Modélisation statique et dynamique de cations lanthanides ...
Lanthanides as Stabilizing Agents For UHMWPE1. Pennekamp, et al. ORS (2009) • Optimize the...
Transcript of Lanthanides as Stabilizing Agents For UHMWPE1. Pennekamp, et al. ORS (2009) • Optimize the...
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Lanthanides as Stabilizing Agents For UHMWPE
Luis A. Gallardo1 2, Michel Laurent1, Joachim Kunze3 and Markus A. Wimmer1 2
1 Department of Orthopedic Surgery, Rush University Medical Center2 Bioengineering Department, University of Illinois at Chicago, USA3 Department of Analytical Chemistry, Hamburg University of Technology, Germany
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Background• Lanthanoids were tested in vitro as a tracer for wear of
UHMWPE
• UHMWPE was doped with europium and gadolinium stearates
– Tracing capabilities were demonstrated 1
– Doping does not interfere with wear 1
– Abundance of Lanthanides in humans is extremely small 2
– Cyto-compatibility results are promising 2
• Eu(III) stearate doped UHMWPE was tested for oxidative stability and mechanical properties. 3
1. Ngai, et al. Wear (2009)
2. Pennekamp, et al. ORS (2009)
3. Gallardo, et al. MoBT (2009)
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Objectives• Evaluate the oxidative stability of Eu(II)-stearate doped
UHMWPE
– Mechanical properties
– Oxidation index
• Compare Eu(II) doped to conventional and Eu(III) doped UHMWPE
HypothesisThe addition of europium(II) will prevent oxidative degradation of compression molded UHMWPE.
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• Accelerated Aging– ASTM Standard F2003-02
Materials and Methods
γ
• Final Dimensioning
• Gamma Irradiated (35 kGy)
– 70 ̊C, 501 kPa, O2 atmosphere, 14 days
• GUR 1050 UHMWPE powder was doped with Eu(II) and Eu(III) stearates
• Compression molded into slabs, machined to 85x30x20 mm cuboids
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• 200 µm thin films– ASTM STD 2102-06
• FTIR spectra were collected– Line map along axis of SPT cores– From surface to 3 mm depth – 200 µm step intervals
Materials and Methods
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FTIR Micro-Spectroscopy
1200 1300 1400 1500 1600 1700 1800Wavenumber cm-1
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1.2
1.3
1.4
1.5
Abso
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• Normalizing Peak– Methyl Bending– 1400 – 1330 (cm-1)
• Carbonyl Peak– Ketones, esters, carboxylic
acids– 1787 – 1679 (cm-1)
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• Morphology observations were made on each sample – 15x magnification– A visible light polarizer was used to observe the samples– Non-polarized light was used for snapshots
Materials and Methods
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Sample Groups
• Aged and non-aged conditions
• 130 small punch tests were performed in total
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Results
Small Punch Test(Aged Relative to Non Aged)
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* Single measurement curve trends
Load-Deformation Curves
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Note: Error bars represent Standard Error; Bars represent Mean where: n=10
SPT Results
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SPT Results
Note: Error bars represent Standard Error; Bars represent Mean where: n=10
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SPT Results
Note: Error bars represent Standard Error; Bars represent Mean where: n=10
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Results
Surface Oxidation Index (SOI)
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Results
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OI Before Aging
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OI After Aging
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Results
Morphology
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Microscopy Images
Non Doped 750 ppm Eu(III) 7500 ppm Eu(III)50 micron50 micron50 micron
• Europium stearate is accumulated along the grain boundaries (confirmed with FTIR)
• Noticeable only at high concentrations
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FTIR Micro-Spectroscopy
• Carboxylate Peak– Carboxylate Anion Stretching– 1400 – 1330 (cm-1)– Evidence of doping condition,
concentration and location
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1200 1300 1400 1500 1600 1700 1800
Wavenumber [cm-1]
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• Europium stearate shows strong evidence of preserving mechanical properties after aging in both ionic forms.
Conclusions
• FTIR indicates retention of original oxidation indexes in UHMWPE doped with this compound, suggesting stabilization is achieved for this material
– The effect depends upon valence and concentration
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• Yet, counter-intuitively, Eu(III) performed better than Eu(II) on both mechanical and oxidative properties
• There is a drop in initial mechanical properties after doping. It may be due to:
– Solvent residues
– Non optimized compression molding process for this material
Conclusions
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• Gain better understanding of the oxidation reaction dynamics and byproducts
Outlook
1. Pennekamp, et al. ORS (2009)
• Optimize the compression molding process
• Determine the effect of doping on cross-linking
• Capitalize on other properties of Lanthanides that could make them attractive in orthopedics 1:
– Low toxic effects on osteogenic cells
– Anti-proliferate effect on phagocytotic cells
– Anti-inflammatory properties
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Thank you