Frontiers in bioengineering and biotechnology, 2015
We have recently reported the mechanical properties and hydrolytic degradation behavior of a seri... more We have recently reported the mechanical properties and hydrolytic degradation behavior of a series of NovoSorb™ biodegradable polyurethanes (PUs) prepared by varying the hard segment (HS) weight percentage from 60 to 100. In this study, the in vitro degradation behavior of these PUs with and without extracellular matrix (ECM) coating was investigated under accelerated hydrolytic degradation (phosphate buffer saline; PBS/70°C) conditions. The mass loss at different time intervals and the effect of aqueous degradation products on the viability and growth of human umbilical vein endothelial cells (HUVEC) were examined. The results showed that PUs with HS 80% and below completely disintegrated leaving no visual polymer residue at 18 weeks and the degradation medium turned acidic due to the accumulation of products from the soft segment (SS) degradation. As expected the PU with the lowest HS was the fastest to degrade. The accumulated degradation products, when tested undiluted, showed ...
Biodegradable polyurethanes offer many advantages in designing polymers for biomedical implants i... more Biodegradable polyurethanes offer many advantages in designing polymers for biomedical implants including tissue engineering applications, with systems as injectable liquids and gels because of their potential to be delivered using arthroscopic techniques to defect sites 1 . Polyurethanes containing zwitterionic species have been shown to be more hydrophilic, improved biocompatibility and increased degradation 2 . In this study we report
The development of improved methods to allow the low energy production of cubic phase forming nan... more The development of improved methods to allow the low energy production of cubic phase forming nanoparticles (cubosomes) is highly desired. The lamellar to hexagonal and cubic phase change of these lipid nanoparticles has previously been induced via the lowering of pH and the addition of calcium ions to anionic lipid nanoparticles. We have developed a method to produce low polydispersity cubosomes without the requirement of high energy input such as shear, sonication or homogenization under physiological conditions. We have found that the simple addition of phosphate buffered saline solution to aqueous dispersions of cationic liposome vesicles made with phytantriol results in the spontaneous formation of cubosomes after vortex mixing. This finding demonstrates the potential of utilizing this technique to incorporate shear and temperature sensitive compounds into cubosomes under extremely mild conditions for biomedical and nanotechnological applications.
... E-mail: Christina.Ott@csiro.au; Thilak.Gunatillake@csiro.au; Fax: +61 3 9545 2446; Tel: +61 3... more ... E-mail: Christina.Ott@csiro.au; Thilak.Gunatillake@csiro.au; Fax: +61 3 9545 2446; Tel: +61 3 9545 2369. b Biointerface ... described the functionalization of RAFT6-derived copolymers with glucose using a thio-halogen click reaction as well as a nucleophilic substitution based on ...
Journal of Biomedical Materials Research Part B: Applied Biomaterials, 2014
This study examined the suitability of a family of biodegradable polyurethanes (PUs) NovoSorb dev... more This study examined the suitability of a family of biodegradable polyurethanes (PUs) NovoSorb developed for the vascular stent application. These segmented PUs are formulated to be biodegradable using degradable polyester and PU blocks. A series of PUs comprising different hard segment weight percentage ranging from 60 to 100 were investigated. The mechanical properties of the PUs were evaluated before and after gamma sterilization to assess their suitability for vascular implants. The real-time (PBS/37°C/pH 7.4) hydrolytic degradation studies were carried out under sterile conditions and PU glass transition temperature, molecular weight, and mass loss at 3, 6, and 9 months were determined. The viability and growth of Human Umbilical Vein Endothelial Cells (HUVEC) on PU surfaces were determined to assess the effect of PU degradation. The effect of coating of extracellular matrix (ECM) components on cell viability was also investigated. The study showed that the PUs possess excellent mechanical properties exhibiting high tensile strength (41-56 MPa) and tensile modulus (897-1496 MPa). The PU films maintained mechanical strength during the early phase of the degradation but lost strength at latter stages. The unmodified polymer surface of each PU promotes endothelial cell growth and proliferation, with a HUVEC retention rate of >70%.
Journal of Biomaterials Science, Polymer Edition, 1995
A series of novel polyurethane elastomers based on methylenediphenyl diisocyanate, 1,4-butanediol... more A series of novel polyurethane elastomers based on methylenediphenyl diisocyanate, 1,4-butanediol and the macrodiols, poly(hexamethylene oxide), poly(octamethylene oxide), and poly(decamethylene oxide) were implanted subcutaneously in sheep for periods of 3 and 6 months. The specimens that were subjected to 3 months of implantation were strained to 250% of their resting length, while those implanted for 6 months had no applied external strain. SEM examination of the explanted specimens revealed that the novel materials displayed resistance to environmental stress cracking. Proprietary materials, Pellethane 2363-80A, Biomer and Tecoflex EG-80A, which had been implanted under identical conditions, showed evidence of significant stress cracking. The extent of stress cracking in the 3-month strained experiment was similar to that from the 6-month unstrained experiment. Stress cracking was also observed in Pellethane 2363-55D, when implanted for 6 months (unstrained). Neither changes in molecular weight nor in tensile properties provided a clear indication of early susceptibility to degradation by environmental stress cracking.
... He is currently Project Leader, polymer development for medical implants and tissue engineeri... more ... He is currently Project Leader, polymer development for medical implants and tissue engineering applications. Darren Martin is a Materials Scientist with interests in structureproperty relationships in polymers, composites, and biomate-rials. ...
Frontiers in bioengineering and biotechnology, 2015
We have recently reported the mechanical properties and hydrolytic degradation behavior of a seri... more We have recently reported the mechanical properties and hydrolytic degradation behavior of a series of NovoSorb™ biodegradable polyurethanes (PUs) prepared by varying the hard segment (HS) weight percentage from 60 to 100. In this study, the in vitro degradation behavior of these PUs with and without extracellular matrix (ECM) coating was investigated under accelerated hydrolytic degradation (phosphate buffer saline; PBS/70°C) conditions. The mass loss at different time intervals and the effect of aqueous degradation products on the viability and growth of human umbilical vein endothelial cells (HUVEC) were examined. The results showed that PUs with HS 80% and below completely disintegrated leaving no visual polymer residue at 18 weeks and the degradation medium turned acidic due to the accumulation of products from the soft segment (SS) degradation. As expected the PU with the lowest HS was the fastest to degrade. The accumulated degradation products, when tested undiluted, showed ...
Biodegradable polyurethanes offer many advantages in designing polymers for biomedical implants i... more Biodegradable polyurethanes offer many advantages in designing polymers for biomedical implants including tissue engineering applications, with systems as injectable liquids and gels because of their potential to be delivered using arthroscopic techniques to defect sites 1 . Polyurethanes containing zwitterionic species have been shown to be more hydrophilic, improved biocompatibility and increased degradation 2 . In this study we report
The development of improved methods to allow the low energy production of cubic phase forming nan... more The development of improved methods to allow the low energy production of cubic phase forming nanoparticles (cubosomes) is highly desired. The lamellar to hexagonal and cubic phase change of these lipid nanoparticles has previously been induced via the lowering of pH and the addition of calcium ions to anionic lipid nanoparticles. We have developed a method to produce low polydispersity cubosomes without the requirement of high energy input such as shear, sonication or homogenization under physiological conditions. We have found that the simple addition of phosphate buffered saline solution to aqueous dispersions of cationic liposome vesicles made with phytantriol results in the spontaneous formation of cubosomes after vortex mixing. This finding demonstrates the potential of utilizing this technique to incorporate shear and temperature sensitive compounds into cubosomes under extremely mild conditions for biomedical and nanotechnological applications.
... E-mail: Christina.Ott@csiro.au; Thilak.Gunatillake@csiro.au; Fax: +61 3 9545 2446; Tel: +61 3... more ... E-mail: Christina.Ott@csiro.au; Thilak.Gunatillake@csiro.au; Fax: +61 3 9545 2446; Tel: +61 3 9545 2369. b Biointerface ... described the functionalization of RAFT6-derived copolymers with glucose using a thio-halogen click reaction as well as a nucleophilic substitution based on ...
Journal of Biomedical Materials Research Part B: Applied Biomaterials, 2014
This study examined the suitability of a family of biodegradable polyurethanes (PUs) NovoSorb dev... more This study examined the suitability of a family of biodegradable polyurethanes (PUs) NovoSorb developed for the vascular stent application. These segmented PUs are formulated to be biodegradable using degradable polyester and PU blocks. A series of PUs comprising different hard segment weight percentage ranging from 60 to 100 were investigated. The mechanical properties of the PUs were evaluated before and after gamma sterilization to assess their suitability for vascular implants. The real-time (PBS/37°C/pH 7.4) hydrolytic degradation studies were carried out under sterile conditions and PU glass transition temperature, molecular weight, and mass loss at 3, 6, and 9 months were determined. The viability and growth of Human Umbilical Vein Endothelial Cells (HUVEC) on PU surfaces were determined to assess the effect of PU degradation. The effect of coating of extracellular matrix (ECM) components on cell viability was also investigated. The study showed that the PUs possess excellent mechanical properties exhibiting high tensile strength (41-56 MPa) and tensile modulus (897-1496 MPa). The PU films maintained mechanical strength during the early phase of the degradation but lost strength at latter stages. The unmodified polymer surface of each PU promotes endothelial cell growth and proliferation, with a HUVEC retention rate of >70%.
Journal of Biomaterials Science, Polymer Edition, 1995
A series of novel polyurethane elastomers based on methylenediphenyl diisocyanate, 1,4-butanediol... more A series of novel polyurethane elastomers based on methylenediphenyl diisocyanate, 1,4-butanediol and the macrodiols, poly(hexamethylene oxide), poly(octamethylene oxide), and poly(decamethylene oxide) were implanted subcutaneously in sheep for periods of 3 and 6 months. The specimens that were subjected to 3 months of implantation were strained to 250% of their resting length, while those implanted for 6 months had no applied external strain. SEM examination of the explanted specimens revealed that the novel materials displayed resistance to environmental stress cracking. Proprietary materials, Pellethane 2363-80A, Biomer and Tecoflex EG-80A, which had been implanted under identical conditions, showed evidence of significant stress cracking. The extent of stress cracking in the 3-month strained experiment was similar to that from the 6-month unstrained experiment. Stress cracking was also observed in Pellethane 2363-55D, when implanted for 6 months (unstrained). Neither changes in molecular weight nor in tensile properties provided a clear indication of early susceptibility to degradation by environmental stress cracking.
... He is currently Project Leader, polymer development for medical implants and tissue engineeri... more ... He is currently Project Leader, polymer development for medical implants and tissue engineering applications. Darren Martin is a Materials Scientist with interests in structureproperty relationships in polymers, composites, and biomate-rials. ...
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