Acheson, Jonathan

Dunne, Nicholas

Goel, Saurav

Hamilton, Andrew

Lennon, Alex

Ziminska, Monika

English

Queen's University Belfast Research Portal

Nanocomposite-Coated Scaffold Materials with Tailorable Hydrated Mechanical Behaviour

Ulster University's Research Portal

ioengineeringBResearch GroupNanocomposite-Coated Scaffold Materials with Tailorable Hydrated Mechanical BehaviourAcheson, J.1, Ziminska, M.1, Goel, S.2, Lennon, A.1, Dunne, N.3, Hamilton, A.41. School of Mechanical and Aerospace Engineering, Queen’s University Belfast, UK2. Precision Engineering Institute, Cranfield University, UK3. School of Mechanical and Manufacturing Engineering, Dublin City University, Ireland4. Engineering Sciences, University of Southampton, UKioengineeringBResearch Group………………………………………………to tailor mechanical properties of open cell structures• Tissue engineering solutions are an attractive alternative to autograft treatment for bone trauma patientsIntroductionINTRODUCTION MATERIALS AND METHODS RESULTS CONCLUSIONS[Image] Alessandra Giuliani, Synchrotron Radiation and Nanotechnology for Stem Cell Research, Stem Cells in Clinic and Research, 2011• Bone tissue scaffold development has challenges:-• High porosity in conjunction with suitable mechanical properties• Limitation in selection of materialsThin film nanocomposite coatingioengineeringBResearch GroupTunable Structure of Porous MaterialsZiminska et al. ACS Appl Mater Interfaces. 2016;8(34):21968–73.INTRODUCTION MATERIALS AND METHODS RESULTS CONCLUSIONSPorous SubstrateCoated foamPositively charged polyelectrolyteNegatively charged polyelectrolyteNegatively nanoclay plateletsWater sensitive100 µmUn-coated100 µmCoatedCoating has only been tested under ambient conditions. Testing must be done when submerged to examine efficacy under hydrated conditions• Highly porous• Less than desirable mechanical properties• Slightly reduced porosity• Tailored mechanical properties to match surroundingsioengineeringBResearch GroupMaterials • Open cell polyurethane foam• Coated with varying number of quadlayers of:» Poly(ethyleneimine)» Poly(acrylic acid)» Cloisite Na+ nanoclayMethods• Uniaxial compression testing• SEM• Surface profilometry• MicroCT• Mass and elastic modulus in environments of increasing RHHydrated Testing Materials and Methods INTRODUCTION MATERIALS AND METHODS RESULTS CONCLUSIONSioengineeringBResearch GroupCoated Foam Properties when DryINTRODUCTION MATERIALS AND METHODS RESULTS CONCLUSIONS0246810121416182015 QL 30 QL 45 QL 60 QLCoating Thickness (µm)01234560 15 30 45 60Elastic Modulus (E) (MPa)Number of Deposited Quadlayers304050607080901000 5 10 15 20 25 30 35 40 45 50 55 60Coated Foam Mass (mg)Quadlayers Deposited2 mm0.01 MPa4.95 MPaZiminska, et al. ACS Appl Mater Interfaces. 2016;8(34):21968–73.Adapted Ashby-Gibson ModelMechanical properties of open cell materials can be tailoredHow do these coatings act when hydrated?ioengineeringBResearch GroupCoated Foam Properties when WetINTRODUCTION MATERIALS AND METHODS RESULTS CONCLUSIONS0246810120 10 20 30Change in Mass (mg)Time (min)60% RH 85% RHQuadlayersAmbientE ± SD (MPa)HydratedE ± SD (MPa)Hydrated 1 hrE ± SD (MPa)DesiccatedE ± SD (MPa)0 0.08 ± 0.00 0.05 ± 0.00 0.05 ± 0.01 0.10 ± 0.0115 1.31 ± 0.21 0.06 ± 0.01 0.06 ± 0.01 1.08 ± 0.2730 2.78 ± 0.26 0.08 ± 0.01 0.08 ± 0.01 2.54 ± 0.3545 3.19 ± 0.28 0.07 ± 0.01 0.07 ± 0.00 3.52 ± 0.3760 4.90 ± 0.46 0.10 ± 0.01 0.09 ± 0.01 5.17 ± 0.60R² = 0.988390929496981001021041061081100123456Ambient 40 50 60 70 80 90 95Mass (mg)Elastic Modulus (E) (MPa)Relative Humidity (%)Elastic Modulus (MPa)Mass (mg)024681012141618202215 15 30 30 45 45 60 60Thickness (µm)Number of Deposited Quadlayers (n)***** **AmbientHydrated* p-value < 0.05 ** p-value < 0.01ioengineeringBResearch GroupMechanism of Mechanical Property LossINTRODUCTION MATERIALS AND METHODS RESULTS CONCLUSIONSProposed Solution:Hariri, et al. 2012. Macromolecules 45, 9364–9372.ioengineeringBResearch GroupCrosslinking of Coating Design Outline INTRODUCTION MATERIALS AND METHODS RESULTS CONCLUSIONSTwo-level factorial design of experiments (DoE) to investigate crosslinking effectOptimal Crosslinked Coated Foams Characterised:• Hydrated elastic modulus• Coating thickness SEM• Hydrated coated thickness surface profilometry• Mass and elastic modulus in environments of increasing RH• FTIRFactor Parameter Low High Units Factor TypeA Glutaraldehyde Molarity 0 2.5 M ContinuousB Glutaraldehyde Time 30 300 mins ContinuousC Temperature 0 120 °C DiscreteD Temperature Time 60 1500 mins ContinuousE Crosslink Interval 5 30 QL DiscreteTable 5.1 Design of Experiment FactorsOptimise for output:Hydrated elastic modulusioengineeringBResearch GroupDesign of ExperimentsINTRODUCTION MATERIALS AND METHODS RESULTS CONCLUSIONS4050607080901001100.002.004.006.008.0010.0012.00A E AD AE AC D CD BE DE B CE AB C BD BCCumulative Percentage Contributiont-value of |Effect|Factors/InteractionsPositive Effect Negative Effectt-value limit 2.201Factor ParameterA Glutaraldehyde MolarityB Glutaraldehyde TimeC TemperatureD Temperature TimeE Crosslink IntervalFactor/ InteractionPercentage ContributionA 44.58%E 10.50%AD 9.22%AE 8.36%AC 8.14%D 5.14%CD 3.64%BE 2.57%DE 1.99%B 1.24%CE 1.20%AB 1.05%C 1.03%BD 0.86%BC 0.47%0500100015002000-0.5-0.25 0 0.25 0.5 0.75 1 1.25 1.5 1.75 2 2.25 2.5 2.75 3Hydrated Elastic Modulus (kPa)Glutaraldehyde Molarity (M)05001000150020000 5 10 15 20 25 30 35Hydrated Elastic Modulus (kPa)Crosslink Interval (n)Optimal Crosslinking:• Glutaraldehyde Crosslinking at 2.5 M• Glutaraldehyde treatment time of 30 mins• Crosslinking coating every 5 quadlayers depositedioengineeringBResearch GroupOptimal Crosslinked Coated FoamsINTRODUCTION MATERIALS AND METHODS RESULTS CONCLUSIONS0123456Unocated 60 QL 60 QLCrosslinked60 QL 60 QLCrosslinkedElastic Modulus (E) (MPa)051015202560 QL 60 QL 60 QL C 60 QL CThickness (µm)Ambient TestingHydrated Testing  130014001500160017001800Absorbance (au)Wavenumber (cm-1)60 QL60 QL CIncrease in C=N bonds1.97%57%Un-Crosslinked CrosslinkedUn-CrosslinkedCrosslinkedUn-CrosslinkedUn-CrosslinkedCrosslinked CrosslinkedioengineeringBResearch Group• Nanocomposite coatings provide significant improvement in elastic modulus, under ambient conditions• Coating loses almost all of its mechanical properties when hydrated• Effects of water on coating analogous with water acting as a plasticiser as described by others[1,2]• Design of Experiments identified optimised crosslinking parameters:» Glutaraldehyde treatment at 2.5 M for 30 mins, every 5 quadlayers• Crosslinked coated foams retained 57% of their ambient mechanical properties when hydrated compared to 1.97% for uncrosslinked coated foams• Crosslinking of coating allows for tailored hydrated physio-mechanical properties• Coatings can be used to tailor the mechanical and physical structure of bone tissue scaffold materials to match that of surrounding boneConclusionsINTRODUCTION MATERIALS AND METHODS RESULTS CONCLUSIONS[1] Tanchek et al. Langmuir. 2006;22(11):5137–43. [2] Nolte, et al. Macromolecules, 2008:41, 5793–5798.ioengineeringBResearch GroupAcknowledgementsSpecial ThanksDr A HamiltonDr M. ZiminskaProf N DunneDr S GoelDr A Lennonat

Nanocomposite-coated scaffold materials with tailorable hydrated mechanical behaviour

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Nanocomposite-coated scaffold materials with tailorable hydrated mechanical behaviour

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