diamond-like carbon coating for bio-medical implant materials
TRANSCRIPT
Diamond-like Carbon Coating for Bio-medical Implant Materials
Kwang-Ryeol Lee
Future Technology Research DivisionKorea Institute of Science and Technology
[email protected]://diamond.kist.re.kr/DLC
Acknowledgement
• Dr. R. Hauert (EMPA, Switzerland)for valuable discussion and providing me the presentation materials on this issue.
• Prof. Jeong-Ku Kim (SKKU, Korea)for corrosion test in body fluid condition
• Prof. In-Seop Lee (Yonsei Univ., Korea)for tribological test of DLC coated Ti alloys in body fluid
• Prof. Hyeonee Kim (SNU, Korea)for cell attachment and hemocompatbility test
• Prof. R. Wang (UBC, Canada)for mechanical stability test
• Mr. Sejun Park, Mr. Heon-Woong Choi and Ms. Youngjin Lee
• Financial Support from Ministry of Science and Technology of Korea
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 environment5. 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 environment5. Avoid formation of debris
Surface PropertiesSurface Properties
Bioimplant Materials
Required Surface Properties
• Biological Compatibility– Nontoxic, Noncarcinogenic, Noninflammatory
• Chemical Compatibility– Corrosion Resistance
• Mechanical Compatibility– Surface Hardness, Wear Resistance
Diamond-like Carbon :Diamond-like Carbon :as a Strong Candidate Coating as a Strong Candidate Coating
Contents
1. Introduction to DLC
2. Blood Contacting Applications Stents, Heart valves, Flow Accelerators
3. Load Bearing Applications Hip Joints, Knee Joints, Artificial Disk
4. Summary and Technical Issues
Diamond-like Carbon : DLC• Amorphous Solid Carbon Film• Mixture of sp1, sp2 and sp3 Hybridized Bonds• High Content of Hydrogen (20-60%)
t-aC
sp2 H
sp3
DLC
No film
diamond
graphite
Polymer-like
Graphitic
t-aC:H
DLC: A Group of Carbon Mat’l
Properties of Solid Carbon
Property Diamond DLC Graphite
Density (g/cm3) 3.51 1.8 – 3.6 2.26
Atomic Number Density (Mole/cm3)
0.3 0.2 – 0.3 0.2
Hardness (Kgf/mm2) 10000 2000 - 8000 500
Friction Coeff. 0.05 0.03 – 0.2 0.1
Refractive Index 2.42 1.8 – 2.6 2.15 – 1.8
Transparency UV-VIS-IR VIS-IR Opaque
Resistivity (cm) >1016 1010 - 1013 0.2 – 0.4
Applications of DLC
VCR Head Drum
Wrist Pin
Hard Disk & Slider
CD/DVD Mold
Spacer Tool
Form Die
Digital VCR Tape
Razor Blade
Blood Contacting Applications• Heart valves, Stents, Blood pumps etc.
- Surface has to prevent thrombus formation and restenosis
Adsorption of proteins
Increased platelet adhesion
Platelet activation and aggregation
Formation of a thrombusThrombus on a mechanical heart valve
(courtesy of RWTH-Aachen)
albumin/fibrinogen ratio
Steps for Thrombus formation
Protein Adsorption on DLC
a high ratio of albumin/fibrinogen
low number of adhering platelets
low tendency of
thrombus formation 0
0.2
0.4
0.6
0.8
1
1.2
1.4
Ti TiN TiC DLC silicone elastomer
PMMA CN
Alb
um
in /
Fib
rinog
en R
atio
Jones et al.Dion et al.Cui et al.
Albumin/fibrinogen ratio for different surfaces.
Excellent Hemocompatibility
Clotting Time Measurement
On glass
On DLC
Excellent Hemocompatibility
Blood platelets deposited on different surfaces as a function of exposure time.
DLC coated accelerator
PC coated accelerator
DIAMOND AS® Stent
- Reduce thrombus formation
- Prevent Cr, Ni release from 316 L steel
DLC Coated Stents
Potentiodynamic Polarization
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
P
oten
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
DLC Coated Stents
Evolution of Coating Failure
0.00 0.02 0.04 0.06 0.08 0.10 0.120
100
200
300
400
500
Fo
rce
(N)
L/L
(a) (b) (c) (d)
(a)
(b)(c) (d)
CARBOFILM™ made by PVD using a pyrolytic turbostratic carbon target. Probably it is a-C.
Chrome-cobalt alloy cage, coated with CARBOFILM™
Problems: Wear in hinges, Hemocompatibility
DLC Coated Heart Valves etc.
Titanium alloy coated with DLC Products under development by Cardio Carbon Company Ltd.
CarbofilmTM by Sorin Biomedica, Inc.
Polyethylene wear debris is the main factor limiting the lifetime of the implants Aseptic loosening, wear debris initiates inflammatory response, leading to osteoclast cells activation resulting in bone resorption
DLC shows in atmosphere a low wear and also low friction coefficients against most materials
DLC coated femoral heads for low wear ?
DLC slides against its own transfer layer and only DLC is worn at a very low wear rate, whereas the softer partner surface will not be worn
Load Bearing Implants
V. Saikko et al., Biomaterials 22 (2001) 1507
Polyethylene wear debris
DLC Coating on Femoral Ball
RF Power
Cathode
In vitro Wear Test
Pin on Disk
DLC/UHMWPE (literature overview)Hip joint simulator (Lappalainen, Finnland)
Pin on Disk
Lubrication: - air- dest. water - 1wt% NaCl in water
reduction of UHMWPE wear
Hip joint simulator
Lubrication: - diluted calf serum- synovial fluid
no change in UHMWPE wear
To be clinically relevant, tribological investigations on DLC/UHMWPE require:- Adequate tribological setup- Adequate lubricant
In vitro Test
Hip joint simulator
Lubrication: - diluted calf serum- synovial fluid Characterize surface
Texture
single scratches increase the wear rate of UHMWPE by a factor of 30-70
Tribological setup Lubrication Surface quality
phospholipids, adsorbed on the surfaces, strongly influences the tribological behavior and may take part in tribochemical reactions
J. Fisher et al., J. of Engineering in Medicine 209 (1995) 263
S.C. Scholes et al., Phys. Med. Biol. 45 (2000) 372V. Saikko, T. Ahlroos, Wear 207 (1997) 86
Pin-on-Disk setup leads to clinically non relevant results
In vitro Test (only a few papers found)
Lappalainen: Shi: Tiainen:
2003 2003 2001
ta-C/ta-C DLC/stainless steel ta-C/ta-C
hip simulator PoD PoD / hip simulator
bovine serum bovine blood serum NaCl-water
<10-4 mm3/year 50x less than st./st. 100x less than Al2O3/Al2O3
promising result questionable setup questionable lubricantpromising result promising result
Ref: steel/UHMWPE: 20-60 mm3/year (wear particles) steel/steel: 1-5 mm3/year (future allergies)
ceramic/ceramic: 10-2 mm3/year (can only be replaced by ceramic)
R. Lappalainen et al., J. Biomed. Mater. Res. 66B (2003) 410-413 B. Shi et al., Wear 255 (2003) 1015-1021V.-M. Tiainen, Diamond Relat. Mater. 10 (2001) 153-160
DLC/DLC or DLC/metal
Hip Joints: in vivo Test
G. Taeger et al., Mat.-wiss. u. Werkstofftech. 34 (2003) 1094
101 patients DLC/PE101 patients Al2O3/PE
8.5 year’s follow-up50% of DLC/PE failed
DLC/PE
Al2O3/PE
Retrieved DLC-head: Numerous pits revealing the metallic substrate, severe PE wear
Adhesive Wear in Body Fluid
200㎛200㎛
Shoulder-joint, the Ti-alloy ball coated with DLC (carbioceram™)
ankle-joint, AISI Z5 CNMD 21 steelcoated with DLC (carbioceram™)
knee-joints coated with DLC (carbioceram™)
No medical follow-up on these products found
DLC Coated Artificial Joints
Failure Case (Knee Joint)
”Diamond Rota Gliding” DLN/UHMWPE knee-joints have been sold (without the necessary tests and permission) by Implant Design AG in 2001. Dylyn®, DLN (Diamond-like Nanocomposite) produced by Beckaert.
The implanted joints showed increased wear and partial coating delamination and had to be replaced. Additionally, residual coating on the upper side of the implant was held responsible for the inadequate bone ingrowth.
In July 2001 the implantation of this knee joint was forbidden by the Swiss Federal Office of Public Health (SFOPH). www.swissmedic.ch
Summary
• DLC film is not a specific materials but a group of amorhpous carbon materials
• Blood Contacting Applications– Good hemocompatibility– DLC Coated stents, heart valves, blood pumps are
now available in the market.
• Artificial Joints Application– Needs an improved test method to obtain clinically
relevant results. – DLC/DLC or DLC/metal combinations show more
promising results than other combinations.
Technical Issues
• Careful consideration on the DLC film itself is required, because the DLC film is not a specific material.
• Stability of DLC coating in body fluid condition is one of the most critical issues for the biomedical applications.
• Stents– Stability of the coating with respect to the plastic deformation– Interface design would be helpful to increase the reliability.
• Artificial Joints– Characterization of the coating under an adequate test condition
• Does it really reduce the PE debris?• Is it possible to have new design such as DLC/DLC or DLC/metal?
– Stability of the coating during sliding in body fluid condition– Need tight control of the substrate surface
Diamond-like Carbon Coating for Diamond-like Carbon Coating for Bio-medical Implant MaterialsBio-medical Implant Materials
Kwang-Ryeol Lee
Future Technology Research DivisionKorea Institute of Science and Technology
[email protected]://diamond.kist.re.kr/DLC
Cells in contact with DLC
Many in vitro experiments with
different cell types (macrophages,
fibroblasts, human embryo kidney 293
cells, ML-1 cells, osteoblasts etc. )
- good growth rate
- good viability
- no morphological changes
- no cellular damage
- no inflammatory reactions
- no cytotoxicity
DLC may be expected to be
biocompatible in vivo.Cell viability on control and DLC-coated plastic
dished for ML-1 cells [L. Lu, M.W. Jones, R.L.C. Wu, Bio-Med. Mater. Eng. 3 (1993) 223].
Cell Growth Behavior
Thermanox DLC si-DLC0
20000
40000
60000
80000
100000
Cel
l N
um
ber
[/c
m2 ]
Thermanox DLC si-DLC0.00
0.05
0.10
0.15
0.20
AL
P A
ctiv
ity
Proliferation Differentiation
3 days 10 days
(HOS: Human Osteo-sarcoma)
Protein adsorption on Ti-DLC
Adsorption of human plasma proteins on a-C:H/Ti Chromatographic analysis of the proteins. Molecular weight marker is indicated on the left side.
184 kD
115 kD
86.3 kD61.5 kD
50.8 kD
37.6 kD
25.4 kD
Plasma Glas Ti 23 13 7 0
a-C:H, at% Ti
Molecular weight
Tunable protein adsorption between Ti and DLC by the Ti concentration in Ti-DLC.
a-C:Ha-C:Ha-C:H/3% Va-C:H/3% V
a-C:H/7.4% a-C:H/7.4% VV
a-C:H/15% Va-C:H/15% V
after 10 days in vitroafter 10 days in vitro
BMC on V-DLC
Tunable poisoning:
Poisoning of the BMC cells due to vanadium dissolution out of the V-DLC film
300 µm