The Effect of Static and Dynamic Loading on Degradation of PLLA Stent Fibers

Hayman, Danika; Bergerson, Christie; Miller, Samantha; Moreno, Michael R.; Moore, James E.

doi:10.1115/fmd2013-16149

Cited by 13 publications

(23 citation statements)

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“…It degrades further into carbon dioxide and water in the presence of aerobic bacteria, which are easily assimilated within the body [15,20], thereby making it a suitable candidate for medical devices. Hayman et al [21] measured the effect of PLA hydrolytic degradation on the mechanical properties, observing an increase in degradation upon increasing the applied static or dynamic loading during hydrolysis. Göpferich [22] observed that PLA takes more time for complete degradation on comparison with loss of tensile strength, with steric hindrance being one of the factors for slow degradation.…”

Section: Effect Of Hydrolytic Degradation On the Mechanical Propertiesmentioning

confidence: 99%

Experiment and modelling of the strain-rate-dependent response during in vitro degradation of PLA fibres

et al. 2020

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Polylactic acid (PLA) fibres present, in their pristine state, a strain-rate-dependent behaviour. Their mechanical properties evolve during in vitro biodegradation. Tensile tests of PLA fibres are performed at five different strain rates 0.0001, 0.001, 0.01, 0.05 and 0.1/s and at seven degradation stages, 0, 20, 40, 60, 90, 120 and 150 days in a phosphate buffer solution at constant temperature at 37 °C. The mechanical response is modelled using a modified three-element standard solid model proposed for polymers under finite deformations range. Observations on experimental data lead to the conclusion that the viscous parameters η 1 and η 2 are strain rate dependent, and they vary from 10,762/3202 (N/m s) at the lowest strain rate of 0.0001/s, and 12.2/9.1 (N/m s) at the highest strain rate of 0.1/s for η 1 and η 2 , respectively, thus, depicting the shear-thinning phenomena with the increase in strain rate. Whereas stiffness parameters C 1 and C 2 are degradation dependent, they vary from 21.6/13.7 (N/m) for undegraded PLA fibres and 9.7/5.4 (N/m) for 150 days degraded PLA fibres for C 1 and C 2 , respectively. Decay of stiffness parameters during biodegradation follows an exponential law. The model will be useful to design and develop new fibrous structures for ligament augmentation devices. It could contribute to develop better devices with improved mechanical performance helping those patients in need to repair the ligament tissue.

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Section: Effect Of Hydrolytic Degradation On the Mechanical Propertiesmentioning

confidence: 99%

Experiment and modelling of the strain-rate-dependent response during in vitro degradation of PLA fibres

et al. 2020

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“…A number of models have been presented to predict the mechanical properties of degradable polymers (Hayman et al, 2014;Soares et al, 2010;Vieira et al, 2014;Vieira et al, 2011;Wang et al, 2010). A model was developed by Vieira et al (2014) based on the relationship between fracture strength and molecular weight for thermoplastic polymers to predict the mechanical properties of PLA-PCL fibers during degradation.…”

Section: Introductionmentioning

confidence: 99%

Modelling the degradation and elastic properties of poly(lactic-co-glycolic acid) films and regular open-cell tissue engineering scaffolds

Shirazi

Ronan

Rochev

et al. 2016

Journal of the Mechanical Behavior of Biomedical Materials

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Publication InformationShirazi, RN,Ronan, W,Rochev, Y,McHugh, P (2016) 'Modelling the degradation and elastic properties of poly (lacticco-glycolic AbstractScaffolding plays a critical rule in tissue engineering and an appropriate degradation rate and sufficient mechanical integrity are required during degradation and healing of tissue. This paper presents a computational investigation of the molecular weight degradation and the mechanical performance of poly(lactic-co-glycolic acid) (PLGA) films and tissue engineering scaffolds. A reactiondiffusion model which predicts the degradation behaviour is coupled with an entropy-based mechanical model which relates the Young's modulus and the molecular weight. The model parameters are determined based on experimental data for in-vitro degradation of a PLGA film. Microstructural models of three different scaffold architectures are used to investigate the degradation and mechanical behaviour of each scaffold. Although the architecture of the scaffold does not have a significant influence on the degradation rate, it determines the initial stiffness of the scaffold. It is revealed that the size of the scaffold strut controls the degradation rate and the mechanical collapse. A critical length scale due to competition between diffusion of degradation products and autocatalytic degradation is determined to be in the range 2-100 μm. Below this range, slower homogenous degradation occurs; however, for larger samples monomers are trapped inside the sample and faster autocatalytic degradation occurs.

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“…The effect of static and dynamic loading conditions on degradation of PLLA stent fibres was assessed by Hayman et al (2014) over 15 months to ascertain whether dynamic conditions were required during invitro testing and it was found that it did affect output. In comparison to a static load, dynamic load seemed to accelerate degradation, especially at later time point; however an increase in static load also showed accelerated degradation (Hayman et al 2014). Luo et al (2014) assessed the degradation performance of highmolecular-weight PLLA scaffolds in a mock artery system.…”

Section: Mechanical Performance Of Scaffolds With Degradationmentioning

confidence: 99%

“…Various groups of researchers concentrated on different aspects of simulation of properties and performance of Table 6 Different material model frameworks used for modelling of PLA (Soares et al 2008;Eswaran et al 2011;Söntjens et al 2012;Khan and El-Sayed 2013;Hayman et al 2014 Bobel et al (2015) compiled a comprehensive study of computational bench testing using Abaqus/Standard 6.12 (SIMULIA), to evaluate shortterm mechanical performance of three different stent designs; however, with no consideration for polymeric degradation. A non-linear viscoelastic parallel network model was used to account for material performance; still, there was no account for materials plasticity.…”

Section: Computational and Mathematical Modelling Of Br Scaffoldsmentioning

confidence: 99%

Experimental and computational studies of poly-L-lactic acid for cardiovascular applications: recent progress

Naseem

Zhao

Liu

et al. 2017

Mech Adv Mater Mod Process

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Stents are commonly used in medical procedures to alleviate the symptoms of coronary heart disease, a prevalent modern society disease. These structures are employed to maintain vessel patency and restore blood flow. Traditionally stents are made of metals such as stainless steel or cobalt chromium; however, these scaffolds have known disadvantages. An emergence of transient scaffolds is gaining popularity, with the structure engaged for a required period whilst healing of the diseased arterial wall occurs. Polymers dominate a medical device sector, with incorporation in sutures, scaffolds and screws. Thanks to their good mechanical and biological properties and their ability to degrade naturally. Polylactic acid is an extremely versatile polymer, with its properties easily tailored to applications. Its dominance in the stenting field increases continually, with the first polymer scaffold gaining FDA approval in 2016. Still some challenges with PLLA bioresorbable materials remain, especially with regard to understanding their mechanical response, assessment of its changes with degradation and comparison of their performance with that of metallic drug-eluting stent. Currently, there is still a lack of works on evaluating both the pre-degradation properties and degradation performance of these scaffolds. Additionally, there are no established material models incorporating non-linear viscoelastic behaviour of PLLA and its evolution with in-service degradation. Assessing these features through experimental analysis accompanied by analytical and numerical studies will provide powerful tools for design and optimisation of these structures endorsing their broader use in stenting. This overview assesses the recent studies investigating mechanical and computational performance of poly(l-lactic) acid and its use in stenting applications.

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The Effect of Static and Dynamic Loading on Degradation of PLLA Stent Fibers

Cited by 13 publications

References 0 publications

Experiment and modelling of the strain-rate-dependent response during in vitro degradation of PLA fibres

Experiment and modelling of the strain-rate-dependent response during in vitro degradation of PLA fibres

Modelling the degradation and elastic properties of poly(lactic-co-glycolic acid) films and regular open-cell tissue engineering scaffolds

Experimental and computational studies of poly-L-lactic acid for cardiovascular applications: recent progress

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