Hemocompatibility of Surface Modified Diamondlike Carbon Coatings R
Hemocompatibility of Surface Modified Diamond-like Carbon Coatings R. K. Roy, M. -W. Moon, K. -R. Lee Future Technology Research Laboratories, KIST, Seoul, Korea D. K. Han Biomaterials Research Center, KIST, Seoul, Korea J. -H. Shin Department of Radiology, Asan Medical Center, Universtiy of Ulsan, Korea A. Kamijo Univ. Tokyo Hospital, Tokyo, Japan T. Hasebe Tachikawa Hospital, Keio University, Tokyo, Japan ABMC 2007, Tsukuba, 2007. 12. 6.
Bioimplant Materials Requirements for Bioimplants 1. 2. 3. 4. Should not cause infections Prevent uncontrolled cell growth Maintain their integrity inside the body Interact in a controllable way with the biological environment 5. Avoid formation of debris Surface Properties
Required Surface Properties • Biological Compatibility – Nontoxic, Noncarcinogenic, Noninflammatory • Chemical Compatibility – Corrosion Resistance • Mechanical Compatibility – Surface Hardness, Wear Resistance Diamond-like Carbon : as a Strong Candidate Coating
Vascular Stents Clotted Artery • Formation of blood clots Restenosis • Release of metal ions Hemocompatible and Hermetic Coating
DLC Coated Blood Contacting Implants Carbofilm. TM by Sorin Biomedica, Inc.
DLC is sufficiently hemocompatible? • DLC film is not a specific material but a group of amorphous carbon thin films. For each application, we need to optimize the property. Understanding of hemocompatibility of various DLC surfaces Si incorporated DLC films with modified surface
Si-DLC Film Potentiodynamic Polarization in Saline Solution Thin Solid Films, 475, 291 -397 (2005). J. Biomed. Mater. Res. A in press (2007).
Film Preparation • Film Deposition – – – C 6 H 6 + Si. H 4 Pressure : 1. 33 Pa Bias voltage : -400 V Film thickness : ~500 nm Si Concentration in the film : 2 at. % • Surface Treatment Schematic diagram of RF PACVD system. – – O 2, N 2, H 2, CF 4 Pressure : 1. 33 Pa Bias voltage : -400 V 10 min
Surface modification of Si-DLC
Energetics of Surface q Liquid αl βl γlv (ergs/cm 2) Water 4. 67 7. 14 72. 8 Formamide 6. 28 4. 32 58. 2
Surface Energy
Polar Component and Wetting CF 4 plasma As deposited H 2 plasma Si wafer N 2 plasma O 2 plasma
Interfacial Tension with Human Blood α (dyne/cm)1/2 β (dyne/cm)1/2 3. 3 6. 0 α β Si-DLC 5. 4 ± 0. 5 3. 3 ± 0. 6 Si-DLC (CF 4 treated) 5. 0 ± 0. 4 2. 0 ± 0. 5 Si-DLC (N 2 treated) 5. 1 ± 0. 2 5. 5 ± 0. 3 Si-DLC (O 2 treated) 4. 2 ± 0. 1 7. 3 ± 0. 1 Si-DLC (H 2 treated) 5. 5 ± 0. 3 3. 5 ± 0. 4 Human Blood
XPS Anaysis
N 1 : Si-N N 2 : C=N
XPS Anaysis
XPS Analysis Films Chemical bonds present on surface (XPS analysis) Si-DLC or Si-DLC (H plasma treated) C=C, C-C, Si-O Si-DLC (CF 4 plasma treated) C=C, C-CFn, Si-C, Si-O Si-DLC (N plasma treated) C=C, C-N, Si-O Si-DLC (O plasma treated) C=C, C-O, Si-O
a. PTT Measurement • • Activated partial thromboplastin time (a. PTT) determines the ability of blood to coagulate through the intrinsic coagulation mechanism. Soaking for 60 min in platelet poor plasma (PPP: 7 x 103/ml) using human whole blood from healthy volunteer.
Plasma Protein Adsorption • • ELISA analysis after treating the samples with albumin (3 mg/ml) and fibrinogen (0. 2 mg/ml) solution. Better hemocompatibility can be expected on the surface with higher ratio of albumin/fibrinogen adsorption.
Platelet Adhesion Measurement • • Soaked for 60 min in PRP (1. 5 x 1015/ml) from human whole blood from healthy volunteer. Adherent platelet are fixed and dehydrated for observation under OM and SEM.
Platelet Activation Goodman and Allen et al. Lose discoid shape Develope thin pseudopodia On a-C: H surface Become large, spiny sphere covered by Pseudopodia Fully spread
Platelets on Si-DLC
Platelets on Si-DLC (N 2)
Platelet on Si-DLC (O 2)
Nitrogen or Oxygen Plasma Treatment
Hemocompatibility and the Surface Sl. No. References Hemocompatibility Improves by 1 Baier, Academic Press, New York, 1970. Critical surface tension of materials ~ 20 -30 dyne/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) Kwok, Diam. Rel. Mater. 14 (2005) 78. interfacial tension of about the same magnitude as cell-medium interfacial tension (1 -3 dyne/cm) 6
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 • Aging of the surface with large surface energy should be carefully considered in characterizing their surface properties. Characterization should be done within 12 hours after the treatment.
Acknowledgement Financial Support from 'Center for Nanostructured Materials Technology' under '21 st Century Frontier R&D Programs' of the Ministry of Science and Technology of Korea (code #: 06 K 1501 -01610), and Taewoong Medical Co. Ltd.
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