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.