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[8a-PA1-10] Development of surface-fluorinated tetrahedral amorphous carbon with antithrombotic and wear resistant properties for ventricular artificial heart
Keywords:amorphous carbon films, biomaterials, surface treatment
Introduction
Blood-contacting medical devices with sliding/rotating parts such as ventricular assist devices (VAD) have attracted attention for reducing the mortality rates of cardiovascular diseases. However, thrombus formation and abrasive wear can trigger the life-threating device failure. To improve these problems, development of materials with both antithrombogenicity and wear resistance is required. Surface coating is one of the most effective methods of improving surface properties for medical devices. Recently, fluorine-incorporated hydrogenated amorphous carbon (a-C:H:F) have received much attention because of their antithrombotic properties derived from C-F bonds of their topmost surface. However, doping fluorine to amorphous carbon changes internal carbon structure from diamond-like to polymer-like structure, which results in low wear resistant properties. Thus, we newly synthesized surface-fluorinated tetrahedral amorphous carbon (ta-C) with fluorocarbon plasma treatment focused on both antithrombogenicity with surface C-F bonding and wear resistance with diamond-like carbon characteristics of ta-C.
Materials and Methods
The ta-C film was deposited by filtered cathodic vacuum arc method using a graphite target. The ta-C surface was fluorinated by fluorocarbon gases with a capacitively coupled radio-frequency (13.56) MHz plasma. The surface treatment was performed at RF power of 200W for 10, 20 and 30 secs, respectively. The fluorine content of the film surfaces was measured by X-ray photoelectron spectroscopy. Carbon bonding structure was analyzed with Raman spectroscopy. Antithrombogenicity were evaluated by human platelets adsorption tests, and wear resistance by ball-on-disk tests.
Results and Discussion
The fluorine content rate of each surface-fluorinated ta-C film was approximately 25 at. % regardless of plasma treatment time. Raman spectra of each sample did not change in each treatment time, which means that surface-fluorination did not affect the internal carbon structure of ta-C. These results indicate that fluorocarbon plasma doped fluorine to ta-C surface without changing internal carbon bonding structure. Platelets adhesion could be significantly reduced on the surface-fluorinated ta-C compared with that on the non-treated ta-C (P < 0.05). On the other hand, the numbers of adherent platelets were not changed by plasma treatment time. No wear track was observed in all samples after ball-on-disk tests. This result indicates that surface-fluorinated ta-C has great wear resistant properties equivalent to the properties of non-treated ta-C.
Conclusion
We succeeded in developing the new films which show both excellent antithrombogenicity and wear resistance by treating the ta-C surface using a fluorocarbon plasma. The surface-fluorinated ta-C can be a promising candidate for sliding parts of blood-contacting medical devices, such as a VAD.
Blood-contacting medical devices with sliding/rotating parts such as ventricular assist devices (VAD) have attracted attention for reducing the mortality rates of cardiovascular diseases. However, thrombus formation and abrasive wear can trigger the life-threating device failure. To improve these problems, development of materials with both antithrombogenicity and wear resistance is required. Surface coating is one of the most effective methods of improving surface properties for medical devices. Recently, fluorine-incorporated hydrogenated amorphous carbon (a-C:H:F) have received much attention because of their antithrombotic properties derived from C-F bonds of their topmost surface. However, doping fluorine to amorphous carbon changes internal carbon structure from diamond-like to polymer-like structure, which results in low wear resistant properties. Thus, we newly synthesized surface-fluorinated tetrahedral amorphous carbon (ta-C) with fluorocarbon plasma treatment focused on both antithrombogenicity with surface C-F bonding and wear resistance with diamond-like carbon characteristics of ta-C.
Materials and Methods
The ta-C film was deposited by filtered cathodic vacuum arc method using a graphite target. The ta-C surface was fluorinated by fluorocarbon gases with a capacitively coupled radio-frequency (13.56) MHz plasma. The surface treatment was performed at RF power of 200W for 10, 20 and 30 secs, respectively. The fluorine content of the film surfaces was measured by X-ray photoelectron spectroscopy. Carbon bonding structure was analyzed with Raman spectroscopy. Antithrombogenicity were evaluated by human platelets adsorption tests, and wear resistance by ball-on-disk tests.
Results and Discussion
The fluorine content rate of each surface-fluorinated ta-C film was approximately 25 at. % regardless of plasma treatment time. Raman spectra of each sample did not change in each treatment time, which means that surface-fluorination did not affect the internal carbon structure of ta-C. These results indicate that fluorocarbon plasma doped fluorine to ta-C surface without changing internal carbon bonding structure. Platelets adhesion could be significantly reduced on the surface-fluorinated ta-C compared with that on the non-treated ta-C (P < 0.05). On the other hand, the numbers of adherent platelets were not changed by plasma treatment time. No wear track was observed in all samples after ball-on-disk tests. This result indicates that surface-fluorinated ta-C has great wear resistant properties equivalent to the properties of non-treated ta-C.
Conclusion
We succeeded in developing the new films which show both excellent antithrombogenicity and wear resistance by treating the ta-C surface using a fluorocarbon plasma. The surface-fluorinated ta-C can be a promising candidate for sliding parts of blood-contacting medical devices, such as a VAD.