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ORTHOMANUFACTURE 2018 – Science et Surface – FTIR for degradation mechanisms – C. BRUNON & D. PAVON

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Congrès ORTHOMANUFACTURE – Science et Surface – Conférence du 21/06/2018
Auteurs : C. BRUNON & D. PAVON

Published in: Health & Medicine
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ORTHOMANUFACTURE 2018 – Science et Surface – FTIR for degradation mechanisms – C. BRUNON & D. PAVON

  1. 1. FTIR microscopy contribution for comprehension of Poly-L-Lactic acid (PLLA) degradation mechanisms BAYON Yves1 , ALVES Antoine2 , GROSSIORD Carol3 BRUNON Céline3 , PAVON Delphine3 1 Medtronic, Trévoux, France 2 NAMSA, Chasse/Rhône, France 3 Science et Surface, Ecully, France FTIR microscopy contribution for comprehension of degradation mechanisms in PLA-based implantable medical devices, Leroy, A., Ribeiro, S., Grossiord, C. et al., (J Mater Sci: Mater Med.), 2017
  2. 2. 2 Introduction - PLA and related polymers are widely used materials in medical devices because of their biocompatible and biodegrabable properties. - The history and changes of such polymers after implantation as medical devices (mechanical and/or scaffolding support) should be characterized in situ since they condition their tissue repair functions. - In this study, PLA degradation has been investigated, in particular, in terms of molecular transformation and crystallinity evolution, after implantation in rabbits with correlation to the local tissue reaction. FTIR microscopy contribution for comprehension of degradation mechanisms in PLA-based implantable medical devices, Leroy, A., Ribeiro, S., Grossiord, C. et al., (J Mater Sci: Mater Med.), 2017
  3. 3. 3 Background on Fourier Transform Infrared Spectroscopy (FT-IR) Attenuated Total Reflectance (ATR) µATR (Øanalyzed area: 10 – 100 µm) ATR Imaging (max 500x500 µm²; resolution: 1.6 µm) Specular Imaging (few mm²; resolution: 6 µm) Chemical group analysis Vibration range: 4000 – 400 cm-1 Idenfication From chemical group vibration frequence in the molecule Sensitivity Few % Depth of analysis ≈ (few 10 nm in reflexion mode) FTIR microscopy contribution for comprehension of degradation mechanisms in PLA-based implantable medical devices, Leroy, A., Ribeiro, S., Grossiord, C. et al., (J Mater Sci: Mater Med.), 2017
  4. 4. 4 Literature Data Increase of Crystallinity of PLLA with molecular weight loss #1 Migliaresi, C., et Al (1991). Clinical Materials, 8(1), 111-118. “Crystallinity and viscosimetric molecular weights (Mwv) of four l-lactic acid polymers (PLLA) having different initial molecular weight, i.e. 18 000, 31000, 156000 and 425000, have been determined as functions of the polymer thermal history. Treatments performed in a differential scanning calorimeter (DSC) at various rates showed the different capability of materials to crystallize, due to their different crystallization kinetics and depending on their molecular weight. In the case of cooling from melt, for instance, even at a cooling rate of 0·5 °C/min, only lower molecular weight polymers were able to develop crystallinity.” #2 Zhou, Q., & Xanthos, M. (2008). Polymer degradation and stability, 93(8), 1450-1459. “By focusing on the thermal transitions and crystallization behavior of the PLLA/30B nanocomposite during immersion, Tg was almost relatively constant ( Fig. 8(b)), whereas Tcc shifted to slightly lower temperatures with increasing hydrolysis time. This Tcc change can be related to the lower MW since shorter chains would tend to crystallise at lower temperatures.” … FTIR microscopy contribution for comprehension of degradation mechanisms in PLA-based implantable medical devices, Leroy, A., Ribeiro, S., Grossiord, C. et al., (J Mater Sci: Mater Med.), 2017
  5. 5. 5 Goals with the FTIR – ATR analysis Does the IR spectrum change with PLLA and copolymers of lactic acid hydrolysis? 1/ Investigate the IR spectrum changes occurring after in vitro PLLA degradation 2/ Analyze the degradation topography within PLLA or lactic acid copolymer yarns, after in vivo implantation 3/ Analyze the IR signature of the extracellular matrix interference after implantation of PLLA or lactic acid copolymer yarns FTIR microscopy contribution for comprehension of degradation mechanisms in PLA-based implantable medical devices, Leroy, A., Ribeiro, S., Grossiord, C. et al., (J Mater Sci: Mater Med.), 2017
  6. 6. 6 Materials & Methods In vitro study -Degradation of a PLLA test mesh & control copolymer material TIGR® Matrix Surgical at 90°C, in PBS with regular change of buffer Time : 0h,8h,24h,120h In vivo study -18 New Zealand White male rabbits -8 subcutaneous implants per rabbit: 4 PLLA test meshes & 4 control meshes (control mesh: TIGR® Matrix Surgical (made of copolymers of lactic acic, glycolic acid and trimethylene carbonate - Novus Scientific). -Follow-up: 4, 26 & 52 weeks (n=6 animals per time-period) -Implanted in 3 configurations: original state, partially pre-degraded and highly pre-degraded state FTIR microscopy contribution for comprehension of degradation mechanisms in PLA-based implantable medical devices, Leroy, A., Ribeiro, S., Grossiord, C. et al., (J Mater Sci: Mater Med.), 2017
  7. 7. 7 Materials & Methods Meshes / Tissue explants preparation -Tissue explants embedded in paraffin block & preparation of sections for FTIR (9µm thick section) and histopathology (5µm thick section) FTIR – ATR analysis -FTIR – ATR mode for imaging and mapping made directly on tissue sections over Ge crystal, using Spotlight 400 (Perkin-Elmer) microspectrometer. -Scanned area: 400 x 400 µm² with lateral resolution of 1.6 µm. -Covered spectrum: 720 to 4000 cm-1 with resolution of 8 cm-1. -Correlation with histopathology FTIR microscopy contribution for comprehension of degradation mechanisms in PLA-based implantable medical devices, Leroy, A., Ribeiro, S., Grossiord, C. et al., (J Mater Sci: Mater Med.), 2017
  8. 8. 8 Results: FTIR – ATR analysis of PLLA fibers after in vitro degradation Degradation time at 90°C 0 hr 8 hrs 24 hrs 120 hrs Mn retention (%) 100 60 15 <5 Mass retention (%) 100 >99 >97.5 70 Crystallinity (%)* 48 54 57 73 Legend Increase of the intensity of the 1208 cm-1 & 1130 cm-1 peaks with hydrolysis degree of PLLA PLLA Fibers degradation at 90°C * Deduced from DSC analysis after first heating C-O stretching FTIR microscopy contribution for comprehension of degradation mechanisms in PLA-based implantable medical devices, Leroy, A., Ribeiro, S., Grossiord, C. et al., (J Mater Sci: Mater Med.), 2017
  9. 9. 9 FTIR – ATR analysis of PLLA / Lactic acid copolymer meshes, after implantation Example: PLLA Mesh Slide – Native (T1) – 4 weeks Principal component analysisMicroscopic views of the analyzed field Ratio R1: I (1208 cm-1 ) / I (1180 cm-1 ) Ratio R2: I (1130 cm-1 ) / I (1080 cm-1 ) Histopathology FTIR microscopy contribution for comprehension of degradation mechanisms in PLA-based implantable medical devices, Leroy, A., Ribeiro, S., Grossiord, C. et al., (J Mater Sci: Mater Med.), 2017
  10. 10. 10 FTIR – ATR analysis of PLLA / Lactic acid copolymer meshes, after implantation Degradation evolution of the PLLA mesh (R2 ratio) 4 weeks 26 weeks 52 weeks T1 T2 T3 Histopathology Histopathology Histopathology FTIR microscopy contribution for comprehension of degradation mechanisms in PLA-based implantable medical devices, Leroy, A., Ribeiro, S., Grossiord, C. et al., (J Mater Sci: Mater Med.), 2017
  11. 11. 11 FTIR – ATR analysis of PLLA / Lactic acid copolymer meshes, after implantation Degradation evolution of the PLLA mesh (R2 ratio) – Case of T2 at 52 weeks Principal component analysisMicroscopical views of the analyzed field Fragmentation of PLLA yarns with deposition of extracellular material and cell infiltration in crevices Fragmented PLLA yarn Deposition of proteins in crevices of fragmented PLLA yarns 1646 cm-1 peak (protein; -CONH-) Histopathology FTIR microscopy contribution for comprehension of degradation mechanisms in PLA-based implantable medical devices, Leroy, A., Ribeiro, S., Grossiord, C. et al., (J Mater Sci: Mater Med.), 2017
  12. 12. 12 FTIR – ATR analysis of PLLA / Lactic acid copolymer meshes, after implantation Conclusions 27th European Conference on Biomaterials, Krakow, Poland 30th August – 3rd September 2015 •Setting IR imaging conditions for the monitoring of PLLA aging tracking the degradation extent by intensity ratios at defined IR wave lengths •Imaging of aged PLLA materials with histopathology correlates to better understand the tissue response e.g. hydrolysis, fragmentation, ECM deposit in degraded PLLA •Next steps Semi-quantification of the hydrolysis of lactic acic polymers & copolymers Analysing the changes of the IR signature of the ECM, notably around implanted materials FTIR microscopy contribution for comprehension of degradation mechanisms in PLA-based implantable medical devices, Leroy, A., Ribeiro, S., Grossiord, C. et al., (J Mater Sci: Mater Med.), 2017
  13. 13. Thank you for your attention Partly supported by a grant obtained from Rhone-Alpes region and FUI # 15 (REVAMED collaborative project)(France) 13 FTIR microscopy contribution for comprehension of degradation mechanisms in PLA-based implantable medical devices, Leroy, A., Ribeiro, S., Grossiord, C. et al., (J Mater Sci: Mater Med.), 2017
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