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Hemocompatibility of Plasma Treated Si
Incorporated Diamond-like Carbon Films
R. K. Roy, M.-W. Moon, K.-R. LeeFuture Convergence Research Laboratories, KIST, Seoul, Korea
D.K. HanBiomaterials Research Center, KIST, Seoul, Korea
J.-H. ShinDepartment of Radiology, Asan Medical Center, Universtiy of Ulsan, Korea
A. KamijoUniv. Tokyo Hospital, Tokyo, Japan
T. HasebeTachikawa Hospital, Keio University, Tokyo, Japan
ICMCTF 2008, San Diego, USA
Requirements for Bioimplants1. Should not cause infections2. Prevent uncontrolled cell growth3. Maintain their integrity inside the
body4. Interact in a controllable way with
the biological environment
5. Avoid formation of debris
Requirements for Bioimplants1. Should not cause infections2. Prevent uncontrolled cell growth3. Maintain their integrity inside the
body4. Interact in a controllable way with
the biological environment
5. Avoid formation of debris
Surface PropertiesSurface Properties
Bioimplant Materials
DLC for biomaterials
• 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
• Suppress the formation of blood clots• Prevent the release of metal ions
Clotted Artery
Hemocompatible and Hermetic Coating
DLC Coated Blood Contacting Implants
CarbofilmTM by Sorin Biomedica, Inc.
The present work
Systematic study on the effect of surface properties on the hemocompatibility.
• Plasma treatment of Si-DLC coating• Characterization of the surface
– Wetting behavior– Surface chemical bonds
• Hemocompatibility tests– Protein adsorption (Albumin/Fibrinogen
ratio)– Activated Partial Thromboplastin time– Platelet adhesion and activation
Si-DLC Film
10-14 10-13 10-12 10-11 10-10 10-9 10-8 10-7 10-6 10-5 10-4 10-3 10-2 10-1 100 101
-600
-400
-200
0
200
400
600
800
1000
1200
1400
1600
Po
ten
tial (
mV
vs
SC
E)
Current Density (A/cm2)
Substrate Si-C:H, Bias voltage = -400V a-C:H, Bias voltage = -800V a-C:H, Bias voltage = -400V
Potentiodynamic Polarization in Saline Solution
Thin Solid Films, 475, 291-397 (2005).J. Biomed. Mater. Res. A in press (2007).
Schematics of RF PACVD system.
Film Preparation
• Film Deposition– 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
– Pressure : 1.33 Pa– Bias voltage : -400V– 10min
Surface modification of Si-DLC
20
40
60
80
100W
ater
co
nta
ct a
ng
le (
in d
egre
e)
SiDLC( O2treated)
SiDLC(N2treated)
SiDLC(H2treated)
SiDLC(CF4treated)
SiDLCSi Nitinol
Energetics of Surface
(cos ) lv sv sl
22ll
pl
dllv
22ss
ps
dssv
)(2
cos1
)(2)(2cos1
lslslv
lv
pl
ps
lv
dl
ds
Liquid αl βl
γlv
(ergs/cm2)
Water 4.67 7.14 72.8
Formamide 6.28 4.32 58.2
2 : Fowkes' Eq.d dsl sv lv s l
Surface Energy
Polar component
0
10
20
30
40
50
60
SiDLC SiDLC (O
2
treated)
SiDLC (N
2
treated)
SiDLC (H
2
treated)
SiDLC (CF4
treated)
Sur
face
ene
rgy
(dyn
e/cm
)
Dispersive component
Interfacial Tension with Human Blood
α (dyne/cm)1/2
β (dyne/cm)1/2
Human Whole Blood
3.3 6.0
221
22112 )()(
0
5
10
15
20
25
SiDLC(O2
treated)
SiDLC(N2
treated)
SiDLC(H2
treated)
Blo
od B
iom
ater
ial i
nter
faci
al t
ensi
on
(dyn
e/cm
)
SiDLC SiDLC(CF4
treated)
α β
Si-DLC 5.4 ± 0.5 3.3 ± 0.6
Si-DLC (CF4 treated) 5.0 ± 0.4 2.0 ± 0.5
Si-DLC (N2 treated) 5.1 ± 0.2 5.5 ± 0.3
Si-DLC (O2 treated) 4.2 ± 0.1 7.3 ± 0.1
Si-DLC (H2 treated) 5.5 ± 0.3 3.5 ± 0.4
100 102 104 106
4
8
12
16
Inte
nsi
ty (
x1
0 )
Binding energy (eV)
Si-C
Si 2pSiDLC
Si2O3
SiO2
(b)
280 284 288 2920
10
20
30
40
50
Inte
nsi
ty (
x1
0 2
)
Binding energy (eV)
C=C
C-C
Si-DLC
C 1s(a)
280 284 288 2920
10
20
30
40
Inte
nsity
( x
10
2 )
Binding energy (eV)
C=C
C-CC-OH
H2-Si-DLC
C 1s(c)
100 102 104 106
4
8
12
16
Inte
nsity
( x
10 )
Binding energy (eV)
Si-C
Si-Si
Si2O3
Si 2pH2-Si-DLC(d)
XPS Anaysis
XPS Analysis
FilmsChemical bonds present on surface
(XPS analysis)
Si-DLC or Si-DLC (H plasma
treated)C=C, C-C, Si-C, Si-O
Si-DLC(CF4 plasma treated)
C=C, C-C, C-CFn, Si-C, Si-O
Si-DLC(N plasma treated)
C=C, C-C, C-N, Si-N, Si-O
Si-DLC(O plasma treated)
C=C, C-C, C-O, Si-O
100 102 104 106
4
8
12
16
Inte
nsi
ty (
x1
0 )
Binding energy (eV)
Si-C
Si 2pSiDLC
Si2O3
SiO2
(b)
280 284 288 2920
10
20
30
40
50
Inte
nsi
ty (
x1
0 2
)
Binding energy (eV)
C=C
C-C
Si-DLC
C 1s(a)
XPS Anaysis
280 284 288 2920
4
8
12
16
Inte
nsi
ty (
x1
0 2 )
Binding energy (eV)
C=C
C-C C-O C=O
C 1sO2-Si-DLC(k)
100 102 104
20
40
60
80
Inte
nsi
ty (
x10
)
Binding energy (eV)
Si 2pO2-Si-DLC
Si2O3
SiO2
Si-C
(l)
280 284 288 2920
5
10
15
20
25
Inte
nsi
ty (
x1
0 2 )
Binding energy (eV)
C-CFn
CF-CFnCF2 CF3
1
2
C 1sCF4-Si-DLC(e)
100 102 104 106
4
6
8
10
Inte
nsi
ty (
x 1
0 )
Binding energy (eV)
Si-C
Si2O3
SiO2
Si-Si
Si 2pCF4-Si-DLC(f)
Si-DLC Si-DLC (CF4)Si-DLC (O2)
100 102 104 106
5
10
15
20
25
Inte
nsi
ty (
x10
)
Binding energy (eV)
Si-N
Si-CSiO2
Si 2pN2-Si-DLC(i)
280 284 288 2920
5
10
15
20
25
Inte
nsity
( x
10
2 )
Binding energy (eV)
C 1sN2-Si-DLCC=C
C=N
C=N
C-C
C-N
(h)
100 102 104 106
4
8
12
16
Inte
nsi
ty (
x1
0 )
Binding energy (eV)
Si-C
Si 2pSiDLC
Si2O3
SiO2
(b)
280 284 288 2920
10
20
30
40
50In
tens
ity (
x10
2 )
Binding energy (eV)
C=C
C-C
Si-DLC
C 1s(a)
Si-DLC Si-DLC (N2)
XPS Anaysis
Plasma Protein Adsorption
• Better hemocompatibility can be expected on the surface with higher ratio of albumin/fibrinogen adsorption.
• ELISA analysis after treating the samples with albumin (3mg/ml) and fibrinogen (0.2mg/ml) solution.
0.0
0.5
1.0
1.5
2.0
SiDLC (H2
treated)
SiDLC(O2
treated)
SiDLC(N2
treated)
SiDLC (CF4
treated)
SiDLC
Alb
umin
/ f
ibri
noge
n ra
tio
5 mins
60 mins
aPTT Measurement
• Activated partial thromboplastin time (aPTT) determines the ability of blood to coagulate through the intrinsic coagulation mechanism. The longer aPTT time is obtained on better hemocompatible surface.
• Soaking for 60min in platelet poor plasma (PPP: 7x103/l) using human whole blood from healthy volunteer.
25
26
27
28
29
30
SiDLC(O2
treated)
SiDLC(N2
treated)
SiDLC(H2
treated)
SiDLC(CF4
treated)
aPT
T (
sec)
1 hour
Platelet Adhesion Measurement
• Soaked for 60 min in PRP (1.5x105/ml) from human whole blood from healthy volunteer.
• Adherent platelet are fixed and dehydrated for observation under OM and SEM.
Si-DLC Si-DLC(CF4) Si-DLC(N2) Si-DLC(O2)0
10
20
30
40
50
60
70
80
90
100
Pla
tele
t Ad
he
sio
n A
rea
Ra
tio (
%)
Specimen
Platelet Activation
Goodman and Allen et al.
On a-C:H surface
Lose discoid shape
Develope thin pseudopodia
Become large, spiny sphere covered by pseudopodia
Fully spread
Platelets on Si-DLC
Platelets on Si-DLC (N2)
Platelet on Si-DLC (O2)
Nitrogen or Oxygen Plasma Treatment
25
26
27
28
29
30
SiDLC(O2
treated)
SiDLC(N2
treated)
SiDLC(H2
treated)
SiDLC(CF4
treated)
aPT
T (
sec)
1 hour
0.0
0.5
1.0
1.5
2.0
SiDLC (H2
treated)
SiDLC(O2
treated)
SiDLC(N2
treated)
SiDLC (CF4
treated)
SiDLC
Alb
umin
/ fib
rinog
en r
atio
5 mins
60 mins
Si-DLC Si-DLC(CF4) Si-DLC(N2) Si-DLC(O2)0
10
20
30
40
50
60
70
80
90
100
Pla
tele
t A
dh
esi
on
Are
a R
atio
(%
)
Specimen
XPS Analysis
FilmsChemical bonds present on surface
(XPS analysis)
Si-DLC or Si-DLC (H plasma
treated)C=C, C-C, Si-C, Si-O
Si-DLC(CF4 plasma treated)
C=C, C-C, C-CFn, Si-C, Si-O
Si-DLC(N plasma treated)
C=C, C-C, C-N, Si-N, Si-O
Si-DLC(O plasma treated)
C=C, C-C, C-O, Si-O
Which surface bond is significant?
Conclusions
• Hemocompatibility of Si-DLC film was improved by the surface treatment using nitrogen and oxygen plasma.– Large surface energy (large polar component)– Low interfacial energy with blood
• Both C-O and Si-O bonds on the plasma treated Si-DLC surface play a significant role in improving the hemocomptatibility.
R. K. Roy et al,Diam. Rel. Mater (2007). Submitted to Acta Biomater. (2008).
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.
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