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. 23-27, San Diego, USA

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

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.

Si-DLC Film Potentiodynamic Polarization Purpose of the present work Potentiodynamic Polarization Thin Solid Films, 475, 291-397 (2005)

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. 128-129 (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.

Surface modification of Si-DLC Purpose of the present work

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.

Surface modification of Si-DLC Purpose of the present work

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

Surface Energy

Polar Component and Wetting

Interfacial Tension with Human Blood α (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

XPS Anaysis

Single bond C-C increased C-F bond increase _ _ Single bond C-C increased C-F bond increase Si-C bond Si-O bond

N1 : Si-N N2 : C=N

_ _

XPS Anaysis

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

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.

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

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

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 email.  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.

Platelets on Si-DLC

Platelets on Si-DLC (CF4)

Platelets on Si-DLC (N2)

Platelet on Si-DLC (O2)

Nitrogen or Oxygen Plasma Treatment

Interfacial 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. 128-129 (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)

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

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 #: 06K1501-01610), and Taewoong Medical Co. Ltd.