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Collins CP, Leng J, Fu R, Ding Y, Ameer G, Sun C. Investigation of 3D Printed Bioresorbable Vascular Scaffold Crimping Behavior. ADVANCED MATERIALS TECHNOLOGIES 2024; 9:2301698. [PMID: 39247925 PMCID: PMC11376437 DOI: 10.1002/admt.202301698] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/06/2023] [Indexed: 09/10/2024]
Abstract
The rise in additive manufacturing (AM) offers myriad opportunities for 3D-printed polymeric vascular scaffolds, such as customization and on-the-spot manufacturing, in vivo biodegradation, incorporation of drugs to prevent restenosis, and visibility under X-ray. To maximize these benefits, informed scaffold design is critical. Polymeric bioresorbable vascular scaffolds (BVS) must undergo significant deformation prior to implantation in a diameter-reduction process known as crimping which enables minimally invasive surgery. Understanding the behavior of vascular scaffolds in this step provides twofold benefits: first, it ensures the BVS is able to accommodate stresses occurring during this process to prevent failure, and further, it provides information on the radial strength of the BVS, a key metric to understanding its post-implant performance in the artery. To capitalize on the fast manufacturing speed AM provides, a low time cost solution for understanding scaffold performance during this step is necessary. Through simulation of the BVS crimping process in ABAQUS using experimentally obtained bulk material properties, we have developed a qualitative analysis tool which is capable of accurately comparing relative performance trends of varying BVS designs during crimping in a fraction of the time of experimental testing, thereby assisting in the integration of informed design into the additive manufacturing process.
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Affiliation(s)
- Caralyn P Collins
- Department of Mechanical Engineering, Northwestern University, 2145 Sheridan Rd, Evanston, IL 60208, USA
- Center for Advanced Regenerative Engineering, Northwestern University, 2145 Sheridan Rd, Evanston, IL 60208, USA
| | - Junqing Leng
- Department of Mechanical Engineering, Northwestern University, 2145 Sheridan Rd, Evanston, IL 60208, USA
| | - Rao Fu
- Department of Biomedical Engineering, Worcester Polytechnic Institute, 60 Prescott St, Worcester, MA, 01605, USA
| | - Yonghui Ding
- Department of Biomedical Engineering, Worcester Polytechnic Institute, 60 Prescott St, Worcester, MA, 01605, USA
| | - Guillermo Ameer
- Center for Advanced Regenerative Engineering, Northwestern University, 2145 Sheridan Rd, Evanston, IL 60208, USA
- Department of Biomedical Engineering, Northwestern University, 2145 Sheridan Rd, Evanston, IL 60208, USA
| | - Cheng Sun
- Department of Mechanical Engineering, Northwestern University, 2145 Sheridan Rd, Evanston, IL 60208, USA
- Center for Advanced Regenerative Engineering, Northwestern University, 2145 Sheridan Rd, Evanston, IL 60208, USA
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2
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Abaei AR, Shine CJ, Vaughan TJ, Ronan W. An integrated mechanical degradation model to explore the mechanical response of a bioresorbable polymeric scaffold. J Mech Behav Biomed Mater 2024; 152:106419. [PMID: 38325169 DOI: 10.1016/j.jmbbm.2024.106419] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2023] [Revised: 01/17/2024] [Accepted: 01/23/2024] [Indexed: 02/09/2024]
Abstract
Simulation of bioresorbable medical devices is hindered by the limitations of current material models. Useful simulations require that both the short- and long-term response must be considered; existing models are not physically-based and provide limited insight to guide performance improvements. This study presents an integrated degradation framework which couples a physically-based degradation model, which predicts changes in both crystallinity (Xc) and molecular weight (Mn), with the results of a micromechanical model, which predicts the effective properties of the semicrystalline polymer. This degradation framework is used to simulate the deployment of a bioresorbable PLLA (Poly (L-lactide) stent into a mock vessel and the subsequent mechanical response during degradation under different diffusion boundary conditions representing neointimal growth. A workflow is established in a commercial finite element code that couples both the immediate and long-term responses. Clinically relevant lumen loss is reported and used to compare different responses and the effect of neo-intimal tissue regrowth post-implantation on degradation and on the mechanical response is assessed. In addition, the effects of possible changes in Xc, which could occur during processing and stent deployment, are explored.
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Affiliation(s)
- A R Abaei
- Biomechanics Research Centre (BMEC), Biomedical Engineering, School of Engineering, University of Galway, Ireland
| | - Connor J Shine
- Biomechanics Research Centre (BMEC), Biomedical Engineering, School of Engineering, University of Galway, Ireland
| | - T J Vaughan
- Biomechanics Research Centre (BMEC), Biomedical Engineering, School of Engineering, University of Galway, Ireland
| | - W Ronan
- Biomechanics Research Centre (BMEC), Biomedical Engineering, School of Engineering, University of Galway, Ireland.
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3
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Khatami M, Doniavi A, Abazari AM, Fotouhi M. Enhancing flexibility and strength-to-weight ratio of polymeric stents: A new variable-thickness design approach. J Mech Behav Biomed Mater 2024; 150:106262. [PMID: 38029464 DOI: 10.1016/j.jmbbm.2023.106262] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2023] [Revised: 11/17/2023] [Accepted: 11/20/2023] [Indexed: 12/01/2023]
Abstract
This paper presents a new design strategy to improve the flexibility and strength-to-weight ratio of polymeric stents. The proposed design introduces a variable-thickness (VT) stent that outperforms conventional polymeric stents with constant thickness (CT). While polymeric stents offer benefits like flexibility and bioabsorption, their mechanical strength is lower compared to metal stents. To address this limitation, thicker polymer stents are used, compromising flexibility and clinical performance. Leveraging advancements in 3D printing, a new design approach is introduced in this study and is manufactured by the Liquid Crystal Display (LCD) 3D printing method and PLA resin. The mechanical performance of CT and VT stents is compared using the Finite Element Method (FEM), validated by experimental tests. Results demonstrate that the VT stent offers significant improvements compared to a CT stent in bending stiffness (over 20%), reduced plastic strain distribution of expansion (over 26%), and increased radial strength (over 10%). This research showcases the potential of the VT stent design to enhance clinical outcomes and patient care.
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Affiliation(s)
- Mohamad Khatami
- Department of Mechanical Engineering, Faculty of Engineering, Urmia University, Urmia, Iran.
| | - Ali Doniavi
- Department of Mechanical Engineering, Faculty of Engineering, Urmia University, Urmia, Iran.
| | - Amir Musa Abazari
- Department of Mechanical Engineering, Faculty of Engineering, Urmia University, Urmia, Iran.
| | - Mohammad Fotouhi
- Department of Materials, Mechanics, Management & Design (3MD), Faculty of Civil Engineering and Geosciences, Delft University of Technology, Delft, the Netherlands.
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4
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Balà N, Aranda A, Teixidó P, Molhoek C, Moreno-Jiménez I, Febas G, López-Guimet J, Groothuis A, Edelman ER, Balcells M, Borrós S, Martorell J, Riambau V. In Vivo Efficacy of an Adhesive Bioresorbable Patch to Treat Aortic Dissections. JACC Basic Transl Sci 2024; 9:65-77. [PMID: 38362347 PMCID: PMC10864981 DOI: 10.1016/j.jacbts.2023.08.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/05/2023] [Revised: 06/21/2023] [Accepted: 08/02/2023] [Indexed: 02/17/2024]
Abstract
Endovascular repair of aortic dissection still presents significant limitations. Preserving the mechanical and biological properties set by the aortic microstructure is critical to the success of implantable grafts. In this paper, we present the performance of an adhesive bioresorbable patch designed to cover the entry tear of aortic dissections. We demonstrate the power of using a biomimetic scaffold in a vascular environment.
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Affiliation(s)
- Noemí Balà
- IQS School of Engineering, Universitat Ramon Llull, Barcelona, Spain
- Aortyx SL, Teia, Spain
| | - Alejandro Aranda
- IQS School of Engineering, Universitat Ramon Llull, Barcelona, Spain
- Aortyx SL, Teia, Spain
| | - Pau Teixidó
- IQS School of Engineering, Universitat Ramon Llull, Barcelona, Spain
- Aortyx SL, Teia, Spain
| | - Carlota Molhoek
- IQS School of Engineering, Universitat Ramon Llull, Barcelona, Spain
- Aortyx SL, Teia, Spain
| | | | | | | | - Adam Groothuis
- Institute for Medical Engineering and Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
| | - Elazer Reuven Edelman
- Institute for Medical Engineering and Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
| | - Mercedes Balcells
- IQS School of Engineering, Universitat Ramon Llull, Barcelona, Spain
- Institute for Medical Engineering and Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
| | - Salvador Borrós
- IQS School of Engineering, Universitat Ramon Llull, Barcelona, Spain
- Aortyx SL, Teia, Spain
| | - Jordi Martorell
- IQS School of Engineering, Universitat Ramon Llull, Barcelona, Spain
- Aortyx SL, Teia, Spain
| | - Vicente Riambau
- Aortyx SL, Teia, Spain
- Vascular Surgery Department, Hospital Clínic de Barcelona, Barcelona, Spain
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5
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Gupta K, Meena K. A novel double arrowhead auxetic coronary stent. Comput Biol Med 2023; 166:107525. [PMID: 37778216 DOI: 10.1016/j.compbiomed.2023.107525] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2023] [Revised: 08/17/2023] [Accepted: 09/19/2023] [Indexed: 10/03/2023]
Abstract
A stent implantation is a standard medical procedure for treating coronary artery diseases. Over the years, various different designs have been explored for the stents which come with a range of limitations, including late in-stent restenosis (due to low radial strength), foreshortening, radial recoil, etc. Contrary, stents with auxetic design, characterized by a negative Poisson's ratio, display unique deformation characteristics that result in enhanced mechanical properties in terms of its radial strength, radial recoil, foreshortening, and more. In this study, we have analysed a novel double arrowhead (DA) auxetic stent that aims to overcome the limitations associated with traditional stents, specifically in terms of radial strength, foreshortening, and radial recoil. The parametric analysis was done initially on the DA's unit ring structure to optimize the design by evaluating the effect of three design parameters (angle, amplitude, and width) on the mechanical characteristics (radial strength and radial recoil) using finite element analysis. The width of the strut was found to be the primary determinant of the stent structure's properties. Consequently, the angle and width were found to have the least effect on altering the stent's mechanical properties. After performing the parametric analysis, optimal design factors were selected to design the full-length DA auxetic stent. The mechanical characteristics of the DA auxetic stent were assessed and compared in a case study with the Cypher™ commercial stent. The radial strength of DA auxetic stent was found to be 7.26 N/mm, which is more than double the Cypher™ commercial stent's radial strength. Additionally, the proposed stent possesses reduced radial recoil property and completely eliminates the stent foreshortening issue, which shows the superior mechanical properties of the proposed auxetic stent and its potential as a promising candidate for future stent designs.
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Affiliation(s)
- Khanish Gupta
- Department of Mechanical Engineering, Indian Institute of Technology, Delhi, India.
| | - Kusum Meena
- Department of Mechanical Engineering, Indian Institute of Technology, Delhi, India.
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6
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Dos Santos FJ, Hernandez BA, Santos R, Machado M, Souza M, Capello Sousa EA, Andrade A. Bioabsorbable Polymeric Stent for the Treatment of Coarctation of the Aorta (CoA) in Children: A Methodology to Evaluate the Design and Mechanical Properties of PLA Polymer. MATERIALS (BASEL, SWITZERLAND) 2023; 16:4403. [PMID: 37374585 DOI: 10.3390/ma16124403] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/16/2023] [Revised: 04/26/2023] [Accepted: 05/11/2023] [Indexed: 06/29/2023]
Abstract
This study presents a methodology that combines experimental tests and the finite element method, which is able to analyse the influence of the geometry on the mechanical behaviour of stents made of bioabsorbable polymer PLA (PolyLactic Acid) during their expansion in the treatment of coarctation of the aorta (CoA). Tensile tests with standardized specimen samples were conducted to determine the properties of a 3D-printed PLA. A finite element model of a new stent prototype was generated from CAD files. A rigid cylinder simulating the expansion balloon was also created to simulate the stent opening performance. A tensile test with 3D-printed customized stent specimens was performed to validate the FE stent model. Stent performance was evaluated in terms of elastic return, recoil, and stress levels. The 3D-printed PLA presented an elastic modulus of 1.5 GPa and a yield strength of 30.6 MPa, lower than non-3D-printed PLA. It can also be inferred that crimping had little effect on stent circular recoil performance, as the difference between the two scenarios was on average 1.81%. For an expansion of diameters ranging from 12 mm to 15 mm, as the maximum opening diameter increases, the recoil levels decrease, ranging from 10 to 16.75% within the reported range. These results point out the importance of testing the 3D-printed PLA under the conditions of using it to access its material properties; the results also indicate that the crimping process could be disregarded in simulations to obtain fast results with lower computational cost and that new proposed stent geometry made of PLA might be suitable for use in CoA treatments-the approach that has not been applied before. The next steps will be to simulate the opening of an aorta vessel using this geometry.
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Affiliation(s)
- Flávio José Dos Santos
- Department of Mechanical Engineering, Centre for Simulation in Bioengineering, Biomechanics and Biomaterials, School of Engineering (CS3B), Campus of Bauru, UNESP-São Paulo State University, São Paulo 17033-360, Brazil
| | - Bruno Agostinho Hernandez
- Department of Mechanical Engineering, Centre for Simulation in Bioengineering, Biomechanics and Biomaterials, School of Engineering (CS3B), Campus of Bauru, UNESP-São Paulo State University, São Paulo 17033-360, Brazil
| | - Rosana Santos
- Department of Engineering, PUC-Pontifical Catholic University of São Paulo, São Paulo 05014-901, Brazil
| | - Marcel Machado
- Department of Mechanical Engineering, Centre for Simulation in Bioengineering, Biomechanics and Biomaterials, School of Engineering (CS3B), Campus of Bauru, UNESP-São Paulo State University, São Paulo 17033-360, Brazil
| | - Mateus Souza
- Department of Mechanical Engineering, Centre for Simulation in Bioengineering, Biomechanics and Biomaterials, School of Engineering (CS3B), Campus of Bauru, UNESP-São Paulo State University, São Paulo 17033-360, Brazil
| | - Edson A Capello Sousa
- Department of Mechanical Engineering, Centre for Simulation in Bioengineering, Biomechanics and Biomaterials, School of Engineering (CS3B), Campus of Bauru, UNESP-São Paulo State University, São Paulo 17033-360, Brazil
| | - Aron Andrade
- CEAC-Centre for Engineering in Circulatory Assistance, Dante Pazzanese Institute of Cardiology, São Paulo 04012-909, Brazil
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7
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Hu X, Li J, Yang J, Cheng J, Zhang Y, Lang J, Liu J, Zhao G, Ni Z. Focus on the crucial deformation region to adjust the comprehensive performance of poly (L-lactic acid) stent. Int J Biol Macromol 2023; 230:123417. [PMID: 36709814 DOI: 10.1016/j.ijbiomac.2023.123417] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2022] [Revised: 01/15/2023] [Accepted: 01/21/2023] [Indexed: 01/28/2023]
Abstract
The fully biodegradable polymer stent is considered as the fourth-generation vascular implant with good biocompatibility and long-term therapeutic potential. It has attracted much attention because it overcomes the disadvantage of the permanently implanted metal stent. However, compared with the metal stent, its mechanical properties are slightly inferior, which is an urgent problem. Based on previous studies, fully biodegradable polymer stents are prone to experience cracks and damage in large deformation region during the crimping and expansion process. The large deformation region is mainly located at the ring bend of the stent. We supposed that these damages are the leading causes of weakening the mechanical performance of polymer stents and are mainly affected by the crucial deformation region. For this purpose, this work studies the relationship between different crucial deformation regions and the mechanical performance of the polymer stent. Firstly, the volume of the crucial deformation region is improved by increasing the ring width. Although the radial strength of the stent is enhanced with the increase in ring width, the radial stiffness also increases, and correspondingly, the flexibility of the stent decreases. To obtain acceptable comprehensive mechanical performance, two types of slotting design in critical deformation region were proposed. The proposed slotted stent with a bulge has sufficient radial strength and low radial stiffness, having a good radial support capacity and flexibility. In other words, the proposed stent has improved the radial support without sacrificing flexibility. Overall, different crucial deformation regions cause different degrees of damage to the stent during crimping and expansion, which affects the mechanical properties of the stent. Reasonable structural design of the crucial deformation region is the key to adjust the comprehensive performance of the stent.
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Affiliation(s)
- Xue Hu
- School of Mechanical Engineering, Jiangsu Key Laboratory for Design and Manufacture of Micro-Nano Biomedical Instruments, Southeast University, Nanjing 211189, China
| | - Junjie Li
- School of Mechanical Engineering, Jiangsu Key Laboratory for Design and Manufacture of Micro-Nano Biomedical Instruments, Southeast University, Nanjing 211189, China
| | - Juekuan Yang
- School of Mechanical Engineering, Jiangsu Key Laboratory for Design and Manufacture of Micro-Nano Biomedical Instruments, Southeast University, Nanjing 211189, China
| | - Jie Cheng
- School of Mechanical Engineering, Jiangsu Key Laboratory for Design and Manufacture of Micro-Nano Biomedical Instruments, Southeast University, Nanjing 211189, China
| | - Yi Zhang
- Center of Interventional Radiology & Vascular Surgery, Department of Radiology, Zhongda Hospital, Medical School, Southeast University, Nanjing 210044, China
| | - Ji Lang
- School of Mechanical Engineering, Jiangsu Key Laboratory for Design and Manufacture of Micro-Nano Biomedical Instruments, Southeast University, Nanjing 211189, China
| | - Jinbo Liu
- School of Mechanical Engineering, Jiangsu Key Laboratory for Design and Manufacture of Micro-Nano Biomedical Instruments, Southeast University, Nanjing 211189, China
| | - Gutian Zhao
- School of Mechanical Engineering, Jiangsu Key Laboratory for Design and Manufacture of Micro-Nano Biomedical Instruments, Southeast University, Nanjing 211189, China.
| | - Zhonghua Ni
- School of Mechanical Engineering, Jiangsu Key Laboratory for Design and Manufacture of Micro-Nano Biomedical Instruments, Southeast University, Nanjing 211189, China.
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8
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McGee OM, Geraghty S, Hughes C, Jamshidi P, Kenny DP, Attallah MM, Lally C. An investigation into patient-specific 3D printed titanium stents and the use of etching to overcome Selective Laser Melting design constraints. J Mech Behav Biomed Mater 2022; 134:105388. [DOI: 10.1016/j.jmbbm.2022.105388] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2021] [Revised: 07/05/2022] [Accepted: 07/17/2022] [Indexed: 11/15/2022]
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9
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Loukas VS, Karanasiou GS, Pleouras D, Katsouras CC, Tachos NS, Sakellarios AI, Semertzioglou A, Michalis LK, Fotiadis DI. Investigation of crimping effects on the stent deployment through in silico modeling. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2022; 2022:621-624. [PMID: 36085907 DOI: 10.1109/embc48229.2022.9871622] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Atherosclerosis is one of the most mortal diseases that affects the arterial vessels, due to accumulation of plaque, altering the hemodynamic environment of the artery by preventing the sufficient delivery of blood to other organs. Stents are expandable tubular wires, used as a treatment option. In silico studies have been extensively exploited towards examining the performance of such devices by employing Finite Element Modeling. This study models the crimping stage during stent implantation to examine the effect of inclusion of pre-stress state of the stent. The results show that modeling of the crimping stress state of the stent prior to the deployment results in under-expansion of the stent, due to the indirect inclusion of strain-induced hardening effects. As a result, it is evident that the compressive stent stress configuration is important to be considered in the computational modeling approaches of stent deployment.
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Ong CW, Kumar GP, Zuo K, Koh LB, Charles CJ, Ho P, Leo HL, Cui F. A novel coating method to reduce membrane infolding through pre-crimping of covered stents – Computationaland experimental evaluation. Comput Biol Med 2022; 145:105524. [DOI: 10.1016/j.compbiomed.2022.105524] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2021] [Revised: 04/12/2022] [Accepted: 04/12/2022] [Indexed: 11/24/2022]
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11
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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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12
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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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13
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Antonini L, Poletti G, Mandelli L, Dubini G, Pennati G, Petrini L. Comprehensive computational analysis of the crimping procedure of PLLA BVS: effects of material viscous-plastic and temperature dependent behavior. J Mech Behav Biomed Mater 2021; 123:104713. [PMID: 34365099 DOI: 10.1016/j.jmbbm.2021.104713] [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: 04/26/2021] [Revised: 07/06/2021] [Accepted: 07/08/2021] [Indexed: 10/20/2022]
Abstract
Recently, researchers focused their attention on the use of polymeric bioresorbable vascular scaffolds (BVSs) as alternative to permanent metallic drug-eluting stents (DESs) for the treatment of atherosclerotic coronary arteries. Due to the different mechanical properties, polymeric stents, if compared to DESs, are characterized by larger strut size and specific design. It implies that during the crimping phase, BVSs undergo higher deformation and the packing of the struts, making this process potentially critical for the onset of damage. In this work, a computational study on the crimping procedure of a PLLA stent, inspired by the Absorb GT1 (Abbott Vascular) design, is performed, with the aim of evaluating how different strategies (loading steps, velocities and temperatures) can influence the results in terms of damage risk and final crimped diameter. For these simulations, an elastic-viscous-plastic model was adopted, based on experimental results, obtained from tensile testing of PLLA specimens loaded according to ad hoc experimental protocols. Furthermore, the results of these simulations were compared with those obtained by neglecting strain rate and temperature dependence in the material model (as often done in the literature), showing how this lead to significant differences in the prediction of the crimped diameter and internal stress state.
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Affiliation(s)
- Luca Antonini
- Laboratory of Biological Structure Mechanics, Department of Chemistry, Materials and Chemical Engineering "Giulio Natta", Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133, Milano, Italy.
| | - Gianluca Poletti
- Laboratory of Biological Structure Mechanics, Department of Chemistry, Materials and Chemical Engineering "Giulio Natta", Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133, Milano, Italy.
| | - Lorenzo Mandelli
- Laboratory of Biological Structure Mechanics, Department of Chemistry, Materials and Chemical Engineering "Giulio Natta", Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133, Milano, Italy.
| | - Gabriele Dubini
- Laboratory of Biological Structure Mechanics, Department of Chemistry, Materials and Chemical Engineering "Giulio Natta", Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133, Milano, Italy.
| | - Giancarlo Pennati
- Laboratory of Biological Structure Mechanics, Department of Chemistry, Materials and Chemical Engineering "Giulio Natta", Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133, Milano, Italy.
| | - Lorenza Petrini
- Department of Civil and Environmental Engineering, Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133, Milano, Italy.
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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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15
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Kumar A, Bhatnagar N. Finite element simulation and testing of cobalt-chromium stent: a parametric study on radial strength, recoil, foreshortening, and dogboning. Comput Methods Biomech Biomed Engin 2020; 24:245-259. [PMID: 33021106 DOI: 10.1080/10255842.2020.1822823] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
The effectiveness of cardiovascular stenting procedure depends on the crimping and expansion characteristics of a stent, influenced by its design parameters. In this study, CoCr stents are fabricated, crimped on a tri-folded balloon, and expanded using manual inflation device. Similarly, in the finite element model, a tri-folded balloon is used to expand the stent. The length and diameter are measured to evaluate the radial strength, recoil, foreshortening, and dogboning. The simulation and experimental results match satisfactorily. The validated FE model can be used with confidence to optimize future stent designs, thus reducing the number of testing and product development time.
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Affiliation(s)
- Avinash Kumar
- Department of Mechanical Engineering, Indian Institute of Technology-Delhi, New Delhi, India
| | - Naresh Bhatnagar
- Department of Mechanical Engineering, Indian Institute of Technology-Delhi, New Delhi, India
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16
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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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