The Experts below are selected from a list of 2022 Experts worldwide ranked by ideXlab platform
Jan Feijen - One of the best experts on this subject based on the ideXlab platform.
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structure formation and hydrogen bonding in all aliphatic Segmented coPolymers with uniform hard segments
Acta Biomaterialia, 2013Co-Authors: Ya I Odarchenko, Pieter J. Dijkstra, Jan Feijen, Niels J Sijbrandi, Ad J Kimenai, Rene Broos, Martin Rosenthal, Dimitri A IvanovAbstract:Abstract Fully aliphatic Segmented Poly(ether ester amide) coPolymers with uniform hard segments prepared by melt Polycondensation of α,ω-hydroxyl end-functionalized Polytetrahydrofuran and short glycine or β-alanine bisester–bisoxalamide units hold promise for biomedical applications. For Polymers with the hard block contents varying from 10% to 27%, differential scanning calorimetry and atomic force microscopy reveal a highly phase-separated morphology, with ribbon-like nanocrystals dispersed in the soft segment matrix. To relate the Polymer properties to the structure of the hard segment, the monomers were prepared and studied by optical and X-ray diffraction measurements. It was shown that the glycine and β-alanine carbonyl ester groups are tilted away from the oxalamide plane, which can affect the degradation rate via hydrolysis of the ester bond.
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synthesis morphology and properties of Segmented Poly ether ester amide s comprising uniform glycine or β alanine extended bisoxalamide hard segments
Polymer, 2012Co-Authors: Niels J Sijbrandi, Jan Feijen, Ad J Kimenai, Edwin P C Mes, Rene Broos, Georg Bar, Martin Rosenthal, Yaroslav Odarchenko, Dimitri A Ivanov, Pieter J. DijkstraAbstract:Segmented Poly(ether ester amide)s comprising glycine or β-alanine extended bisoxalamide hard segments are highly phase separated thermoplastic elastomers with a broad temperature independent rubber plateau. These materials with molecular weights, Mn, exceeding 30 × 103 g mol−1 are conveniently prepared by Polycondensation of preformed bisester–bisoxalamides and commercially available PTHF diols. FT-IR revealed strongly hydrogen bonded and highly ordered bisoxalamide hard segments with degrees of ordering between 73 and 99%. The morphology consists of fiber-like nano-crystals randomly dispersed in the soft Polymer matrix. The micro-structural parameters of the coPolymers were addressed by simultaneous small- and wide-angle X-ray scattering. It is shown that the crystals have strictly identical thickness, which is close to the contour length of the hard segment. The long dimension of the crystals is identified with the direction of the hydrogen bonds. The melting transitions of the hard segments are sharp, with temperatures up to 170 °C. The studied Polymers have an elastic modulus in the range of 139–170 MPa, a stress at break in the range of 19–31 MPa combined with strains at break of higher than 800%. The Segmented coPolymer comprising the β-alanine based bisoxalamide hard segment with a spacer of 6 methylene groups has a melting transition of 141 °C which is higher than the melting transition of its glycine analogue of 119 °C. Likewise, the fracture stress increased from 22 to 31 MPa when the glycine ester group in the hard segment was replaced with β-alanine. The improved thermal and mechanical properties of the latter Polymers is related to the crystal packing of the β-alanine based hard segments in the coPolymer compared to the packing of the hard segments comprising glycine ester groups
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biocompatibility and degradation of aliphatic Segmented Poly ester amide s in vitro and in vivo evaluation
Journal of Biomedical Materials Research Part A, 2006Co-Authors: P.a.m. Lips, I.w. Velthoen, Marja J. A. Van Luyn, Federica Chiellini, Linda A. Brouwer, Piet J. Dijkstra, Jan FeijenAbstract:Aliphatic Segmented Poly(ester amide)s, comprising a crystallizable amide phase and a flexible amorphous ester phase, were investigated for potential use in biomedical applications. By varying the amide content and the type of crystallizable amide segments, the Polymer's thermal and mechanical properties can readily be tuned. Polymers with 25 and 50 mol % of amide content are noncytotoxic and sustain growth of fibroblasts onto Polymer films. The in vitro degradation of these Polymers was followed in PBS (pH 7.4) at 37°C up to 7 months. The Poly(ester amide)s showed the characteristics of bulk degradation with a gradual decrease in molecular weight and almost no mass loss. The in vivo degradation of these Polymers, followed by subcutaneous implantation in rats up to 6 weeks, was slow and similar to the in vitro degradation. The tissue response upon implantation was followed over 6 weeks. A mild foreign-body reaction, characterized by the presence of macrophages, and sporadically a lymphocyte, were observed in the first week of implantation. After 6 weeks the implant site is characterized by fibrous encapsulation with no signs of inflammation. The Poly(ester amide)s tested are biocompatible, but their in vitro as well as in vivo degradation is very slow.
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Gas foaming of Segmented Poly(ester amide) films
Polymer, 2005Co-Authors: P.a.m. Lips, Pieter J. Dijkstra, I.w. Velthoen, Matthias Wessling, Jan FeijenAbstract:Biodegradable Segmented Poly(ester amide)s, based on dimethyl adipate, 1,4-butanediol and N,N?-1,2-ethanediyl-bis[6-hydroxy-hexanamide], with two distinct melting transitions were gas foamed using carbon dioxide (CO2). Polymer films were saturated with CO2 at 50 bar for 6 h after which the pressure was released. The samples were immersed in octane at the desired temperature after which foaming started immediately. Just above the lower melt transition the Polymers retain adequate mechanical properties and dimensional stability, while the chain mobility increased sufficiently to nucleate and expand gas cells during the foaming process. In this way semi-crystalline Poly(ester amide)s can be gas foamed below the flow temperature. Two Poly(ester amide)s with 25 mol% (PEA2,5-25) and 50 mol% (PEA2,5-50) of bisamide segment content were foamed at 70 and 105 °C, respectively. The storage modulus (G?) of both pure Polymers at the onset foaming temperature is 50?60 MPa. Closed-cell foams were obtained with a maximum porosity of not, vert, similar90%. The average pore size of PEA2,5-25 ranges from 77 to 99 ?m. In contrast, the average pore size of PEA2,5-50 is in between 2 and 4 ?m and can be increased to 100 ?m by lowering the CO2 saturation pressure to 20 bar. The porosity of PEA2,5-50 foams using this saturation pressure decreased to 70%
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porous Polymeric structures for tissue engineering prepared by a coagulation compression moulding and salt leaching technique
Biomaterials, 2003Co-Authors: Qingpu Hou, Dirk W Grijpma, Jan FeijenAbstract:A technique for the preparation of porous Polymeric structures involving coagulation, compression moulding and particulate leaching has been developed. The technique combines the advantages of thermal processing methods and particulate leaching. A high molecular weight Polymer solution in an organic solvent containing dispersed water-soluble salt particles is precipitated into an excess of non-solvent. The Polymer–salt composite is then processed by thermal processing methods into devices of varying shapes and sizes, which can subsequently be extracted to give the desired porous structures. The porosities of the scaffolds could be varied between 70% and 95% by adjusting the Polymer to salt ratio and the pore size could be controlled independently by varying the leachable particle size. This versatility provides for the optimisation of scaffolds used in medicine and in tissue engineering. Compared with commonly used porosifying methods such as sintering, compression moulding combined with salt leaching, and freeze-drying, this process allows excellent control over pore size and porosity and yields scaffolds with a much more homogeneous pore morphology. We have prepared porous structures from several relevant Polymers in the biomedical field: Poly( -lactide), Poly(-caprolactone) and 1000PEOT70PBT30, a Segmented Poly(ether ester) based on Polyethylene oxide and Polybutylene terephthalate.
Gustavo A. Abraham - One of the best experts on this subject based on the ideXlab platform.
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Electrospinning of novel biodegradable Poly(ester urethane)s and Poly(ester urethane urea)s for soft tissue-engineering applications
Journal of materials science. Materials in medicine, 2009Co-Authors: Pablo C Caracciolo, Fabian Alejandro Buffa, Vinoy Thomas, Yogesh K. Vohra, Gustavo A. AbrahamAbstract:The development of biomimetic highly-porous scaffolds is essential for successful tissue engineering. Segmented Poly(ester urethane)s and Poly(ester urethane urea)s have been infrequently used for the fabrication of electrospun nanofibrous tissues, which is surprising because these Polymers represent a very large variety of materials with tailored properties. This study reports the preparation of new electrospun elastomeric Polyurethane scaffolds. Two novel Segmented Polyurethanes (SPU), synthesized from Poly(e-caprolactone) diol, 1,6-hexamethylene diisocyanate, and diester-diphenol or diurea-diol chain extenders, were used (Caracciolo et al. in J Mater Sci Mater Med 20:145–155, 2009). The spinnability and the morphology of the electrospun SPU scaffolds were investigated and discussed. The electrospinning parameters such as solution properties (Polymer concentration and solvent) and processing parameters (applied electric field, needle to collector distance and solution flow rate) were optimized to achieve smooth, uniform bead-free fibers with diameter (~700 nm) mimicking the protein fibers of native extracellular matrix (ECM). The obtained elastomeric Polyurethane scaffolds could be appropriate for soft tissue-engineering applications.
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effect of the hard segment chemistry and structure on the thermal and mechanical properties of novel biomedical Segmented Poly esterurethanes
Journal of Materials Science: Materials in Medicine, 2009Co-Authors: Pablo C Caracciolo, Fabian Buffa, Gustavo A. AbrahamAbstract:Two series of biomedical Segmented Polyurethanes (SPU) based on Poly(e-caprolactone) diol (PCL diol), 1,6-hexamethylene diisocyanate (HDI) or l-lysine methyl ester diisocyanate (LDI) and three novel chain extenders, were synthesized and characterized. Chain extenders containing urea groups or an aromatic amino-acid derivative were incorporated in the SPU formulation to strengthen the hard segment interactions through either bidentate hydrogen bonding or π-stacking interactions, respectively. By varying the composition of the hard segment (diisocyanate and chain extender), its structure was varied to investigate the structure-property relationships. The different chemical composition and symmetry of hard segment modulated the phase separation of soft and hard domains, as demonstrated by the thermal behavior. Hard segment association was more enhanced by using a combination of symmetric diisocyanate and urea-diol chain extenders. The hard segment cohesion had an important effect on the observed mechanical behavior. Polyurethanes synthesized using HDI (Series H) were stronger than those obtained using LDI (Series L). The latter SPU exhibited no tendency to undergo cold-drawing and the lowest ultimate properties. Incorporation of the aromatic chain extender produced opposite effects, resulting in Polyurethanes with the highest elongation and tearing energy (Series H) and the lowest strain at break (Series L). Since the synthesized biodegradable SPU possess a range of thermal and mechanical properties, these materials may hold potential for use in soft tissue engineering scaffold applications.
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Segmented Poly esterurethane urea s from novel urea diol chain extenders synthesis characterization and in vitro biological properties
Acta Biomaterialia, 2008Co-Authors: Pablo C Caracciolo, A A A De Queiroz, Olga Z Higa, Fabian Alejandro Buffa, Gustavo A. AbrahamAbstract:This work describes the preparation, physicochemical characterization, mechanical properties and in vitro biological properties of two bioresorbable aliphatic Segmented Poly(esterurethane urea)s (SPEUU) based on Poly(epsilon-caprolactone) diol (PCL diol), 1,6-hexamethylene diisocyanate and two novel urea-diol chain extenders. To strengthen the interactions through hydrogen bonding in the hard segments of SPEUU, novel chain extenders containing urea groups were synthesized and used in the SPEUU formulation. The different chemical structures of the chain extenders modulated the phase separation of soft and hard segments, as demonstrated by the thermal behavior. The hard segment association was enhanced using a diurea-diol chain extender. The biological interactions between the obtained materials and blood were studied by in vitro methods. Research on the protein adsorption, platelet adhesion and thrombus formation is presented. Studies of protein adsorption onto Polymeric surfaces showed that SPEUU adsorbed more albumin than fibrinogen. Studies on platelet adhesion and thrombus formation of SPEUU-coated coverslips indicated the antithrombogenic behavior of these surfaces. The synthesized SPEUU revealed no signs of cytotoxicity to Chinese hamster ovary cells, showing satisfactory cytocompatibility.
Keiichi Takamizawa - One of the best experts on this subject based on the ideXlab platform.
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in vivo tissue engineered small caliber arterial graft prosthesis consisting of autologous tissue biotube
Cell Transplantation, 2004Co-Authors: Yasuhide Nakayama, Hatsue Ishibashiueda, Keiichi TakamizawaAbstract:In this study, vascular-like tubular tissues called biotubes, consisting of autologous tissues, were prepared using in vivo tissue engineering. Their mechanical properties were evaluated for application as a small-caliber artificial vascular prosthesis. The biotubes were prepared by embedding six kinds of Polymeric rods [Poly(ethylene) (PE), Poly(fluoroacetate) (PFA), Poly(methyl methacrylate) (PMMA), Segmented Poly(urethane) (PU), Poly(vinyl chloride) (PVC), and silicone (Si)] as a mold in six subcutaneous pouches in the dorsal skin of New Zealand White rabbits. For rods apart from PFA, biotubes were constructed after 1 month of implantation by encapsulation around the Polymeric implants. The wall thickness of the biotubes ranged from about 50 to 200 μm depending on the implant material and were in the order PFA < PVC < PMMA < PU < PE. As for PE, PMMA, and PVC, the thickness increased after 3 months of implantation and ranged from 1.5-to 2-fold. None of the biotubes were ruptured when a hydrostatic press...
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in vivo tissue engineered small caliber arterial graft prosthesis consisting of autologous tissue biotube
Cell Transplantation, 2004Co-Authors: Yasuhide Nakayama, Hatsue Ishibashiueda, Keiichi TakamizawaAbstract:In this study, vascular-like tubular tissues called biotubes, consisting of autologous tissues, were prepared using in vivo tissue engineering. Their mechanical properties were evaluated for application as a small-caliber artificial vascular prosthesis. The biotubes were prepared by embedding six kinds of Polymeric rods [Poly(ethylene) (PE), Poly(fluoroacetate) (PFA), Poly(methyl methacrylate) (PMMA), Segmented Poly(urethane) (PU), Poly(vinyl chloride) (PVC), and silicone (Si)] as a mold in six subcutaneous pouches in the dorsal skin of New Zealand White rabbits. For rods apart from PFA, biotubes were constructed after 1 month of implantation by encapsulation around the Polymeric implants. The wall thickness of the biotubes ranged from about 50 to 200 microm depending on the implant material and were in the order PFA < PVC < PMMA < PU < PE. As for PE, PMMA, and PVC, the thickness increased after 3 months of implantation and ranged from 1.5-to 2-fold. None of the biotubes were ruptured when a hydrostatic pressure was gradually applied to their lumen up to 200 mmHg. The relationship between the intraluminal pressure and the external diameter, which was highly reproducible, showed a "J"-shaped curve similar to the native artery. The tissue mostly consisted of collagen-rich extracellular matrices and fibroblasts. Generally, the tissue was relatively firm and inelastic for Si and soft for PMMA. For PMMA, PE, and PVC the stiffness parameter (beta value; one of the indexes for compliance) of the biotubes obtained was similar to those of the human coronary, femoral, and carotid arteries, respectively. Biotubes, which possess the ability for wide adjustments in their matrices, mechanics, shape, and luminal surface design, can be applied for use as small-caliber blood vessels and are an ideal implant because they avoid immunological rejection.
Pieter J. Dijkstra - One of the best experts on this subject based on the ideXlab platform.
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structure formation and hydrogen bonding in all aliphatic Segmented coPolymers with uniform hard segments
Acta Biomaterialia, 2013Co-Authors: Ya I Odarchenko, Pieter J. Dijkstra, Jan Feijen, Niels J Sijbrandi, Ad J Kimenai, Rene Broos, Martin Rosenthal, Dimitri A IvanovAbstract:Abstract Fully aliphatic Segmented Poly(ether ester amide) coPolymers with uniform hard segments prepared by melt Polycondensation of α,ω-hydroxyl end-functionalized Polytetrahydrofuran and short glycine or β-alanine bisester–bisoxalamide units hold promise for biomedical applications. For Polymers with the hard block contents varying from 10% to 27%, differential scanning calorimetry and atomic force microscopy reveal a highly phase-separated morphology, with ribbon-like nanocrystals dispersed in the soft segment matrix. To relate the Polymer properties to the structure of the hard segment, the monomers were prepared and studied by optical and X-ray diffraction measurements. It was shown that the glycine and β-alanine carbonyl ester groups are tilted away from the oxalamide plane, which can affect the degradation rate via hydrolysis of the ester bond.
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synthesis morphology and properties of Segmented Poly ether ester amide s comprising uniform glycine or β alanine extended bisoxalamide hard segments
Polymer, 2012Co-Authors: Niels J Sijbrandi, Jan Feijen, Ad J Kimenai, Edwin P C Mes, Rene Broos, Georg Bar, Martin Rosenthal, Yaroslav Odarchenko, Dimitri A Ivanov, Pieter J. DijkstraAbstract:Segmented Poly(ether ester amide)s comprising glycine or β-alanine extended bisoxalamide hard segments are highly phase separated thermoplastic elastomers with a broad temperature independent rubber plateau. These materials with molecular weights, Mn, exceeding 30 × 103 g mol−1 are conveniently prepared by Polycondensation of preformed bisester–bisoxalamides and commercially available PTHF diols. FT-IR revealed strongly hydrogen bonded and highly ordered bisoxalamide hard segments with degrees of ordering between 73 and 99%. The morphology consists of fiber-like nano-crystals randomly dispersed in the soft Polymer matrix. The micro-structural parameters of the coPolymers were addressed by simultaneous small- and wide-angle X-ray scattering. It is shown that the crystals have strictly identical thickness, which is close to the contour length of the hard segment. The long dimension of the crystals is identified with the direction of the hydrogen bonds. The melting transitions of the hard segments are sharp, with temperatures up to 170 °C. The studied Polymers have an elastic modulus in the range of 139–170 MPa, a stress at break in the range of 19–31 MPa combined with strains at break of higher than 800%. The Segmented coPolymer comprising the β-alanine based bisoxalamide hard segment with a spacer of 6 methylene groups has a melting transition of 141 °C which is higher than the melting transition of its glycine analogue of 119 °C. Likewise, the fracture stress increased from 22 to 31 MPa when the glycine ester group in the hard segment was replaced with β-alanine. The improved thermal and mechanical properties of the latter Polymers is related to the crystal packing of the β-alanine based hard segments in the coPolymer compared to the packing of the hard segments comprising glycine ester groups
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Gas foaming of Segmented Poly(ester amide) films
Polymer, 2005Co-Authors: P.a.m. Lips, Pieter J. Dijkstra, I.w. Velthoen, Matthias Wessling, Jan FeijenAbstract:Biodegradable Segmented Poly(ester amide)s, based on dimethyl adipate, 1,4-butanediol and N,N?-1,2-ethanediyl-bis[6-hydroxy-hexanamide], with two distinct melting transitions were gas foamed using carbon dioxide (CO2). Polymer films were saturated with CO2 at 50 bar for 6 h after which the pressure was released. The samples were immersed in octane at the desired temperature after which foaming started immediately. Just above the lower melt transition the Polymers retain adequate mechanical properties and dimensional stability, while the chain mobility increased sufficiently to nucleate and expand gas cells during the foaming process. In this way semi-crystalline Poly(ester amide)s can be gas foamed below the flow temperature. Two Poly(ester amide)s with 25 mol% (PEA2,5-25) and 50 mol% (PEA2,5-50) of bisamide segment content were foamed at 70 and 105 °C, respectively. The storage modulus (G?) of both pure Polymers at the onset foaming temperature is 50?60 MPa. Closed-cell foams were obtained with a maximum porosity of not, vert, similar90%. The average pore size of PEA2,5-25 ranges from 77 to 99 ?m. In contrast, the average pore size of PEA2,5-50 is in between 2 and 4 ?m and can be increased to 100 ?m by lowering the CO2 saturation pressure to 20 bar. The porosity of PEA2,5-50 foams using this saturation pressure decreased to 70%
Pablo C Caracciolo - One of the best experts on this subject based on the ideXlab platform.
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Electrospinning of novel biodegradable Poly(ester urethane)s and Poly(ester urethane urea)s for soft tissue-engineering applications
Journal of materials science. Materials in medicine, 2009Co-Authors: Pablo C Caracciolo, Fabian Alejandro Buffa, Vinoy Thomas, Yogesh K. Vohra, Gustavo A. AbrahamAbstract:The development of biomimetic highly-porous scaffolds is essential for successful tissue engineering. Segmented Poly(ester urethane)s and Poly(ester urethane urea)s have been infrequently used for the fabrication of electrospun nanofibrous tissues, which is surprising because these Polymers represent a very large variety of materials with tailored properties. This study reports the preparation of new electrospun elastomeric Polyurethane scaffolds. Two novel Segmented Polyurethanes (SPU), synthesized from Poly(e-caprolactone) diol, 1,6-hexamethylene diisocyanate, and diester-diphenol or diurea-diol chain extenders, were used (Caracciolo et al. in J Mater Sci Mater Med 20:145–155, 2009). The spinnability and the morphology of the electrospun SPU scaffolds were investigated and discussed. The electrospinning parameters such as solution properties (Polymer concentration and solvent) and processing parameters (applied electric field, needle to collector distance and solution flow rate) were optimized to achieve smooth, uniform bead-free fibers with diameter (~700 nm) mimicking the protein fibers of native extracellular matrix (ECM). The obtained elastomeric Polyurethane scaffolds could be appropriate for soft tissue-engineering applications.
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effect of the hard segment chemistry and structure on the thermal and mechanical properties of novel biomedical Segmented Poly esterurethanes
Journal of Materials Science: Materials in Medicine, 2009Co-Authors: Pablo C Caracciolo, Fabian Buffa, Gustavo A. AbrahamAbstract:Two series of biomedical Segmented Polyurethanes (SPU) based on Poly(e-caprolactone) diol (PCL diol), 1,6-hexamethylene diisocyanate (HDI) or l-lysine methyl ester diisocyanate (LDI) and three novel chain extenders, were synthesized and characterized. Chain extenders containing urea groups or an aromatic amino-acid derivative were incorporated in the SPU formulation to strengthen the hard segment interactions through either bidentate hydrogen bonding or π-stacking interactions, respectively. By varying the composition of the hard segment (diisocyanate and chain extender), its structure was varied to investigate the structure-property relationships. The different chemical composition and symmetry of hard segment modulated the phase separation of soft and hard domains, as demonstrated by the thermal behavior. Hard segment association was more enhanced by using a combination of symmetric diisocyanate and urea-diol chain extenders. The hard segment cohesion had an important effect on the observed mechanical behavior. Polyurethanes synthesized using HDI (Series H) were stronger than those obtained using LDI (Series L). The latter SPU exhibited no tendency to undergo cold-drawing and the lowest ultimate properties. Incorporation of the aromatic chain extender produced opposite effects, resulting in Polyurethanes with the highest elongation and tearing energy (Series H) and the lowest strain at break (Series L). Since the synthesized biodegradable SPU possess a range of thermal and mechanical properties, these materials may hold potential for use in soft tissue engineering scaffold applications.
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Segmented Poly esterurethane urea s from novel urea diol chain extenders synthesis characterization and in vitro biological properties
Acta Biomaterialia, 2008Co-Authors: Pablo C Caracciolo, A A A De Queiroz, Olga Z Higa, Fabian Alejandro Buffa, Gustavo A. AbrahamAbstract:This work describes the preparation, physicochemical characterization, mechanical properties and in vitro biological properties of two bioresorbable aliphatic Segmented Poly(esterurethane urea)s (SPEUU) based on Poly(epsilon-caprolactone) diol (PCL diol), 1,6-hexamethylene diisocyanate and two novel urea-diol chain extenders. To strengthen the interactions through hydrogen bonding in the hard segments of SPEUU, novel chain extenders containing urea groups were synthesized and used in the SPEUU formulation. The different chemical structures of the chain extenders modulated the phase separation of soft and hard segments, as demonstrated by the thermal behavior. The hard segment association was enhanced using a diurea-diol chain extender. The biological interactions between the obtained materials and blood were studied by in vitro methods. Research on the protein adsorption, platelet adhesion and thrombus formation is presented. Studies of protein adsorption onto Polymeric surfaces showed that SPEUU adsorbed more albumin than fibrinogen. Studies on platelet adhesion and thrombus formation of SPEUU-coated coverslips indicated the antithrombogenic behavior of these surfaces. The synthesized SPEUU revealed no signs of cytotoxicity to Chinese hamster ovary cells, showing satisfactory cytocompatibility.