A bio-inspired microstructure induced by slow injection moulding of cylindrical block copolymers

Stasiak, Joanna; Brubert, Jacob; Serrani, Marta; Nair, Sridevi; Gaetano, Francesco De; Costantino, Maria Laura; Moggridge, Geoff D.

doi:10.1039/c4sm00884g

Cited by 17 publications

(23 citation statements)

References 35 publications

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“…We have already demonstrated the possibility of orienting the material microstructure in compression and injection molded flat samples [31,40]. Also, we have fabricated compression molded valves that showed acceptable hydrodynamic behavior; although, in these valves, the material microstructure was not optimized.…”

Section: Discussionmentioning

confidence: 99%

“…Further, our group has recently shown the possibility of tuning the microstructure and, consequently, the mechanical properties of this type of polymer by compression and slow injection molding: the investigation of thin molded films of poly(styrene-block-isoprene-block-styrene), a block copolymer characterized by a cylindrical morphology, revealed a layered orientation of the cylinders which depends on the conditions during the manufacturing process (i.e., flow rate and temperature) [31,32]; this layered structure leads to a strong anisotropy of the material, as demonstrated by mechanical tests of material samples. Thus, following a mechanism similar to the native valve where the collagen bundles sustain most of the stress, the optimization of the cylinders' orientation in the valve leaflets could enhance the long-term performance of the PHV, making this class of material an excellent candidate for the development of a new polymeric aortic valve prosthesis [33].…”

Section: Introductionmentioning

confidence: 99%

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A Computational Tool for the Microstructure Optimization of a Polymeric Heart Valve Prosthesis

Serrani

Brubert

Stasiak

et al. 2016

Journal of Biomechanical Engineering

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Styrene-based block copolymers are promising materials for the development of a polymeric heart valve prosthesis (PHV), and the mechanical properties of these polymers can be tuned via the manufacturing process, orienting the cylindrical domains to achieve material anisotropy. The aim of this work is the development of a computational tool for the optimization of the material microstructure in a new PHV intended for aortic valve replacement to enhance the mechanical performance of the device. An iterative procedure was implemented to orient the cylinders along the maximum principal stress direction of the leaflet. A numerical model of the leaflet was developed, and the polymer mechanical behavior was described by a hyperelastic anisotropic constitutive law. A custom routine was implemented to align the cylinders with the maximum Europe PMC Funders Author ManuscriptsEurope PMC Funders Author Manuscripts principal stress direction in the leaflet for each iteration. The study was focused on valve closure, since during this phase the fibrous structure of the leaflets must bear the greatest load. The optimal microstructure obtained by our procedure is characterized by mainly circumferential orientation of the cylinders within the valve leaflet. An increase in the radial strain and a decrease in the circumferential strain due to the microstructure optimization were observed. Also, a decrease in the maximum value of the strain energy density was found in the case of optimized orientation; since the strain energy density is a widely used criterion to predict elastomer's lifetime, this result suggests a possible increase of the device durability if the polymer microstructure is optimized. The present method represents a valuable tool for the design of a new anisotropic PHV, allowing the investigation of different designs, materials, and loading conditions. Keywordspolymeric heart valve; heart valve prosthesis; computational modeling

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

A Computational Tool for the Microstructure Optimization of a Polymeric Heart Valve Prosthesis

Serrani

Brubert

Stasiak

et al. 2016

Journal of Biomechanical Engineering

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“…2 Recently, new emerging material technologies allowed the development of novel polymeric materials with improved and tunable properties: styrenic block copolymer elastomers have a suitable morphology (i.e., stiff cylindrical micro-domains) which may mimic the function and the anisotropic structure of collagen and elastin in the native valve. [3][4][5] The aim of this work was to design, develop and test in vitro PHVs prototypes, according to the outcomes of an ad-hoc implemented finite element model which minimizes the state of stress of the PHV leaflet and optimizes the coaptation area to avoid regurgitation.…”

Section: Introductionmentioning

confidence: 99%

A Newly Developed Tri-Leaflet Polymeric Heart Valve Prosthesis

Gaetano

Bagnoli

Zaffora

et al. 2015

J. Mech. Med. Biol.

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The potential of polymeric heart valves (PHV) prostheses is to combine the hemodynamic performances of biological valves with the durability of mechanical valves. The aim of this work is to design and develop a new tri-leaflet prosthetic heart valve (HV) made from styrenic block copolymers. A computational finite element model was implemented to optimize the thickness of the leaflets, to improve PHV mechanical and hydrodynamic performances. Based on the model outcomes, 8 prototypes of the designed valve were produced and tested in vitro under continuous and pulsatile flow conditions, as prescribed by ISO 5840 Standard. A specially designed pulse duplicator allowed testing the PHVs at different flow rates and frequency conditions. All the PHVs met the requirements specified in ISO 5840 Standard in terms of both regurgitation and effective orifice area (EOA), demonstrating their potential as HV prostheses.

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“…The role of microstructured surfaces in mitigation of platelet adhesion has been demonstrated on poly(lactic- co -glycolic-acid) (PLGA) films, 72 and the generation of microstructures has been implemented via slow injection molding for poly(styrene- block -isoprene- block -styrene) (SIS30), which is structurally similar to SIBS. 73 In addition to these modification, the biocompatibility of xSIBS will be further analyzed for endotoxin load using a limulus amebocyte lysate (LAL) test, as well as cytotoxicity, as per ISO 10993-5 standards. Future studies examining platelet adhesion under flow conditions will statistically analyze the activation state phenotype, as performed by prior studies.…”

Section: Discussionmentioning

confidence: 99%

Physical Characterization and Platelet Interactions under Shear Flows of a Novel Thermoset Polyisobutylene-based Co-polymer

Sheriff

Claiborne

Tran

et al. 2015

ACS Appl. Mater. Interfaces

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Over the years, several polymers have been developed for use in prosthetic heart valves as alternatives to xenografts. However, most of these materials are beset with a variety of issues, including low material strength, biodegradation, high dynamic creep, calcification, and poor hemocompatibility. We studied the mechanical, surface, and flow-mediated thrombogenic response of poly(Styrene-coblock-4-vinylbenzocyclobutene)-polyIsoButylene-poly(Styrene-coblock-4-vinylbenzocylcobutene) (xSIBS), a thermoset version of the thermoplastic elastomeric polyolefin poly(Styrene-block-IsoButylene-block-Styrene) (SIBS), which has been shown to be resistant to in vivo hydrolysis, oxidation, and enzymolysis. Uniaxial tensile testing yielded an ultimate tensile strength of 35 MPa, 24.5 times greater than for SIBS. Surface analysis yielded a mean contact angle of 82.05° and surface roughness of 144 nm, which was greater than for poly(ε-caprolactone) (PCL) and poly(methyl methacrylate) (PMMA). However, the change in platelet activation state, a predictor of thrombogenicity, was not significantly different from PCL and PMMA after fluid exposure to 1 dyne/cm2 and 20 dyne/cm2. In addition, the number of adherent platelets after 10 dyne/cm2 flow exposure was on the same order of magnitude as PCL and PMMA. The mechanical strength and low thrombogenicity of xSIBS therefore suggest it as a viable polymeric substrate for fabrication of prosthetic heart valves, and other cardiovascular devices.

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A bio-inspired microstructure induced by slow injection moulding of cylindrical block copolymers

Abstract: A bi-directional, layered microstructure in cylinder forming block copolymers results from the local balance of shear and extensional flow during slow injection moulding.

Cited by 17 publications

References 35 publications

A Computational Tool for the Microstructure Optimization of a Polymeric Heart Valve Prosthesis

A Computational Tool for the Microstructure Optimization of a Polymeric Heart Valve Prosthesis

A Newly Developed Tri-Leaflet Polymeric Heart Valve Prosthesis

Physical Characterization and Platelet Interactions under Shear Flows of a Novel Thermoset Polyisobutylene-based Co-polymer

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