1. R. K. Roy, S.-J. Park, H.-W. Choi, K.-R. Lee
Hemocompatibility of Surface Modified Si Incorporated Diamond-like Carbon Films
R. K. Roy, S.-J. Park, H.-W. Choi, K.-R. Lee
Future Technology Research Laboratories, KIST, Seoul, Korea
T. Hasebe
Tachikawa Hospital, Keio University, Tokyo, Japan
ICMCTF-2007, Apr , San Diego, USA

2. Hemocompatible and Hermetic Coating
Vascular Stents
Clotted Artery
Formation of blood clots  Restenosis
Release of metal ions
A stent is a metal tube that is inserted permanently into an artery. The stent helps open an clotted artery so that blood can flow through it. The cardiovascular implantation of stents is increasing day by day throughout the world. But the application of stents is largely limited by restenosis, occlusion and stent associated thrombosis. The main side effect with artery stents lies in its release of metal ions and thrombogenicity. It is thus necessary to coat metallic stents with suitable biomaterial that are hemocompatible, corrosion resistant and long lasting in human blood environment.
Hemocompatible and Hermetic Coating

3. Surface Modification
Biocompatible Coating : Heparin, PEG, DLC (Hepacoat, Phytis)
Drug Release Coating : Antistenosis, Anticancer, Antibiotic (Cordis)
Isotope Radiation Coating : Radiation therapy
Many coated stents are already found in the market. Heparin, PEG and DLC films are coated on the stent to meet the requirements of the hemocompatible surface. DLC coating can suppress the metal release in addition to the hemocompatiblility. This figure shows the DLC coated stent. More active concept is to use the drug release coating for antistenosis and treatment such as anticancer or antibiotic. There is also isotope radiation coating for radiation therapy.
This presentation is about the DLC application for these purpose.

4. Si-DLC Film Potentiodynamic Polarization
Purpose of the present work
Potentiodynamic Polarization
Thin Solid Films, 475, (2005)

5. Hemocompatibility and Surface Tension
Sl.
No.
References
Hemocompatibility
Improves by 1
Baier,
Academic Press,
New York, 1970.
Critical surface tension of materials
~ 20-30dyne/cm 2
Akers,
J.Colloid Interface Sci.
59 (1977) 461.
Zone of biocompatibility 3
Ruckensten & Gourisanker,
J. Colloid Interface Sci. 101
(1984) 436.
Blood biomaterial interfacial tension of
the order of 1-3 dyne/cm 4
Callow,
International Biodeterioration & degradation, 34 (1994) 333.
Surfaces having initial surface tension
20-30 dyne/cm 5
Yu,
Surf. Coat. Technol.
(2000) 484.
Low blood biomaterial interfacial tension
(8.5 dyne/cm) 6
Kwok,
Diam. Rel. Mater. 14 (2005) 78.
interfacial tension of about the same magnitude as cell-medium interfacial tension
(1-3 dyne/cm)
In the view point of hemocompatibility, most previous works focused on the surface because all biological reaction occurs on the surface of biomaterials. Here are some results on the relationship between the hemocompatibility and the surface energy. Some people suggested that higher surface tension is favorable while others insist that
However, these data cannot be compared directly, because they apply very different kind of DLCs.
The purpose of the present work is to study on the relationship but in more systematic way. For these purpose, we modified the surface of the same DLC films by plasma.

6. Surface modification of Si-DLC
Purpose of the present work

7. Film Preparation Film Deposition Surface Treatment C6H6 + SiH4
Pressure : 1.33 Pa
Bias voltage : -400V
Film thickness : ~500nm
Si Concentration in the film : 2 at.%
Surface Treatment
O2, N2, H2, CF4
10min
Schematic diagram of RF PACVD system.

8. Surface modification of Si-DLC
Purpose of the present work

9. Energetics of Surface q Liquid αl βl γlv (ergs/cm2) Water 4.67 7.14
72.8
Formamide
6.28
4.32
58.2

10. Surface Energy

11. Polar Component and Wetting

12. Interfacial Tension with Human Bloodα
(dyne/cm)1/2 β
Human
Blood
3.3
6.0 α β
Si-DLC
5.4 ± 0.5
3.3 ± 0.6
(CF4 treated)
5.0 ± 0.4
2.0 ± 0.5
(N2 treated)
5.1 ± 0.2
5.5 ± 0.3
(O2 treated)
4.2 ± 0.1
7.3 ± 0.1
(H2 treated)
3.5 ± 0.4

13. XPS Anaysis

14. Single bond C-C increased C-F bond increase_ _
Single bond C-C increased
C-F bond increase
Si-C bond Si-O bond

15. N1 : Si-N
N2 : C=N

16. _ _

17. XPS Anaysis

18. Chemical bonds present on surface
XPS Analysis
Films
Chemical bonds present on surface
(XPS analysis)
Si-DLC
C=C, C-C, Si-C, Si-O
(CF4 plasma treated)
C=C, C-C, C-CFn, Si-C, Si-O
(N plasma treated)
C=C, C-C, C-N, Si-N, Si-O
(H plasma treated)
(O plasma treated)
C=C, C-C, C-O, Si-O

19. aPTT Measurement
Soaking for 60min in platelet poor plasma (PPP: 7x103/ml) using human whole blood from healthy volunteer
aPTT measurement system by Sysmex Instrument
Activated partial thromboplastin time (aPTT) determines the ability of blood to coagulate through the intrinsic coagulation mechanism.
It measures the clotting time from the activation of the factor XII through the formation of fibrin clot.

20. Plasma Protein Adsorption
Done by treating the samples with albumin (3mg/ml) and fibrinogen (0.2mg/ml) solution.
ELISA analysis method to characterize the proten adsorption

21. Platelet Adhesion Measurement
PRP (1.5x1015/ml) from human whole blood from healthy volunteer
Soaked in PRP for 60min
Adherent platelet are fixed and dehydrated for observation under OM and SEM

22. Platelets on Surface On a-C:H surface Goodman and Allen et al.
The morphological shape changes were categorized to Goodman and Allen et al. (Category 1 to 5).  Early platelet activation produces cytoskeletal reorganization that results in characteristic cell shape changes: platelets lose their discoid shape and begin to develop thin pseudopodia. At more advanced stages, they become large, spiny spheres completely covered by pseudopodia, and finally, become fully spread.  Please find the attached figure with this .  In our study, using computer-aided image analysis, the number of adherent platelets and platelet-covered area were determined as markers of surface thrombogenicity. Both the number of platelets and the changes in morphological shape in active platelets contribute to the platelet-covered surface area of the substrate. Thus, calculating the platelet-covered area/unit area is an index that reflects platelet adhesion and activation.
Goodman and Allen et al.

23. Platelets on Si-DLC

24. Platelets on Si-DLC (CF4)

25. Platelets on Si-DLC (N2)

26. Platelet on Si-DLC (O2)

27. Nitrogen or Oxygen Plasma Treatment

28. Interfacial Tension? Sl. No. References Hemocompatibility Improves by1
Baier,
Academic Press,
New York, 1970.
Critical surface tension of materials
~ 20-30dyne/cm 2
Akers,
J.Colloid Interface Sci.
59 (1977) 461.
Zone of biocompatibility 3
Ruckensten & Gourisanker,
J. Colloid Interface Sci. 101
(1984) 436.
Blood biomaterial interfacial tension of
the order of 1-3 dyne/cm 4
Callow,
International Biodeterioration & degradation, 34 (1994) 333.
Surfaces having initial surface tension
20-30 dyne/cm 5
Yu,
Surf. Coat. Technol.
(2000) 484.
Low blood biomaterial interfacial tension
(8.5 dyne/cm) 6
Kwok,
Diam. Rel. Mater. 14 (2005) 78.
interfacial tension of about the same magnitude as cell-medium interfacial tension
(1-3 dyne/cm)

29. Conclusions
Hemocompatibility of Si-DLC film would be improved by surface treatment using nitrogen and oxygen plasma.
Large surface energy (large polar component)
Low interfacial energy with blood

30. Acknowledgement
Financial Support from 'Center for Nanostructured Materials Technology' under '21st Century Frontier R&D Programs' of the Ministry of Science and Technology of Korea (code #: 06K ), and Taewoong Medical Co. Ltd.