterials research because of the low cost, the high efficacy and the versatility. In this paper some recent applications of surface modification technology on the materials for cardiovascular devices were provided. Three ategories of the surface modification process, biological molecular immobilization, chemical medium binding and energy carrier substances coating or modification are discussed, the authors series work on the surface modification of artificial heart valve and vascular stents etc. are presented. The further development of the field is also discussed.

TiN and Ti-O/TiN films have been deposited on Ti-6Al-4V substrate using plasma immersion ion implantation and deposition (PIII&D). It has been proved that TiN and Ti-O/TiN films both enhance the corrosion resistance of substrate materials. Potentiodynamic polarization curves show that both Ti-6Al-4V substrates deposited with these two kinds of films have lower dissolution urrents than that of the uncoated one. Electrochemical impedance spectroscopy (EIS) measurements indicates that TiN films with high corrosion resistance is mainly due to its barrier-type dense film layer, and that Ti-O/TiN film provides high corrosion resistance is mainly owing to its high corrosion potential (Ecorr). Friction coefficient curves obtained from pin-on-disk wear tests, as well as following SEM observation of wear residual trace width and morphology, indicate that TiN and Ti-O/TiN films both present high wear resistance in comparison with uncoated Ti-6Al-4V.

In the present paper, the scientific basis, technique approaches, the present status and the development trends of surface modification for blood contacting materials are discussed briefly. The work in authors' Lab. is also presented.

The present paper presents the results of surface modifications of biomaterials using plasma immersion ion implantation (PIII) in Institute of Surface Modification of Biomaterials in Southwest Jiaotong University. In the research, titanium oxide films and diamond-like carbon (DLC) films doped with different elements, as well as surface modification of polymers, are prepared using PIII. The blood compatibility of the films is investigated. Significant improvement in blood compatibility of the films compared with those untreated substrate materials is confirmed. The mechanisms of the blood compatibility of the films are discussed. The results show that the energy band structure of the material surface may be a controlling factor in the blood compatibility of the material. A film with an n-type semiconductor nature would have a better blood compatibility. Improvement in wear resistance of hip joint and modification of antibacterial property of artificial heart valve suture ring material is also presented in the paper.

Over the past decade, much attention has been paid to anti-thrombotic materials applied in artificial organs. Surface modification has shown potential to improve the anti-coagulation of blood-contacting biomedical devices and materials w1-3x. Our in vitro study of Ti-O thin films has recently shown that Ti-O thin films possess superior blood compatibility to low temperature isotropic pyrolytic carbon (LTI-carbon), w1x. In this work, we have focussed our attention onto the in vivo evaluation of Ti-O thin films fabricated by plasma immersion ion implantation (PIII). The samples of titanium coated by Ti-O thin films were implanted in dogs'hearts for 1 month. The results of the implantation showed that no thrombus was found on the surfaces of the Ti-O thin film, although the coagulation occurred on the surfaces of LTI-carbon.

Hemocompatibility is a key property of biomaterials that come in contact with blood. Surface modification has shown great potential for improving the hemocompatibility of biomedical materials and devices. In this paper, we describe our work of improving hemocompatibility with Ti-O thin films prepared by plasma immersion ion implantation and deposition and by sputtering. The structure and surface chemical and physical properties of the films were characterized by X-ray diffraction, Auger electron spectroscopy, atomic force microscopy (AFM), contact angle measurement, and Hall effect measurement. The behavior of fibrinogen adsorption was investigated by 125I radioactive isotope labeling and AFM. Systematic evaluation of hemocompatibility, including in vitro clotting time, thrombin time, prethrombin time, platelet adhesion, and in vivo implantation into dog's ventral aorta or right auricle from 17 to 90 days, proved that Ti-O films have excellent hemocompatibility. It is suggested that the significantly lower interface tension between Ti-O films and blood and plasma proteins and the semiconducting nature of Ti-O films give them their improved hemocompatibility.

Plasma immersion ion implantation and deposition (PIIID) provides a novel approach to fabricate high quality films by means of utilizing particle filtrated metal plasma and varying acceleration pulse voltages. In this work, investigation on plastic deformation of TiN films synthesized by PIIID was performed by pulling the TiN film-coated stainless steel sheet samples. The surface morphology during the pulling was observed in situ by scanning electron microscopy. No elaminating, peeling or cracking werefound on the coating surfaces. The structure of the films was identified by transmission electron microscopy and atom force microscopy. It is considered that the excellent deformation behavior of the TiN film was related with the nanocrystal structure of the films and the broader filmymatrix interface achieved by the PIII process.

Titanium oxide films were synthesizedon titianium, cobalt alloy and low-temperature istropic pryolytic carbn by ion beam enhanced deposition. The non-stoichiometrical titanium oxide films were obtained. Blood compatibility of the films were evaluated by clotting time measurement, platelet adhesion in vestigation and hemlysis analyses. The results revealed that blood compatibility of the materials was improved by the coating of titanium oxide films. Semiconductor natute fo non-stoichiometric titanium oxide films might be responsible ofor the improvement of blood compatibility.