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Investigating dynamic-mechanical properties of multi-layered materials for biomedical applications

Investigating dynamic-mechanical properties of multi-layered materials for biomedical applications DE GRUYTER Current Directions in Biomedical Engineering 2020;6(3): 20203047 Nicklas Fiedler*, Daniela Arbeiter, Kerstin Schümann, Sabine Illner and Niels Grabow Investigating dynamic-mechanical properties of multi-layered materials for biomedical applications Abstract: The development and advancement of polymeric Medical implant materials technologies that generate implant materials is a frequent focus in current research. The multi-layered structures with a thin top layer onto a base combination of polymeric materials with diverging properties material, for example spray coating, dip coating or provides a wide range of new materials with innovative electrospinning, are frequently used in the field of polymeric characteristics. One technology for combining materials is to material development. In particular, multi-layered structure apply a coated layer onto a base material. could be beneficial, if material properties of the coating are In this work, a hyperelastic, synthetic base material was complementary to those of the base material [6]. Some combined with a rigid biopolymer coating layer. A multi- polycarbonateurethane-co-silicones (PCU-co-Si) generally layered material with combined characteristics of both was show adequate material properties, but still lack in built. In the field of processed polymers, the analysis of biocompatibility or mechanical rigidity, depending on their coating adhesion is not feasible using established methods. previous processing. Solution casted films in combination Therefore, a dynamic-mechanical method was investigated, with a biopolymer coating layer made of chitosan (CS) could which supplements the uniaxial tensile test and provides show improved mechanical properties as well as improved knowledge regarding mechanical resistance of the multi- surface properties for implant-tissue interaction, such as high layered polymer structure. Furthermore, the method gets hydrophilicity. These multi-layered polymeric structures validated by SEM-imaging and evaluation of coating could be useful in various medical applications, such as composition before and after testing under dynamic wound pads, vascular scaffolds and covers for implants or conditions. implantable devices. Established methods for the analysis of coating adhesion Keywords: coating adhesion, multi-layered polymers, are not applicable to examine mechanical properties or biomedical applications, dynamic mechanical testing durability for polymeric coating layers. Due to the high elastic characteristics and morphological structure, e.g. https://doi.org/10.1515/cdbme-2020-3047 porosity, methods like cross-cut and pull-off tests are not expedient [7, 8]. Therefore, a method for dynamic- mechanical testing of multi-layered polymeric materials was 1 Introduction investigated. Especially the examination of delamination, durability and applicability for medical applications, e.g. Polymers are widely used as biomedical implant materials. pulsating stress, or their specific implantation methods was Although their characteristics are highly variable, the intended. combination of two or more polymers can be beneficial for achieving certain properties. Several technologies are described for combining polymers, such as polymer blends or 2 Materials and methods generating multi-layered structures with different technologies [1-5]. 2.1 Sample preparation ______ As base material, a PCU-co-Si film (AdvanSource *Corresponding author: Nicklas Fiedler: Institute for Biomedical Biomaterials Corp., Wilmington, MA, USA) was chosen, Engineering, Rostock University Medical Center, Friedrich- which was subsequently dip-coated with CS (Chitosan highly Barnewitz-Str. 4, 18119 Rostock, Germany, viscous, Sigma-Aldrich GmbH, Steinheim, Germany). e-mail: nicklas.fiedler@uni-rostock.de Daniela Arbeiter, Kerstin Schümann, Sabine Illner and Niels The base material film was manufactured by casting a Grabow: Institute for Biomedical Engineering, Rostock University solution made of 1 g PCU-co-Si granules dissolved in 24 mL Medical Center, Germany Open Access. © 2020 Nicklas Fiedler et al., published by De Gruyter. This work is licensed under the Creative Commons Attribution 4.0 License. Nicklas Fiedler et al., Investigating dynamic-mechanical properties of multi-layered materials for biomedical applications — 2 chloroform. After evaporation of the solvent, the film was average-curve of reference film samples (n=3) and the red washed in methanol and deionized water for 48 hours each. graph the average-curve of CS-coated films (n=3). Figure 1 Subsequently, the samples were annealed at 40 °C for 7 days. shows the stress-strain curves up to ultimate tensile strength The dip-coated CS-layer was applied by dipping the film and material failure. The curve progressions seem to be twice into 0.5% Chitosan dissolved in 0.1 M hydrochloric consistent for uncoated reference samples and coated acid. The resulting CS-coating thickness is 10.1 ± 2.1 µm, samples. Whereas Figure 2 shows the relevant strain range up measured at 20 points for each sample (n=3). to 100% strain, which reveals a slightly higher slope of the All tests were performed comparatively for reference curve in the range below 100% strain for CS-coated samples samples without coating and coated samples. compared to uncoated films. At higher strains, curve progression of coated samples and reference samples are congruent, see Figure 1. 2.2 Uniaxial tensile testing Tensile tests were performed by using a universal testing machine Zwick/Roell Z2.5/TN. (Zwick GmbH & Co. KG, Ulm, Germany). All tests were performed at room temperature (20 °C) and a crosshead speed of 12 mm/min. According to DIN EN ISO 527 standards, all test samples for uniaxial tensile tests have a specimen geometry according to the standard test specimen 1BB [9]. 2.3 Uniaxial dynamic-mechanical testing Figure 1: Stress-strain curves of reference PCU-co-Si films and CS-coated PCU-co-Si films, grey rectangle highlights enlarged For testing the dynamic-mechanical properties and the section, see Figure 2 coating adhesion under tumescent load conditions, the test bench TA ElectroForce BioDynamic 5170 (TA Instruments Inc., New Castle, DE, USA) was used. Therefore, a test protocol with fixed displacement of 2 mm, which corresponds to 15% strain, was applied for 24 hours with a test frequency of 5 Hz. This results in a test with 432,000 load cycles. The tests were conducted in isotonic saline solution at 37 °C and under constant flow conditions. Due to the properties of highly elastic PCU-co-Si films and correspondingly low forces at low elastic deformations, the sample geometry, especially the length-to-width ratio, was adapted to a rectangular 7x20 mm² shape. For further validation of the dynamic-mechanical test results, the morphological structure of the coating was Figure 2: Stress-strain curves from uniaxial tensile tests of investigated with scanning electron microscopy (SEM) using reference samples and CS-coated samples in relevant strain range for subsequent dynamic testing a Quanta FEG 250 (FEI/Thermo Fisher Scientific, USA). The mechanical parameters derived from the results of the uniaxial tensile tests are summarized in Table 1. For quantitative comparison Young’s modulus, ultimate tensile 3 Results and Discussion strength and elongation at break were determined and evaluated. The Young’s modulus was calculated in the range of 0% to 2% elongation to ensure a reasonably accurate 3.1 Uniaxial tensile testing determination. Stress-strain curves from uniaxial tensile tests are shown in Figure 1 and Figure 2. The black graph illustrates the Nicklas Fiedler et al., Investigating dynamic-mechanical properties of multi-layered materials for biomedical applications — 3 Table 1: Mechanical parameters of uncoated and coated The curve progressions of reference and coated samples are PCU-co-Si films derived from uniaxial tensile tests very similar, except the stress-offset that can be observed in coated samples. Hence, the CS-coating on PCU-co-Si films Young’s Tensile Elongation results in a higher stress under dynamic stress conditions. modulus strength at break These findings match the results of tensile tests, where a [MPa] [MPa] [%] slight increase regarding Young’s modulus and particularly PCU-co-Si 2.9 ± 1.3 45.2 ± 4.3 767.4 ± 24.0 higher tensile strength in lower strain ranges was determined (n=3) with coated samples. CS-coated 5.8 ± 1.0 44.8 ± 3.0 760.2 ± 19.7 The morphological structure of the coating was PCU-co-Si investigated with SEM imaging. Figure 4 illustrates a coated (n=3) sample before and after uniaxial cyclic stress conditions. The CS-coating of PCU-co-Si films leads to a duplication regarding Young’s modulus from 2.9 to 5.8 MPa. Tensile strength and elongation at break show less significant changes, a slight decrease is recognizable. An increase in tensile strength and a reduction in elongation at break could have been expected as a result of coating with CS, since coated samples show a higher Young’s modulus. 3.2 Uniaxial dynamic-mechanical Figure 4: Morphological structure of coated PCU-co-Si films testing before (left) and after (right) dynamic-mechanical tests The results of dynamic-mechanical tests for 24 hours (n=3) are illustrated in Figure 3. The curves show a typical progress The surface of untested samples shows some irregularities for maximum sinusoidal tensile stress with a fixed and minor cracks (Figure 4, left). Therefore, the layer displacement. The stress curves of reference films (black) integrity is not optimal before dynamic-mechanical testing. and CS-coated samples (red) decrease with increasing load The right image in Figure 4 indicates the same surface cycles due to relaxation effects. After 1,000 load cycles, the damage following dynamic-mechanical stress that was measured stress decreases slightly until 200,000 load cycles, determined even before mechanical testing. A material for both reference and coated samples. From 200,000 load failure or delamination of the coating layer cannot be cycles onwards the curve progression remains almost determined, since cracks appeared before and after dynamic- constant. Further investigations of films under cyclic load mechanical testing and are unlikely be due to the test itself. conditions should provide supplemental information about Consequently, by combining the results of dynamic- relaxation effects. mechanical examinations and SEM-imaging, the mechanical resistance of CS-coatings on PCU-co-Si films to pulsating stress can only be partially assumed. The occurrence of stress cracks in the CS-coating itself should be prevented by adjusting the process parameters, e.g. dip-time, drying process and layer thickness or by adding plasticizers [10]. 4 Conclusion To summarize, a CS-coating was successfully applied to a PCU-co-Si film base material and a characterization regarding layer adhesion was performed. In addition to the Figure 3: Dynamic-mechanical tests of reference PCU-co-Si tensile test, which characterizes mechanical properties under films and CS-coated PCU-co-Si films quasi-static conditions, a 24-hour dynamic-mechanical test Nicklas Fiedler et al., Investigating dynamic-mechanical properties of multi-layered materials for biomedical applications — 4 was conducted to describe durability of the coating under approval: The conducted research is not related to either cyclic load conditions. Furthermore, it should be taken into human or animal use. account that dynamic-mechanical tests were carried out in isotonic saline solution at 37 °C. References Coating of PCU-co-Si films with CS results in an increased Young’s modulus and higher tensile strength in [1] Pensa NW, Curry AS, Bonvallet PP, Bellis NF, Rettig KM, lower elongation ranges compared to uncoated reference Reddy MS, Eberhardt AW, Bellis SL. 3D printed mesh samples. The general mechanical resistance of the generated reinforcements enhance the mechanical properties of electrospun scaffolds. Biomater Res 23 (2019), multi-layered material was verified for 432,000 load cycles DOI: 10.1186/s40824-019-0171-0 by validating the dynamic-mechanical tests with SEM- [2] D’Amore A, Luketich SK, Hoff R, Ye SH, Wagner WR. imaging. For the valuation of these findings the stress- Blending Polymer Labile Elements at Differing Scales to induced crack formation that was observed before and after Affect Degradation Profiles in Heart Valve Scaffolds. Biomacromolecules 20 (2019), dynamic-mechanical testing, should be taken into account. DOI: 10.1021/acs.biomac.9b00189 These cracks could most likely be prevented by adding [3] Jana S, Lerman A. Behavior of valvular interstitial cells on plasticizers or increasing the layer thickness of CS. trilayered nanofibrous substrate mimicking morphologies of The dynamic-mechanical investigation in this study heart valve leaflet. Acta biomaterialia 85 (2019) represents a first insight into fatigue testing of multi-layered DOI: 10.1016/j.actbio.2018.12.005 [4] Xue J, Wu T, Dai Y, Xia Y. Electrospinning and Electrospun polymer structures. The aim of this investigation was Nanofibers: Methods, Materials, and Applications. Chem. particularly the examination of coating adhesion. The Rev. 119 (2019), DOI: 10.1021/acs.chemrev.8b00593 integrity of the CS-coating itself should be optimized in [5] Jahnavi S, Kumary TV, Bhuvaneshwar GS, Natarajan TS, following studies to prevent crack formation in the coating Verma RS. Engineering of a polymer layered bio-hybrid heart valve scaffold. Mater Sci Eng C Mater Biol Appl. 51 (2015), layer. DOI: 10.1016/j.msec.2015.03.009 [6] Illner S, Arbeiter D, Teske M, Khaimov V, Oschatz S, Senz Acknowledgements V, Schmitz KP, Grabow N, Kohse S. Tissue biomimicry using The authors would like to thank Jonathan Ortelt, Katja Hahn, cross-linked electrospun film fibre composites. Curr. Dir. Babette Hummel and Ingeburg Rühl for their technical Biomed. Eng. (2019), DOI: 10.1515/cdbme-2019-0031 [7] ISO 4624:2016. Paints and varnishes – Pull-off test for assistance and contributions. adhesion [8] ISO 2409:2013. Paints and varnishes – Cross-cut test Author Statement [9] ISO 527-2:2012. Plastics – Determination of tensile Research funding: Partial financial support by the Federal properties – Parts 2: Test conditions for moulding and extrusion plastic Ministry of Education and Research (BMBF) within [10] Suyatma NE, Tighzert L, Copinet A, Coma V. Effects of RESPONSE “Partnership for Innovation in Implant hydrophilic plasticizers on mechanical, thermal, and surface Technology” and by the European Social Fund (ESF) within properties of chitosan films. J Agric Food Chem. 53 (2005), the excellence research program of the state Mecklenburg- DOI: 10.1021/jf048790+ Vorpommern Card-ii-Omics is gratefully acknowledged. Conflict of interest: Authors state no conflict of interest. Informed consent: Informed consent is not applicable. Ethical http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Current Directions in Biomedical Engineering de Gruyter

Investigating dynamic-mechanical properties of multi-layered materials for biomedical applications

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de Gruyter
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© 2020 by Walter de Gruyter Berlin/Boston
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2364-5504
DOI
10.1515/cdbme-2020-3047
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Abstract

DE GRUYTER Current Directions in Biomedical Engineering 2020;6(3): 20203047 Nicklas Fiedler*, Daniela Arbeiter, Kerstin Schümann, Sabine Illner and Niels Grabow Investigating dynamic-mechanical properties of multi-layered materials for biomedical applications Abstract: The development and advancement of polymeric Medical implant materials technologies that generate implant materials is a frequent focus in current research. The multi-layered structures with a thin top layer onto a base combination of polymeric materials with diverging properties material, for example spray coating, dip coating or provides a wide range of new materials with innovative electrospinning, are frequently used in the field of polymeric characteristics. One technology for combining materials is to material development. In particular, multi-layered structure apply a coated layer onto a base material. could be beneficial, if material properties of the coating are In this work, a hyperelastic, synthetic base material was complementary to those of the base material [6]. Some combined with a rigid biopolymer coating layer. A multi- polycarbonateurethane-co-silicones (PCU-co-Si) generally layered material with combined characteristics of both was show adequate material properties, but still lack in built. In the field of processed polymers, the analysis of biocompatibility or mechanical rigidity, depending on their coating adhesion is not feasible using established methods. previous processing. Solution casted films in combination Therefore, a dynamic-mechanical method was investigated, with a biopolymer coating layer made of chitosan (CS) could which supplements the uniaxial tensile test and provides show improved mechanical properties as well as improved knowledge regarding mechanical resistance of the multi- surface properties for implant-tissue interaction, such as high layered polymer structure. Furthermore, the method gets hydrophilicity. These multi-layered polymeric structures validated by SEM-imaging and evaluation of coating could be useful in various medical applications, such as composition before and after testing under dynamic wound pads, vascular scaffolds and covers for implants or conditions. implantable devices. Established methods for the analysis of coating adhesion Keywords: coating adhesion, multi-layered polymers, are not applicable to examine mechanical properties or biomedical applications, dynamic mechanical testing durability for polymeric coating layers. Due to the high elastic characteristics and morphological structure, e.g. https://doi.org/10.1515/cdbme-2020-3047 porosity, methods like cross-cut and pull-off tests are not expedient [7, 8]. Therefore, a method for dynamic- mechanical testing of multi-layered polymeric materials was 1 Introduction investigated. Especially the examination of delamination, durability and applicability for medical applications, e.g. Polymers are widely used as biomedical implant materials. pulsating stress, or their specific implantation methods was Although their characteristics are highly variable, the intended. combination of two or more polymers can be beneficial for achieving certain properties. Several technologies are described for combining polymers, such as polymer blends or 2 Materials and methods generating multi-layered structures with different technologies [1-5]. 2.1 Sample preparation ______ As base material, a PCU-co-Si film (AdvanSource *Corresponding author: Nicklas Fiedler: Institute for Biomedical Biomaterials Corp., Wilmington, MA, USA) was chosen, Engineering, Rostock University Medical Center, Friedrich- which was subsequently dip-coated with CS (Chitosan highly Barnewitz-Str. 4, 18119 Rostock, Germany, viscous, Sigma-Aldrich GmbH, Steinheim, Germany). e-mail: nicklas.fiedler@uni-rostock.de Daniela Arbeiter, Kerstin Schümann, Sabine Illner and Niels The base material film was manufactured by casting a Grabow: Institute for Biomedical Engineering, Rostock University solution made of 1 g PCU-co-Si granules dissolved in 24 mL Medical Center, Germany Open Access. © 2020 Nicklas Fiedler et al., published by De Gruyter. This work is licensed under the Creative Commons Attribution 4.0 License. Nicklas Fiedler et al., Investigating dynamic-mechanical properties of multi-layered materials for biomedical applications — 2 chloroform. After evaporation of the solvent, the film was average-curve of reference film samples (n=3) and the red washed in methanol and deionized water for 48 hours each. graph the average-curve of CS-coated films (n=3). Figure 1 Subsequently, the samples were annealed at 40 °C for 7 days. shows the stress-strain curves up to ultimate tensile strength The dip-coated CS-layer was applied by dipping the film and material failure. The curve progressions seem to be twice into 0.5% Chitosan dissolved in 0.1 M hydrochloric consistent for uncoated reference samples and coated acid. The resulting CS-coating thickness is 10.1 ± 2.1 µm, samples. Whereas Figure 2 shows the relevant strain range up measured at 20 points for each sample (n=3). to 100% strain, which reveals a slightly higher slope of the All tests were performed comparatively for reference curve in the range below 100% strain for CS-coated samples samples without coating and coated samples. compared to uncoated films. At higher strains, curve progression of coated samples and reference samples are congruent, see Figure 1. 2.2 Uniaxial tensile testing Tensile tests were performed by using a universal testing machine Zwick/Roell Z2.5/TN. (Zwick GmbH & Co. KG, Ulm, Germany). All tests were performed at room temperature (20 °C) and a crosshead speed of 12 mm/min. According to DIN EN ISO 527 standards, all test samples for uniaxial tensile tests have a specimen geometry according to the standard test specimen 1BB [9]. 2.3 Uniaxial dynamic-mechanical testing Figure 1: Stress-strain curves of reference PCU-co-Si films and CS-coated PCU-co-Si films, grey rectangle highlights enlarged For testing the dynamic-mechanical properties and the section, see Figure 2 coating adhesion under tumescent load conditions, the test bench TA ElectroForce BioDynamic 5170 (TA Instruments Inc., New Castle, DE, USA) was used. Therefore, a test protocol with fixed displacement of 2 mm, which corresponds to 15% strain, was applied for 24 hours with a test frequency of 5 Hz. This results in a test with 432,000 load cycles. The tests were conducted in isotonic saline solution at 37 °C and under constant flow conditions. Due to the properties of highly elastic PCU-co-Si films and correspondingly low forces at low elastic deformations, the sample geometry, especially the length-to-width ratio, was adapted to a rectangular 7x20 mm² shape. For further validation of the dynamic-mechanical test results, the morphological structure of the coating was Figure 2: Stress-strain curves from uniaxial tensile tests of investigated with scanning electron microscopy (SEM) using reference samples and CS-coated samples in relevant strain range for subsequent dynamic testing a Quanta FEG 250 (FEI/Thermo Fisher Scientific, USA). The mechanical parameters derived from the results of the uniaxial tensile tests are summarized in Table 1. For quantitative comparison Young’s modulus, ultimate tensile 3 Results and Discussion strength and elongation at break were determined and evaluated. The Young’s modulus was calculated in the range of 0% to 2% elongation to ensure a reasonably accurate 3.1 Uniaxial tensile testing determination. Stress-strain curves from uniaxial tensile tests are shown in Figure 1 and Figure 2. The black graph illustrates the Nicklas Fiedler et al., Investigating dynamic-mechanical properties of multi-layered materials for biomedical applications — 3 Table 1: Mechanical parameters of uncoated and coated The curve progressions of reference and coated samples are PCU-co-Si films derived from uniaxial tensile tests very similar, except the stress-offset that can be observed in coated samples. Hence, the CS-coating on PCU-co-Si films Young’s Tensile Elongation results in a higher stress under dynamic stress conditions. modulus strength at break These findings match the results of tensile tests, where a [MPa] [MPa] [%] slight increase regarding Young’s modulus and particularly PCU-co-Si 2.9 ± 1.3 45.2 ± 4.3 767.4 ± 24.0 higher tensile strength in lower strain ranges was determined (n=3) with coated samples. CS-coated 5.8 ± 1.0 44.8 ± 3.0 760.2 ± 19.7 The morphological structure of the coating was PCU-co-Si investigated with SEM imaging. Figure 4 illustrates a coated (n=3) sample before and after uniaxial cyclic stress conditions. The CS-coating of PCU-co-Si films leads to a duplication regarding Young’s modulus from 2.9 to 5.8 MPa. Tensile strength and elongation at break show less significant changes, a slight decrease is recognizable. An increase in tensile strength and a reduction in elongation at break could have been expected as a result of coating with CS, since coated samples show a higher Young’s modulus. 3.2 Uniaxial dynamic-mechanical Figure 4: Morphological structure of coated PCU-co-Si films testing before (left) and after (right) dynamic-mechanical tests The results of dynamic-mechanical tests for 24 hours (n=3) are illustrated in Figure 3. The curves show a typical progress The surface of untested samples shows some irregularities for maximum sinusoidal tensile stress with a fixed and minor cracks (Figure 4, left). Therefore, the layer displacement. The stress curves of reference films (black) integrity is not optimal before dynamic-mechanical testing. and CS-coated samples (red) decrease with increasing load The right image in Figure 4 indicates the same surface cycles due to relaxation effects. After 1,000 load cycles, the damage following dynamic-mechanical stress that was measured stress decreases slightly until 200,000 load cycles, determined even before mechanical testing. A material for both reference and coated samples. From 200,000 load failure or delamination of the coating layer cannot be cycles onwards the curve progression remains almost determined, since cracks appeared before and after dynamic- constant. Further investigations of films under cyclic load mechanical testing and are unlikely be due to the test itself. conditions should provide supplemental information about Consequently, by combining the results of dynamic- relaxation effects. mechanical examinations and SEM-imaging, the mechanical resistance of CS-coatings on PCU-co-Si films to pulsating stress can only be partially assumed. The occurrence of stress cracks in the CS-coating itself should be prevented by adjusting the process parameters, e.g. dip-time, drying process and layer thickness or by adding plasticizers [10]. 4 Conclusion To summarize, a CS-coating was successfully applied to a PCU-co-Si film base material and a characterization regarding layer adhesion was performed. In addition to the Figure 3: Dynamic-mechanical tests of reference PCU-co-Si tensile test, which characterizes mechanical properties under films and CS-coated PCU-co-Si films quasi-static conditions, a 24-hour dynamic-mechanical test Nicklas Fiedler et al., Investigating dynamic-mechanical properties of multi-layered materials for biomedical applications — 4 was conducted to describe durability of the coating under approval: The conducted research is not related to either cyclic load conditions. Furthermore, it should be taken into human or animal use. account that dynamic-mechanical tests were carried out in isotonic saline solution at 37 °C. References Coating of PCU-co-Si films with CS results in an increased Young’s modulus and higher tensile strength in [1] Pensa NW, Curry AS, Bonvallet PP, Bellis NF, Rettig KM, lower elongation ranges compared to uncoated reference Reddy MS, Eberhardt AW, Bellis SL. 3D printed mesh samples. The general mechanical resistance of the generated reinforcements enhance the mechanical properties of electrospun scaffolds. Biomater Res 23 (2019), multi-layered material was verified for 432,000 load cycles DOI: 10.1186/s40824-019-0171-0 by validating the dynamic-mechanical tests with SEM- [2] D’Amore A, Luketich SK, Hoff R, Ye SH, Wagner WR. imaging. For the valuation of these findings the stress- Blending Polymer Labile Elements at Differing Scales to induced crack formation that was observed before and after Affect Degradation Profiles in Heart Valve Scaffolds. Biomacromolecules 20 (2019), dynamic-mechanical testing, should be taken into account. DOI: 10.1021/acs.biomac.9b00189 These cracks could most likely be prevented by adding [3] Jana S, Lerman A. Behavior of valvular interstitial cells on plasticizers or increasing the layer thickness of CS. trilayered nanofibrous substrate mimicking morphologies of The dynamic-mechanical investigation in this study heart valve leaflet. Acta biomaterialia 85 (2019) represents a first insight into fatigue testing of multi-layered DOI: 10.1016/j.actbio.2018.12.005 [4] Xue J, Wu T, Dai Y, Xia Y. Electrospinning and Electrospun polymer structures. The aim of this investigation was Nanofibers: Methods, Materials, and Applications. Chem. particularly the examination of coating adhesion. The Rev. 119 (2019), DOI: 10.1021/acs.chemrev.8b00593 integrity of the CS-coating itself should be optimized in [5] Jahnavi S, Kumary TV, Bhuvaneshwar GS, Natarajan TS, following studies to prevent crack formation in the coating Verma RS. Engineering of a polymer layered bio-hybrid heart valve scaffold. Mater Sci Eng C Mater Biol Appl. 51 (2015), layer. DOI: 10.1016/j.msec.2015.03.009 [6] Illner S, Arbeiter D, Teske M, Khaimov V, Oschatz S, Senz Acknowledgements V, Schmitz KP, Grabow N, Kohse S. Tissue biomimicry using The authors would like to thank Jonathan Ortelt, Katja Hahn, cross-linked electrospun film fibre composites. Curr. Dir. Babette Hummel and Ingeburg Rühl for their technical Biomed. Eng. (2019), DOI: 10.1515/cdbme-2019-0031 [7] ISO 4624:2016. Paints and varnishes – Pull-off test for assistance and contributions. adhesion [8] ISO 2409:2013. Paints and varnishes – Cross-cut test Author Statement [9] ISO 527-2:2012. Plastics – Determination of tensile Research funding: Partial financial support by the Federal properties – Parts 2: Test conditions for moulding and extrusion plastic Ministry of Education and Research (BMBF) within [10] Suyatma NE, Tighzert L, Copinet A, Coma V. Effects of RESPONSE “Partnership for Innovation in Implant hydrophilic plasticizers on mechanical, thermal, and surface Technology” and by the European Social Fund (ESF) within properties of chitosan films. J Agric Food Chem. 53 (2005), the excellence research program of the state Mecklenburg- DOI: 10.1021/jf048790+ Vorpommern Card-ii-Omics is gratefully acknowledged. Conflict of interest: Authors state no conflict of interest. Informed consent: Informed consent is not applicable. Ethical

Journal

Current Directions in Biomedical Engineeringde Gruyter

Published: Sep 1, 2020

Keywords: coating adhesion; multi-layered polymers; biomedical applications; dynamic mechanical testing

There are no references for this article.