The Experts below are selected from a list of 318 Experts worldwide ranked by ideXlab platform
Zhiqian Lu - One of the best experts on this subject based on the ideXlab platform.
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microstructure property relationship of l lactide trimethylene carbonate glycolide terpolymers as Cardiovascular Stent material
European Polymer Journal, 2015Co-Authors: Lan Liao, Jianting Dong, Gongxi Wang, Suming Li, Zhiqian LuAbstract:Abstract A series of terpolymers with various compositions were synthesized by ring-opening polymerization of l -lactide (LLA), trimethylene carbonate (TMC) and glycolide (GA), using stannous (II) octoate as initiator. The microstructure–property relationship of the terpolymers was investigated with the aim of evaluating their potential as Cardiovascular Stent material. The chain microstructure of the PLLA–TMC–GA terpolymers was examined by means of both 1H and 13C nuclear magnetic resonance (NMR) analysis, in comparison with corresponding PLLA–TMC copolymers. The results show that the incorporation of GA moiety instead of TMC moiety leads to shorter average LLA block length. Differential scanning calorimetry (DSC) results show a close relationship between the crystallization behavior and the microstructural sequence. The crystallinity of PLLA-based copolymers mainly depends on the average LLA block length. The mechanical and thermal degradation properties are also affected by both the composition and the chain microstructure, which is of major importance for the development of bioresorbable Cardiovascular Stent.
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Microstructure–property relationship of l-lactide/trimethylene carbonate/glycolide terpolymers as Cardiovascular Stent material
European Polymer Journal, 2015Co-Authors: Lan Liao, Jianting Dong, Gongxi Wang, Suming Li, Zhiqian LuAbstract:Abstract A series of terpolymers with various compositions were synthesized by ring-opening polymerization of l -lactide (LLA), trimethylene carbonate (TMC) and glycolide (GA), using stannous (II) octoate as initiator. The microstructure–property relationship of the terpolymers was investigated with the aim of evaluating their potential as Cardiovascular Stent material. The chain microstructure of the PLLA–TMC–GA terpolymers was examined by means of both 1H and 13C nuclear magnetic resonance (NMR) analysis, in comparison with corresponding PLLA–TMC copolymers. The results show that the incorporation of GA moiety instead of TMC moiety leads to shorter average LLA block length. Differential scanning calorimetry (DSC) results show a close relationship between the crystallization behavior and the microstructural sequence. The crystallinity of PLLA-based copolymers mainly depends on the average LLA block length. The mechanical and thermal degradation properties are also affected by both the composition and the chain microstructure, which is of major importance for the development of bioresorbable Cardiovascular Stent.
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a bioresorbable Cardiovascular Stent prepared from l lactide trimethylene carbonate and glycolide terpolymers
Polymer Engineering and Science, 2014Co-Authors: Jianting Dong, Lan Liao, Suming Li, Zhiqian LuAbstract:High molecular weight terpolymers based on L-lactide (LLA), trimethylene carbonate (TMC) and glycolide (GA) are synthesized and characterized with the aim of assessing their potential in the development of bioresorbable Cardiovascular Stents. The effect of the composition on the thermal and mechanical properties of terpolymers is investigated in comparison with the corresponding PLLA-TMC copolymers as well as a PLLA homopolymer. Incorporation of GA units strongly decreases the crystallinity of PLLA-TMC-GA terpolymers due to its more random microstructure as evidenced by C-13 NMR. Meanwhile, the toughness is greatly improved, with only a slight loss of tensile strength. Plasma-treated poly[(L-lactide)-co-glycolide] (PLGA) fibers are used to reinforce the terpolymer matrix. Composite with 8 wt% fibers exhibits much higher tensile strength and modulus. A minitube is fabricated using a single-screw extruder, and a Stent prototype is successfully manufactured from a terpolymer by a CNC engraving machine, thus showing the feasibility of the terpolymers for the development of bioresorbable Cardiovascular Stents. POLYM. ENG. SCI., 54:1418-1426, 2014. (c) 2013 Society of Plastics Engineers
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totally bioresorbable composites prepared from poly l lactide co trimethylene carbonate copolymers and poly l lactide co glycolide fibers as Cardiovascular Stent material
Polymer Engineering and Science, 2012Co-Authors: Jian Yang, Zhiqian Lu, Yong Zhang, Suming LiAbstract:This paper aims to evaluate the potential of totally bioresorbable composites as Cardiovascular Stent material. Copolymers were synthesized by ring-opening polymerization of L-lactide (LLA) and 1,3-trimethylene carbonate (TMC) with LLA-TMC ratios of 3/1, 4/1, and 5/1 and characterized by nuclear magnetic resonance (NMR), gel permeation chromatography (GPC), and differential scanning calorimetry (DSC). Wt. 5% of poly(L-lactide)-co-(glycolide) (PLGA) fibers are used to reinforce PTMC-LLA copolymer matrices to prepare totally bioresorbable composites. Heat treatment under vacuum and oxygen plasma treatment are applied to improve the mechanical performance of the composites in terms of eliminating the imperfections inside, enhancing interfacial affinity, surface roughness, and enriching surface oxidative chemical bonds. After plasma treatment, the viscosity and tensile strength of the fibers decrease, but the surface chemical bonds are enriched and surface roughness is increased. The composites with 15-min plasma-treated fibers and 2 h heat treatment exhibit the highest tensile strength of 46 MPa, i.e., very close to that of PLLA (48 MPa), which is usually used as biodegradable Stent material. Moreover, the tensile modulus of the above composite is 1711 MPa, which is only 34% of PLLA's modulus (4985 MPa). Therefore, novel composites with sufficient tensile strength and better flexibility are obtained as promising Cardiovascular Stent material. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers
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in vitro degradation of poly l lactide co trimethylene carbonate copolymers and a composite with poly l lactide co glycolide fibers as Cardiovascular Stent material
Macromolecular Materials and Engineering, 2012Co-Authors: Zhiqian Lu, Yong Zhang, Suming LiAbstract:TMC/LLA copolymers with several TMC/LLA ratios are synthesized and a composite is obtained by reinforcing with short PLGA fibers. In vitro degradation is studied at 37 °C in pH = 7.4 buffer and compared with a PLLA homopolymer. The degradation of the copolymers appears slower than that of PLLA, showing that TMC units are more resistant to hydrolysis than LLA. Compositional changes indicate a preferential degradation of LLA units as compared to TMC ones. Morphological changes with crystallization of degradation by-products are observed. The composite degrades much faster than the neat copolymer and PLLA because the faster degradation of PLGA fibers speeds up the degradation of the matrix. The composite appears promising for the fabrication of totally bioresorbable Stents.
Diego Mantovani - One of the best experts on this subject based on the ideXlab platform.
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Plasma Surface Modification of 316L Stainless Steel for Cardiovascular Stent Coating
Advanced Materials Research, 2020Co-Authors: Enrico Gallino, Michael Tatoulian, Farzaneh Arefi-khonsari, Diego MantovaniAbstract:Coronary Stents are metallic (316L stainless steel) devices employed during balloon angioplasty to reopen and prevent the re-obstruction of a diseased narrowed area within a coronary artery. To reduce restenosis rate, bare metal Stent coating is a promising solution. The coating can act as an anticorrosive barrier against the aggressive properties of biological environment, improving the long-term safety of the device. The goal of this study is to develop a dry process to isolate metallic surface from the biological environment by depositing a thin plasma polymerized allylamine (CH2=CH-CH2-NH2) film on the metallic surface. Plasma polymerized allylamine films were deposited on flat electropolished 316L stainless steel samples in a low pressure plasma reactor (70 kHz). Chemical composition of the coatings has been analysed as a function of the discharge power and treatment time. Moreover, special attention has been paid on the stability of the coating after immersion during 24 hours in D.I. water. Finally, to mimic Stent expansion conditions, a “small punch test” has been used to investigate the adhesive properties of the coating. Our results demonstrate that is possible to deposit a stable, cohesive and adhesive plasma polymerized allylamine thin film which can be used as a coating for Cardiovascular Stents
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effect of grain sizes on mechanical properties and biodegradation behavior of pure iron for Cardiovascular Stent application
Biomatter, 2016Co-Authors: C S Obayi, R Tolouei, Afghany Mostavan, Carlo Paternoster, Stephane Turgeon, B A Okorie, Daniel Oray Obikwelu, Diego MantovaniAbstract:AbstractPure iron has been demonstrated as a potential candidate for biodegradable metal Stents due to its appropriate biocompatibility, suitable mechanical properties and uniform biodegradation behavior. The competing parameters that control the safety and the performance of BMS include proper strength-ductility combination, biocompatibility along with matching rate of corrosion with healing rate of arteries. Being a micrometre-scale biomedical device, the mentioned variables have been found to be governed by the average grain size of the bulk material. Thermo-mechanical processing techniques of the cold rolling and annealing were used to grain-refine the pure iron. Pure Fe samples were unidirectionally cold rolled and then isochronally annealed at different temperatures with the intention of inducing different ranges of grain size. The effect of thermo-mechanical treatment on mechanical properties and corrosion rates of the samples were investigated, correspondingly. Mechanical properties of pure Fe sam...
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plasma polymerized allylamine films deposited on 316l stainless steel for Cardiovascular Stent coatings
Surface & Coatings Technology, 2010Co-Authors: Enrico Gallino, Michael Tatoulian, Sylvain Massey, Diego MantovaniAbstract:Abstract Coronary Stents are metallic (316L stainless steel) medical devices used during balloon angioplasty to scaffold diseased arteries and prevent their reblockage. To reduce the restenosis rate, bare metal Stent coating is a promising solution. The coating can protect the metallic surface of the Stent from corrosion attack caused by the biological environment. In addition, according to Food and Drug Administration (FDA) the coating properties must be guaranteed even after Stent expansion. The aim of this study was to develop a dry process to coat the metallic surface from the biological environment by depositing an ultra-thin, stable, cohesive and adhesive plasma polymerized allylamine (CH 2 =CH―CH 2 ―NH 2 ) coating with high selectivity towards primary amine groups. Plasma polymerized allylamine (PPAA) coatings were deposited on electropolished 316L stainless steel (316L SS) samples using a low pressure plasma reactor (70 kHz). XPS (X-Ray Photoemission Spectroscopy) and FTIR-ATR (Fourier Transform Infrared-Attenuated Total Reflectance) spectroscopy measurements were used to investigate the chemical composition of the coatings. A chemical derivatization technique was employed in order to quantify the amine retention rate of the deposited films. Morphology of the films was evaluated by FE-SEM (Field Effect-Scanning Electron Microscopy) imaging. Furthermore, special attention was devoted to study the stability of the coating and its adhesion properties after plastic deformation up to 25%. The effect of the power discharge and treatment time on these properties was also investigated. Our results showed that coatings present the required adhesion and cohesion properties to be stable upon deionised (D.I.) water immersion and to resist to a Stent expansion.
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electroformed iron as new biomaterial for degradable Stents development process and structure properties relationship
Acta Biomaterialia, 2010Co-Authors: Maryam Moravej, F Prima, M Fiset, Diego MantovaniAbstract:Abstract An electroforming technique was developed for fabricating iron foils targeted for application as biodegradable Cardiovascular Stent material. The microstructure, mechanical properties and corrosion of electroformed iron (E-Fe) foils were evaluated and compared with those of pure iron made by casting and thermomechanical treatment (CTT-Fe), with 316L stainless steel (316L SS) and with other candidate metallic materials for biodegradable Stents. Electron backscattered diffraction revealed an average grain size of 4 μm for E-Fe, resulting in a high yield (360 MPa) and ultimate tensile strength (423 MPa) being superior to those of other metallic biodegradable Stent materials. Annealing at 550 °C was found to improve the ductility of the E-Fe from 8% to 18%. The corrosion rate of E-Fe in Hanks’ solution, measured by potentiodynamic polarization, was higher than that of CTT-Fe, which had been found to have a slow in vivo degradation. The results showed that E-Fe possesses fine-grain microstructure, suitable mechanical properties and moderate corrosion rate as a degradable Stent material.
Suming Li - One of the best experts on this subject based on the ideXlab platform.
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microstructure property relationship of l lactide trimethylene carbonate glycolide terpolymers as Cardiovascular Stent material
European Polymer Journal, 2015Co-Authors: Lan Liao, Jianting Dong, Gongxi Wang, Suming Li, Zhiqian LuAbstract:Abstract A series of terpolymers with various compositions were synthesized by ring-opening polymerization of l -lactide (LLA), trimethylene carbonate (TMC) and glycolide (GA), using stannous (II) octoate as initiator. The microstructure–property relationship of the terpolymers was investigated with the aim of evaluating their potential as Cardiovascular Stent material. The chain microstructure of the PLLA–TMC–GA terpolymers was examined by means of both 1H and 13C nuclear magnetic resonance (NMR) analysis, in comparison with corresponding PLLA–TMC copolymers. The results show that the incorporation of GA moiety instead of TMC moiety leads to shorter average LLA block length. Differential scanning calorimetry (DSC) results show a close relationship between the crystallization behavior and the microstructural sequence. The crystallinity of PLLA-based copolymers mainly depends on the average LLA block length. The mechanical and thermal degradation properties are also affected by both the composition and the chain microstructure, which is of major importance for the development of bioresorbable Cardiovascular Stent.
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Microstructure–property relationship of l-lactide/trimethylene carbonate/glycolide terpolymers as Cardiovascular Stent material
European Polymer Journal, 2015Co-Authors: Lan Liao, Jianting Dong, Gongxi Wang, Suming Li, Zhiqian LuAbstract:Abstract A series of terpolymers with various compositions were synthesized by ring-opening polymerization of l -lactide (LLA), trimethylene carbonate (TMC) and glycolide (GA), using stannous (II) octoate as initiator. The microstructure–property relationship of the terpolymers was investigated with the aim of evaluating their potential as Cardiovascular Stent material. The chain microstructure of the PLLA–TMC–GA terpolymers was examined by means of both 1H and 13C nuclear magnetic resonance (NMR) analysis, in comparison with corresponding PLLA–TMC copolymers. The results show that the incorporation of GA moiety instead of TMC moiety leads to shorter average LLA block length. Differential scanning calorimetry (DSC) results show a close relationship between the crystallization behavior and the microstructural sequence. The crystallinity of PLLA-based copolymers mainly depends on the average LLA block length. The mechanical and thermal degradation properties are also affected by both the composition and the chain microstructure, which is of major importance for the development of bioresorbable Cardiovascular Stent.
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a bioresorbable Cardiovascular Stent prepared from l lactide trimethylene carbonate and glycolide terpolymers
Polymer Engineering and Science, 2014Co-Authors: Jianting Dong, Lan Liao, Suming Li, Zhiqian LuAbstract:High molecular weight terpolymers based on L-lactide (LLA), trimethylene carbonate (TMC) and glycolide (GA) are synthesized and characterized with the aim of assessing their potential in the development of bioresorbable Cardiovascular Stents. The effect of the composition on the thermal and mechanical properties of terpolymers is investigated in comparison with the corresponding PLLA-TMC copolymers as well as a PLLA homopolymer. Incorporation of GA units strongly decreases the crystallinity of PLLA-TMC-GA terpolymers due to its more random microstructure as evidenced by C-13 NMR. Meanwhile, the toughness is greatly improved, with only a slight loss of tensile strength. Plasma-treated poly[(L-lactide)-co-glycolide] (PLGA) fibers are used to reinforce the terpolymer matrix. Composite with 8 wt% fibers exhibits much higher tensile strength and modulus. A minitube is fabricated using a single-screw extruder, and a Stent prototype is successfully manufactured from a terpolymer by a CNC engraving machine, thus showing the feasibility of the terpolymers for the development of bioresorbable Cardiovascular Stents. POLYM. ENG. SCI., 54:1418-1426, 2014. (c) 2013 Society of Plastics Engineers
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totally bioresorbable composites prepared from poly l lactide co trimethylene carbonate copolymers and poly l lactide co glycolide fibers as Cardiovascular Stent material
Polymer Engineering and Science, 2012Co-Authors: Jian Yang, Zhiqian Lu, Yong Zhang, Suming LiAbstract:This paper aims to evaluate the potential of totally bioresorbable composites as Cardiovascular Stent material. Copolymers were synthesized by ring-opening polymerization of L-lactide (LLA) and 1,3-trimethylene carbonate (TMC) with LLA-TMC ratios of 3/1, 4/1, and 5/1 and characterized by nuclear magnetic resonance (NMR), gel permeation chromatography (GPC), and differential scanning calorimetry (DSC). Wt. 5% of poly(L-lactide)-co-(glycolide) (PLGA) fibers are used to reinforce PTMC-LLA copolymer matrices to prepare totally bioresorbable composites. Heat treatment under vacuum and oxygen plasma treatment are applied to improve the mechanical performance of the composites in terms of eliminating the imperfections inside, enhancing interfacial affinity, surface roughness, and enriching surface oxidative chemical bonds. After plasma treatment, the viscosity and tensile strength of the fibers decrease, but the surface chemical bonds are enriched and surface roughness is increased. The composites with 15-min plasma-treated fibers and 2 h heat treatment exhibit the highest tensile strength of 46 MPa, i.e., very close to that of PLLA (48 MPa), which is usually used as biodegradable Stent material. Moreover, the tensile modulus of the above composite is 1711 MPa, which is only 34% of PLLA's modulus (4985 MPa). Therefore, novel composites with sufficient tensile strength and better flexibility are obtained as promising Cardiovascular Stent material. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers
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in vitro degradation of poly l lactide co trimethylene carbonate copolymers and a composite with poly l lactide co glycolide fibers as Cardiovascular Stent material
Macromolecular Materials and Engineering, 2012Co-Authors: Zhiqian Lu, Yong Zhang, Suming LiAbstract:TMC/LLA copolymers with several TMC/LLA ratios are synthesized and a composite is obtained by reinforcing with short PLGA fibers. In vitro degradation is studied at 37 °C in pH = 7.4 buffer and compared with a PLLA homopolymer. The degradation of the copolymers appears slower than that of PLLA, showing that TMC units are more resistant to hydrolysis than LLA. Compositional changes indicate a preferential degradation of LLA units as compared to TMC ones. Morphological changes with crystallization of degradation by-products are observed. The composite degrades much faster than the neat copolymer and PLLA because the faster degradation of PLGA fibers speeds up the degradation of the matrix. The composite appears promising for the fabrication of totally bioresorbable Stents.
Robin Shandas - One of the best experts on this subject based on the ideXlab platform.
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A survey of surface modification techniques for next-generation shape memory polymer Stent devices
Polymers, 2014Co-Authors: Tina Govindarajan, Robin ShandasAbstract:The search for a single material with ideal surface properties and necessary mechanical properties is on-going, especially with regard to Cardiovascular Stent materials. Since the majority of Stent problems arise from surface issues rather than bulk material deficiencies, surface optimization of a material that already contains the necessary bulk properties is an active area of research. Polymers can be surface-modified using a variety of methods to increase hemocompatibilty by reducing either late-stage restenosis or acute thrombogenicity, or both. These modification methods can be extended to shape memory polymers (SMPs), in an effort to make these materials more surface compatible, based on the application. This review focuses on the role of surface modification of materials, mainly polymers, to improve the hemocompatibility of Stent materials; additional discussion of other materials commonly used in Stents is also provided. Although shape memory polymers are not yet extensively used for Stents, they offer numerous benefits that may make them good candidates for next-generation Stents. Surface modification techniques discussed here include roughening, patterning, chemical modification, and surface modification for biomolecule and drug delivery.
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Unconstrained recovery characterization of shape-memory polymer networks for Cardiovascular applications
Biomaterials, 2007Co-Authors: Christopher Michael Yakacki, Robin Shandas, Craig Lanning, Bryan Rech, Alex Eckstein, Ken GallAbstract:Shape-memory materials have been proposed in biomedical device design due to their ability to facilitate minimally invasive surgery and recover to a predetermined shape in vivo. Use of the shape-memory effect in polymers is proposed for Cardiovascular Stent interventions to reduce the catheter size for delivery and offer highly controlled and tailored deployment at body temperature. Shape-memory polymer networks were synthesized via photopolymerization of tert-butyl acrylate and poly(ethylene glycol) dimethacrylate to provide precise control over the thermomechanical response of the system. The free recovery response of the polymer Stents at body temperature was studied as a function of glass transition temperature (Tg), crosslink density, geometrical perforation, and deformation temperature, all of which can be independently controlled. Room temperature storage of the Stents was shown to be highly dependent on Tg and crosslink density. The pressurized response of the Stents is also demonstrated to depend on crosslink density. This polymer system exhibits a wide range of shape-memory and thermomechanical responses to adapt and meet specific needs of minimally invasive Cardiovascular devices.
Jin Wang - One of the best experts on this subject based on the ideXlab platform.
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surface modification of Cardiovascular Stent material 316l ss with estradiol loaded poly trimethylene carbonate film for better biocompatibility
Polymers, 2017Co-Authors: Jingan Li, Na Li, Kebing Wang, Xin Li, Jin WangAbstract:A delay in the endothelialization process represents a bottleneck in the application of a drug-eluting Stent (DES) during Cardiovascular interventional therapy, which may lead to a high risk of late restenosis. In this study, we used a novel active drug, estradiol, which may contribute to surface endothelialization of a DES, and prepared an estradiol-loaded poly (trimethylene carbonate) film (PTMC-E5) on the surface of the DES material, 316L stainless steel (316L SS), in order to evaluate its function in improving surface endothelialization. All the in vitro and in vivo experiments indicated that the PTMC-E5 film significantly improved surface hemocompatibility and anti-hyperplasia, anti-inflammation and pro-endothelialization properties. This novel drug-delivery system may provide a breakthrough for the surface endothelialization of Cardiovascular DES.
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new strategies for developing Cardiovascular Stent surfaces with novel functions review
Biointerphases, 2014Co-Authors: Pengkai Qi, Si Chen, Jialong Chen, Zhilu Yang, Yajun Weng, Junying Chen, Jin Wang, Manfred F Maitz, Nan HuangAbstract:In this review, the authors summarize the developments in surface modification of Cardiovascular materials especially in author's laboratory. The authors focus on three different strategies to construct multifunctional surfaces including coimmobilization of various biomolecules on Stent surfaces, stem cell based therapy systems, and a single-molecule multipurpose modification strategy in vascular interventional therapy. The roles of various molecules like heparin, gallic acid, various aptamers, and nitric oxide are highlighted in the new strategies for developing Cardiovascular Stent surfaces with novel functions including excellent hemocompatibility, inhibiting smooth muscle cells proliferation, and native endothelium regeneration. The success of these multifunctional surfaces provides the tremendous potential in designing the next generation of vascular Stents.