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He S, Wei L, Wang G, Pugno NM, Chen Q, Li Z. In Silico Evaluation of In Vivo Degradation Kinetics of Poly(Lactic Acid) Vascular Stent Devices. J Funct Biomater 2024; 15:135. [PMID: 38786646 PMCID: PMC11122488 DOI: 10.3390/jfb15050135] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2024] [Revised: 05/09/2024] [Accepted: 05/11/2024] [Indexed: 05/25/2024] Open
Abstract
Biodegradable vascular stents (BVS) are deemed as great potential alternatives for overcoming the inherent limitations of permanent metallic stents in the treatment of coronary artery diseases. The current study aimed to comprehensively compare the mechanical behaviors of four poly(lactic acid) (PLA) BVS designs with varying geometries via numerical methods and to clarify the optimal BVS selection. Four PLA BVS (i.e., Absorb, DESolve, Igaki-Tamai, and Fantom) were first constructed. A degradation model was refined by simply including the fatigue effect induced by pulsatile blood pressures, and an explicit solver was employed to simulate the crimping and degradation behaviors of the four PLA BVS. The degradation dynamics here were characterized by four indices. The results indicated that the stent designs affected crimping and degradation behaviors. Compared to the other three stents, the DESolve stent had the greatest radial stiffness in the crimping simulation and the best diameter maintenance ability despite its faster degradation; moreover, the stent was considered to perform better according to a pilot scoring system. The current work provides a theoretical method for studying and understanding the degradation dynamics of the PLA BVS, and it could be helpful for the design of next-generation BVS.
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Affiliation(s)
- Shicheng He
- Biomechanics Laboratory, School of Biological Science and Medical Engineering, Southeast University, Nanjing 210096, China
| | - Lingling Wei
- School of Food and Biological Engineering, Hefei University of Technology, Hefei 230601, China
| | - Guixue Wang
- Key Laboratory for Biorheological Science and Technology of Ministry of Education, State and Local Joint Engineering Laboratory for Vascular Implants, Bioengineering College of Chongqing University, Chongqing 400030, China
| | - Nicola M. Pugno
- Laboratory for Bioinspired, Bionic, Nano, Meta Materials and Mechanics, University of Trento, Via Mesiano 77, 38123 Trento, Italy
- School of Engineering and Materials Science, Queen Mary University of London, Mile End Road, London E1 4NS, UK
| | - Qiang Chen
- Biomechanics Laboratory, School of Biological Science and Medical Engineering, Southeast University, Nanjing 210096, China
| | - Zhiyong Li
- Biomechanics Laboratory, School of Biological Science and Medical Engineering, Southeast University, Nanjing 210096, China
- School of Mechanical, Medical and Process Engineering, Queensland University of Technology, Brisbane, QLD 4001, Australia
- Faculty of Sports Science, Ningbo University, Ningbo 315211, China
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Multi-Objective Optimization of Bioresorbable Magnesium Alloy Stent by Kriging Surrogate Model. Cardiovasc Eng Technol 2022; 13:829-839. [PMID: 35414048 DOI: 10.1007/s13239-022-00619-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/14/2021] [Accepted: 03/28/2022] [Indexed: 01/27/2023]
Abstract
PURPOSE The study proposed a multi-objective optimization method based on Kriging surrogate model and finite element analysis to mitigate the redial recoil and foreshortening ratio of bioresorbable magnesium alloy stent, and investigate the impact of strut thickness on stent expansion behavior. METHODS Finite element analysis have been carried out to compare the expansion behavior of stents with various strut thickness. Latin hypercube sampling (LHS) was adopted to generate train sample points in the design space, and the Kriging surrogate model was constructed between strut parameters and stent behavior. The genetic algorithm (GA) was employed to find the optimal solution in the global design space. RESULTS Stents with thinner struts experience lower stress but suffer from severe radial recoil and foreshortening effects. The radial recoil is decreased by 66%, and foreshortening ratio is reduced by 60% for the optimized stent with U-bend width 90.7 [Formula: see text] and link width 77.9 [Formula: see text]. The errors between Kriging surrogate model and finite element simulation are 6% and 9% for the radial recoil and foreshortening ratio. CONCLUSION Stent expansion behavior are highly dependent on design parameters, i.e. thickness, U-bend and link strut width. The purposed Multi-objective optimization approach based on Kriging surrogate model and finite element analysis is efficient in stent design optimization problem.
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Toong DWY, Ng JCK, Cui F, Leo HL, Zhong L, Lian SS, Venkatraman S, Tan LP, Huang YY, Ang HY. Nanoparticles-reinforced poly-l-lactic acid composite materials as bioresorbable scaffold candidates for coronary stents: Insights from mechanical and finite element analysis. J Mech Behav Biomed Mater 2021; 125:104977. [PMID: 34814078 DOI: 10.1016/j.jmbbm.2021.104977] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2021] [Revised: 10/29/2021] [Accepted: 11/12/2021] [Indexed: 12/22/2022]
Abstract
Current generation of bioresorbable coronary scaffolds (BRS) posed thrombogenicity and deployment issues owing to its thick struts and overall profile. To this end, we hypothesize that the use of nanocomposite materials is able to provide improved material properties and sufficient radial strength for the intended application even at reduced strut thickness. The nanocomposite formulations of tantalum dioxide (Ta2O5), L-lactide functionalized (LA)-Ta2O5, hydroxyapatite (HA) and LA-HA with poly-l-lactic acid (PLLA) were evaluated in this study. Results showed that tensile modulus and strength were enhanced with non-functionalized nanofillers up until 15 wt% loading, whereas ductility was compromised. On the other hand, functionalized nanofillers/PLLA exhibited improved nanofiller dispersion which resulted higher tensile modulus, strength, and ductility. Selected nanocomposite formulations were evaluated using finite element analysis (FEA) of a stent with varying strut thickness (80, 100 and 150 μm). FEA data has shown that nanocomposite BRS with thinner struts (80-100 μm) made with 15 wt% LA-Ta2O5/PLLA and 10 wt% LA-HA/PLLA have increased radial strength, stiffness and reduced recoil compared to PLLA BRS at 150 μm. The reduced strut thickness can potentially mitigate issues such as scaffold thrombosis and promote re-endothelialisation of the vessel.
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Affiliation(s)
- Daniel Wee Yee Toong
- School of Materials Science and Engineering, Nanyang Technological University, Nanyang Avenue, 639798, Singapore
| | - Jaryl Chen Koon Ng
- National Heart Research Institute Singapore, National Heart Centre Singapore, 5 Hospital Drive, 169609, Singapore; Department of Biomedical Engineering, National University of Singapore, 4 Engineering Drive 3, 117583, Singapore
| | - Fangsen Cui
- Institute of High Performance Computing, A*STAR, 1 Fusionopolis way, 138632, Singapore
| | - Hwa Liang Leo
- Department of Biomedical Engineering, National University of Singapore, 4 Engineering Drive 3, 117583, Singapore
| | - Liang Zhong
- National Heart Research Institute Singapore, National Heart Centre Singapore, 5 Hospital Drive, 169609, Singapore; Duke-NUS Medical School, 8 College Road, 169857, Singapore
| | - Shaoliang Shawn Lian
- Department of Biomedical Engineering, National University of Singapore, 4 Engineering Drive 3, 117583, Singapore
| | - Subbu Venkatraman
- Department of Material Science Engineering, National University of Singapore, 9 Engineering Drive 1, 117575, Singapore
| | - Lay Poh Tan
- School of Materials Science and Engineering, Nanyang Technological University, Nanyang Avenue, 639798, Singapore
| | - Ying Ying Huang
- School of Materials Science and Engineering, Nanyang Technological University, Nanyang Avenue, 639798, Singapore.
| | - Hui Ying Ang
- National Heart Research Institute Singapore, National Heart Centre Singapore, 5 Hospital Drive, 169609, Singapore; Department of Biomedical Engineering, National University of Singapore, 4 Engineering Drive 3, 117583, Singapore; Duke-NUS Medical School, 8 College Road, 169857, Singapore.
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Conway C, Nezami FR, Rogers C, Groothuis A, Squire JC, Edelman ER. Acute Stent-Induced Endothelial Denudation: Biomechanical Predictors of Vascular Injury. Front Cardiovasc Med 2021; 8:733605. [PMID: 34722666 PMCID: PMC8553954 DOI: 10.3389/fcvm.2021.733605] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2021] [Accepted: 09/15/2021] [Indexed: 01/03/2023] Open
Abstract
Recent concern for local drug delivery and withdrawal of the first Food and Drug Administration-approved bioresorbable scaffold emphasizes the need to optimize the relationships between stent design and drug release with imposed arterial injury and observed pharmacodynamics. In this study, we examine the hypothesis that vascular injury is predictable from stent design and that the expanding force of stent deployment results in increased circumferential stress in the arterial tissue, which may explain acute injury poststent deployment. Using both numerical simulations and ex vivo experiments on three different stent designs (slotted tube, corrugated ring, and delta wing), arterial injury due to device deployment was examined. Furthermore, using numerical simulations, the consequence of changing stent strut radial thickness on arterial wall shear stress and arterial circumferential stress distributions was examined. Regions with predicted arterial circumferential stress exceeding a threshold of 49.5 kPa compared favorably with observed ex vivo endothelial denudation for the three considered stent designs. In addition, increasing strut thickness was predicted to result in more areas of denudation and larger areas exposed to low wall shear stress. We conclude that the acute arterial injury, observed immediately following stent expansion, is caused by high circumferential hoop stresses in the interstrut region, and denuded area profiles are dependent on unit cell geometric features. Such findings when coupled with where drugs move might explain the drug–device interactions.
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Affiliation(s)
- Claire Conway
- Department of Anatomy and Regenerative Medicine, Royal College of Surgeons in Ireland, Dublin, Ireland.,Institute for Medical Engineering and Science, Massachusetts Institute of Technology (MIT), Cambridge, MA, United States.,Trinity Centre for Biomedical Engineering, Trinity College Dublin and Royal College of Surgeons in Ireland, Dublin, Ireland
| | - Farhad R Nezami
- Institute for Medical Engineering and Science, Massachusetts Institute of Technology (MIT), Cambridge, MA, United States.,Thoracic and Cardiac Surgery Division, Department of Surgery, Brigham and Women's Hospital and Harvard Medical School, Boston, MA, United States
| | - Campbell Rogers
- Institute for Medical Engineering and Science, Massachusetts Institute of Technology (MIT), Cambridge, MA, United States.,Cardiovascular Division, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA, United States.,HeartFlow Inc., Redwood City, CA, United States
| | - Adam Groothuis
- Institute for Medical Engineering and Science, Massachusetts Institute of Technology (MIT), Cambridge, MA, United States
| | - James C Squire
- Department of Electrical and Computer Engineering, Virginia Military Institute, Lexington City, KY, United States
| | - Elazer R Edelman
- Institute for Medical Engineering and Science, Massachusetts Institute of Technology (MIT), Cambridge, MA, United States.,Cardiovascular Division, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA, United States
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Computational Analysis of Mechanical Performance for Composite Polymer Biodegradable Stents. MATERIALS 2021; 14:ma14206016. [PMID: 34683608 PMCID: PMC8539075 DOI: 10.3390/ma14206016] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/26/2021] [Revised: 10/03/2021] [Accepted: 10/08/2021] [Indexed: 11/20/2022]
Abstract
Bioresorbable stents (BRS) represent the latest generation of vascular scaffolds used for minimally invasive interventions. They aim to overcome the shortcomings of established bare-metal stents (BMS) and drug-eluting stents (DES). Recent advances in the field of bioprinting offer the possibility of combining biodegradable polymers to produce a composite BRS. Evaluation of the mechanical performance of the novel composite BRS is the focus of this study, based on the idea that they are a promising solution to improve the strength and flexibility performance of single material BRS. Finite element analysis of stent crimping and expansion was performed. Polylactic acid (PLA) and polycaprolactone (PCL) formed a composite stent divided into four layers, resulting in sixteen unique combinations. A comparison of the mechanical performance of the different composite configurations was performed. The resulting stresses, strains, elastic recoil, and foreshortening were evaluated and compared to existing experimental results. Similar behaviour was observed for material configurations that included at least one PLA layer. A pure PCL stent showed significant elastic recoil and less shortening compared to PLA and composite structures. The volumetric ratio of the materials was found to have a more significant effect on recoil and foreshortening than the arrangement of the material layers. Composite BRS offer the possibility of customising the mechanical behaviour of scaffolds. They also have the potential to support the fabrication of personalised or plaque-specific stents.
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Duenas J, Garcia J, Castro F, Munoz J, Sierra-Pallares J. Estimation of degradation velocity of biocompatible damaged stents due to blood flow. IEEE Trans Biomed Eng 2021; 68:3525-3533. [PMID: 33909557 DOI: 10.1109/tbme.2021.3076242] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
OBJECTIVE Bioresorbable materials represent a promising technology for the treatment of coronary disease. Among the different materials employed, magnesium stents display favourable mechanical properties. One of the main uncertainties regarding use is their behaviour when deployed on coronary bifurcations, especially when their retardant coating has been damaged during the implantation process. This paper analyses the temporal evolution of the degradation of a damaged magnesium stent inserted into a coronary bifurcation. METHODS The rate of erosion-corrosion and the effect of the flow configuration on the mass transfer coefficient were estimated on the basis of previous experimental studies and numerical simulations. This coefficient has been employed to reproduce the conditions that can appear in real stent configurations, and computational fluid dynamics simulations were performed. RESULTS The diffusion coefficient for this particular case has been calculated from the mass transfer coefficient and the Sherwood number. The results of the simulation show how the presence of the inner artery wall has a positive effect, preventing a premature degradation of the stent, and how the distal strut is protected by the presence of the proximal struts. CONCLUSIONS This study demonstrates the usefulness of the proposed methodology to evaluate the temporal evolution of the degradation of struts made of magnesium alloys. In addition, this methodology can be applied to a study of different materials and geometric configurations. SIGNIFICANCE The proposed technique can contribute to expanding existing knowledge concerning bioresorbable stent flow-corrosion, thus improving their design and implantation.
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Khalaj Amnieh S, Mashayekhi M, Shahnooshi E, Tavafoghi M, Mosaddegh P. Biodegradable performance of PLA stents affected by geometrical parameters: The risk of fracture and fragment separation. J Biomech 2021; 122:110489. [PMID: 33964575 DOI: 10.1016/j.jbiomech.2021.110489] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2020] [Revised: 03/10/2021] [Accepted: 04/22/2021] [Indexed: 11/19/2022]
Abstract
Biodegradable endovascular stents have been claimed to be reliable candidates for implantation devices used in treating cardiovascular diseases since they reduce the long-term side effects on the human biological system. It is aimed in this study to investigate the effect of geometrical parameters on the degradation behavior of poly (lactic acid) stents in term of strut fracture and fragment separation. In this regard, various structural geometry of the PLA stents was simulated in a stenosed artery using finite element method. For predicting the PLA degradation, a computational model was prepared by which the influence of stents design on their radial strength and fracture was investigated. Using a laboratory-scale designed bioreactor, the PLA fibers degradation was evaluated to calibrate the material parameters and verify the simulation method. Simulation results demonstrated that the geometrical parameters, i.e., number of struts, curves radius and stent cells shape, strongly affect the degradation behavior. The results indicated that the smooth design leads to uniform degradation in the whole stent and decreases the danger of stent fragments separation. It was shown that the maximum degradation rate of the stents with rounded curves was one-third of the models with sharp corners.
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Affiliation(s)
- Sasan Khalaj Amnieh
- Department of Mechanical Engineering, Isfahan University of Technology, Isfahan 84156-83111, Iran
| | - Mohammad Mashayekhi
- Department of Mechanical Engineering, Isfahan University of Technology, Isfahan 84156-83111, Iran
| | - Ehsan Shahnooshi
- Department of Mechanical Engineering, Isfahan University of Technology, Isfahan 84156-83111, Iran
| | - Mehdi Tavafoghi
- Department of Mechanical Engineering, Isfahan University of Technology, Isfahan 84156-83111, Iran
| | - Peiman Mosaddegh
- Department of Mechanical Engineering, Isfahan University of Technology, Isfahan 84156-83111, Iran.
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Singh J, Pandey PM, Kaur T, Singh N. A comparative analysis of solvent cast 3D printed carbonyl iron powder reinforced polycaprolactone polymeric stents for intravascular applications. J Biomed Mater Res B Appl Biomater 2021; 109:1344-1359. [PMID: 33410262 DOI: 10.1002/jbm.b.34795] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2020] [Revised: 12/21/2020] [Accepted: 12/28/2020] [Indexed: 12/13/2022]
Abstract
In the present research, the effectiveness of developed methodology based on solvent cast 3D printing technique was investigated by printing the different geometries of the stents. The carbonyl iron powder (CIP) reinforced polycaprolactone (CIPC) was used to print three pre-existing stent designs such as ABBOTT BVS1.1, PALMAZ-SCHATZ, and ART18Z. The physicochemical behavior was analyzed by X-ray diffraction and scanning electron microscopy. The radial compression test, three-point bending test and stent deployment test were carried out to analyze the mechanical behavior. The degradation behavior of the stents was investigated in static as well as dynamic environment. To investigate the hemocompatible and cytocompatible behaviors of the stents, platelet adhesion test, hemolysis test, protein adsorption, in vitro cell viability test, and live/dead cell viability assay were performed. The results revealed that stents had the adequate mechanical properties to perform the necessary functions in the human coronary. The degradation studies showed slower degradation rate in the dynamic environment in comparison to static environment. in vitro biological analysis indicated that the stents represented excellent resistance to thrombosis, hemocompatible functions as well as cytocompatible nature. The results concluded that PALMAZ-SCHATZ stent represented better mechanical properties, cell viability, blood compatibility, and degradation behavior.
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Affiliation(s)
- Jasvinder Singh
- Department of Mechanical Engineering, Indian Institute of Technology Delhi, New Delhi, India
| | - Pulak Mohan Pandey
- Department of Mechanical Engineering, Indian Institute of Technology Delhi, New Delhi, India
| | - Tejinder Kaur
- Centre for Biomedical Engineering, Indian Institute of Technology Delhi, New Delhi, India
| | - Neetu Singh
- Centre for Biomedical Engineering, Indian Institute of Technology Delhi, New Delhi, India
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Future Balloon-Expandable Stents: High or Low-Strength Materials? Cardiovasc Eng Technol 2019; 11:188-204. [PMID: 31836964 DOI: 10.1007/s13239-019-00450-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/02/2019] [Accepted: 12/07/2019] [Indexed: 10/25/2022]
Abstract
PURPOSE Recent progress in material science allows researchers to use novel materials with enhanced capabilities like optimum biodegradability, higher strength, and flexibility in the design of coronary stents. Considering the wide range of mechanical properties of existing and newfangled materials, finding the influence of variations in mechanical properties of stent materials is critical for developing a practical design. METHODS The sensitivity of stent functional characteristics to variations in its material plastic properties is obtained through FEM modeling. Balloon-expandable coronary stent designs: Absorb BVS, and Xience are examined for artificial and commercial polymeric, and metallic materials, respectively. Standard tests including (1) the crimping process followed by stent implantation in an atherosclerotic artery and (2) the three-point bending test, have been simulated according to ASTM standards. RESULTS In Absorb BVS, materials with higher yield stress than PLLA have similar residual deflection and maximum bending force to PLLA, which is not the case for Xience stent and Co-Cr. Moreover, elevated yield stress significantly reduces stent flexibility only in Xience stent. For both stents, with different degree of influence, an increase in yield or ultimate stress improves stent radial strength and stiffness and reduces arterial stress and plastic strain of stent, which consequently enhances the stent mechanical performance. Contrarily, yield or ultimate stress elevation increases stent recoil which adversely affects stent performance. CONCLUSION Using high-strength materials has a double-edged sword effect on the stent performance and existing uncertainty in the precise estimate of stent mechanical properties adversely affects the reliability of numerical models' predictions.
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