Pathiraja A. Gunatillake

The Commonwealth Scientific and Industrial Research Organisation, Canberra, Australian Capital Territory, Australia

Are you Pathiraja A. Gunatillake?

Claim your profile

Publications (48)160.87 Total impact

  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: 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 viability of about 40% for HUVEC cells. However, the viability was over 80% when the solution was diluted to 50% and below. The growth of HUVEC cells is similar to but not identical to that observed with tissue culture polystyrene standard (TCPS). The results from this in vitro study suggested that the PUs in the series degraded primarily due to the SS degradation and the cell viability of the accumulated acidic degradation products showed poor viability to HUVEC cells when tested undiluted, however particles released to the degradation medium showed cell viability over 80%.
    Frontiers in Bioengineering and Biotechnology 05/2015; 3. DOI:10.3389/fbioe.2015.00052
  • Source
  • [Show abstract] [Hide abstract]
    ABSTRACT: This study examined the suitability of a family of biodegradable polyurethanes (PUs) NovoSorb(TM) 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%. © 2014 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2014.
    Journal of Biomedical Materials Research Part B Applied Biomaterials 11/2014; 102(8). DOI:10.1002/jbm.b.33137 · 2.33 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Multi-functional mikto-arm star polymers containing three different arms [hydrophilic, SN-38-P(OEGMA8–9)11, cationizable, SN-38-P(DMAEMA)38 and hydrophobic, SN-38-P(BMA)26] were prepared by RAFT polymerization via an arm-first approach using a cleavable cross-linker. The star polymers were cleaved to the linear arms with tributylphosphine as a reducing agent. The decrease in molecular weight observed is consistent with the initial stars having approximately five arms. Blue fluorescence was observed when a solution of mikto-arm star was irradiated under a 365 nm light proving the retention of the SN-38 moiety during star formation by RAFT polymerization. Thus these polymer-drug conjugates can be considered as potential delivery vehicles for cancer therapy. The P(DMAEMA) arms can be quaternized using iodomethane, allowing star polymers to bind negatively charged small interfering RNA (siRNA) and potentially be used as a carrier for that material.
    Science China-Chemistry 07/2014; 57(7). DOI:10.1007/s11426-014-5128-5 · 1.52 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Aim: Influenza virus remains a major threat, with outbreaks continuing to occur. Few treatment options are available and drug resistance can emerge rapidly. New drugs that can quickly be adapted to virus mutations are needed. Several highly effective siRNAs targeting influenza that inhibit virus replication are known; however, effective delivery of these siRNAs remains a challenge. The aim of this study was to demonstrate the safety and efficacy of ABA triblock copolymer-delivered siRNA to inhibit influenza virus replication in vivo. Materials & methods: We report on the delivery of a siRNA targeting the influenza virus in chicken embryos using an ABA triblock copolymer prepared by reversible addition-fragmentation chain-transfer polymerization, containing a central cationic block and two outer hydrophilic polyethylene glycol blocks. Results: A significant reduction of virus titer was observed with the polymer/anti-influenza siRNA complexes, whereas the control with polymer/control siRNA complexes showed no effect. Conclusion: These data suggest that a reversible addition-fragmentation chain transfer-based siRNA delivery platform may be suitable for combating infectious diseases in vivo. Original submitted 21 December 2012; Revised submitted 10 May 2013.
    Nanomedicine 12/2013; DOI:10.2217/nnm.13.119 · 5.82 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: This study reports on the synthesis and characterization of a novel four-arm reagent and its use in the synthesis of core degradable star polymers and block copolymers using the reversible addition–fragmentation chain transfer (RAFT) polymerization process. The star RAFT polymers prepared from methyl methacrylate (MMA), styrene (ST) and N,N-dimethylacrylamide (DMA) were characterized by size exclusion chromatography (SEC). The PMMA star polymer was further polymerized with poly(ethylene glycol) methyl ether methacrylate (POEGMA8–9) to produce a star block copolymer. The core degradability of the star polymers (PMMA40)4, (PMMA80)4, (PS40)4, (PS80)4 and star block copolymer P[MMA46-b-(POEGMA8–9)46]4 under reductive conditions to cleave the disulfide linkages was demonstrated. The results demonstrated the complete degradation of the star polymer to produce linear polymer and confirmed the near equal degree of polymerization in each of the arms. The star polymer (PDMA80)4 degraded slowly under acidic and enzymatic conditions demonstrating that the ester linkage can also be degraded.
    Macromolecules 11/2013; 46(23):9181–9188. DOI:10.1021/ma402122z · 5.93 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Chain extension by diisocyanate condensation provides a versatile and convenient means for preparing block copolymers. We have utilized this chemistry to prepare reducible multiblock polycations for siRNA delivery. This approach, an alternative to oxidative coupling, was suitable for preparing multiblock polycations with defined molecular weight and architecture. The polymer, PEG-b-multi-(polyhexylurea-co-oligo-L-lysine)-b-PEG, was capable of electrostatically condensing siRNA to form nano-sized polyplexes across a broad compositional range. We demonstrated that the polyplexes enter the cells via endocytosis and interact with the endosome membrane leading to destabilization and hence endosome escape. Another feature of these polymers is their multiple intra-chain disulfide linkages. This enables weakening of the polyplex via chain scission within the cytosol's reductive environment. In addition to the controlled preparation of the polymer, the polyplexes were capable of delivering siRNA in vitro to silence greater than 50% green fluorescent protein expression with negligible toxicity.
    Acta biomaterialia 05/2013; 9(9). DOI:10.1016/j.actbio.2013.05.011 · 5.68 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: In this work a series of ABA tri-block copolymers was prepared from oligo(ethylene glycol) methyl ether methacrylate (OEGMA(475)) and N,N-dimethylaminoethyl methacrylate (DMAEMA) to investigate the effect of polymer composition on cell viability, siRNA uptake, serum stability and gene silencing. Reversible Addition-Fragmentation Chain Transfer (RAFT) polymerization was used as the method of polymer synthesis as this technique allows the preparation of well-defined block copolymers with low polydispersity. Eight block copolymers were prepared by systematically varying the central cationic block (DMAEMA) length from 38 to 192 monomer units and the outer hydrophilic block (OEGMA(475)) from 7 to 69 units. The polymers were characterized using size exclusion chromatography and (1)H NMR. Chinese Hamster Ovary-GFP and Human Embryonic Kidney 293 cells were used to assay cell viability while the efficiency of block copolymers to complex with siRNA was evaluated by agarose gel electrophoresis. The ability of the polymer-siRNA complexes to enter into cells and to silence the targeted reporter gene enhanced green fluorescent protein (EGFP) was measured by using a CHO-GFP silencing assay. The length of the central cationic block appears to be the key structural parameter that has a significant effect on cell viability and gene silencing efficiency with block lengths of 110-120 monomer units being the optimum. The ABA block copolymer architecture is also critical with the outer hydrophilic blocks contributing to serum stability and overall efficiency of the polymer as a delivery system.
    Biomaterials 07/2012; 33(30):7631-42. DOI:10.1016/j.biomaterials.2012.06.090 · 8.31 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: We present studies of the delivery of short interfering ribonucleic acid (siRNA) into a green fluorescent protein (GFP) expressing cell line, using lipid nanocarriers in cubic lyotropic liquid crystal form. These carriers are based on glycerol monooleate (GMO) and employ the use of varying concentrations of cationic siRNA binding lipids. The essential physicochemical parameters of the cationic lipid/GMO/siRNA complexes such as particle size, ζ otential, siRNA uptake stability, lyotropic mesophase behavior, cytotoxicity,and gene silencing efficiency were systematically assessed. We find that the lipid nanocarriers were effectively taken up by mammalian cells and that their siRNA payload was able to induce gene silencing in vitro. More importantly, it was found that the nonlamellar structure of some of the lipid nanocarrier formulations were more effective at gene silencing than their lamellar structured counterparts. The development of cationic lipid functionalized nonlamellar GMO-based nanostructured nanoparticles may lead to improved siRNA delivery vehicles.
    Molecular Pharmaceutics 07/2012; 9(9):2450-7. DOI:10.1021/mp200662f · 4.79 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: 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.
    The Journal of Physical Chemistry B 02/2012; 116(11):3551-6. DOI:10.1021/jp300239g · 3.38 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: We report a facile synthetic route to prepare polyurethanes with pendant sugar-moieties in the side-chain of the polymer through incorporation of diverse chain extenders capable of undergoing either copper catalyzed Huisgen 1,3-dipolar cycloaddition or thiol-ene click reactions.
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: This paper describes the synthesis and characterization of an injectable methacrylate functionalized urethane-based photopolymerizable prepolymer to form biodegradable hydrogels. The tetramethacrylate prepolymer was based on the reaction between two synthesized compounds, diisocyanato poly(ethylene glycol) and monohydroxy dimethacrylate poly(epsilon-caprolactone) triol. The final prepolymer was hydrated with phosphate-buffered saline (pH 7.4) to yield a biocompatible hydrogel containing up to 86% water. The methacrylate functionalized prepolymer was polymerized using blue light (450 nm) with an initiator, camphorquinone and a photosensitizer, N,N-dimethylaminoethyl methacrylate. The polymer was stable in vitro in culture media over the 28 days tested (1.9% mass loss); in the presence of lipase, around 56% mass loss occurred over the 28 days in vitro. Very little degradation occurred in vivo in rats over the same time period. The polymer was well tolerated with very little capsule formation and a moderate host tissue response. Human chondrocytes, seeded onto Cultispher-S beads, were viable in the tetramethacrylate prepolymer and remained viable during and after polymerization. Chondrocyte-bead-polymer constructs were maintained in static and spinner culture for 8 weeks. During this time, cells remained viable, proliferated and migrated from the beads through the polymer towards the edge of the polymer. New extracellular matrix (ECM) was visualized with Masson's trichrome (collagen) and Alcian blue (glycosaminoglycan) staining. Further, the composition of the ECM was typical for articular cartilage with prominent collagen type II and type VI and moderate keratin sulphate, particularly for tissue constructs cultured under dynamic conditions.
    Acta biomaterialia 03/2010; 6(9):3471-81. DOI:10.1016/j.actbio.2010.02.040 · 5.68 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Porous polyurethane networks containing covalently attached zwitterionic compounds dihydroxypolycaprolactone phosphorylcholine and 1,2-dihydroxy-N,N-dimethylamino-propane sulfonate have been prepared and characterised. Three polymers were prepared by reacting methyl 2,6-diisocyanato hexanoate functionalised D: -glucose as prepolymer A with either polycaprolactone triol alone or with addition of 10 mol% zwitterion as prepolymer B. All polymer compositions were mixed with 10 wt% hydrated gelatin beads. The cured polymers with the gelatin beads showed compression strengths that were still suitable for use in articular cartilage repair. The incorporation of zwitterions yielded more hydrophilic polymers that showed increased water absorption and increased porosity. After four months degradation in phosphate buffered saline, the polymers containing zwitterions had approximately 50% mass loss compared with 30% mass loss for that with polycaprolactone triol alone. All polymers were non-toxic in chondrocyte-based assays. Subcutaneous implantation of these polymers into rats confirmed that the polymers degraded slowly. Only a very mild inflammatory response was observed and the polymers were able to support new, well vascularised tissue formation.
    Journal of Materials Science Materials in Medicine 12/2009; 21(4):1081-9. DOI:10.1007/s10856-009-3955-2 · 2.38 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Biodegradable polyurethanes offer advantages in the design of injectable or preformed scaffolds for tissue engineering and other medical implant applications. We have developed two-part injectable prepolymer systems (prepolymer A and B) consisting of lactic acid and glycolic acid based polyester star polyols, pentaerythritol (PE) and ethyl lysine diisocyanate (ELDI). This study reports on the formulation and properties of a series of cross linked polyurethanes specifically developed for orthopaedic applications. Prepolymer A was based on PE and ELDI. Polyester polyols (prepolymer B) were based on PE and dl-lactic acid (PEDLLA) or PE and glycolic acid (PEGA) with molecular weights 456 and 453, respectively. Several cross linked porous and non-porous polyurethanes were prepared by mixing and curing prepolymers A and B and their mechanical and thermal properties, in vitro (PBS/37 degrees C/pH 7.4) and in vivo (sheep bi-lateral) degradation evaluated. The effect of incorporating beta-tricalcium phosphate (beta-TCP, 5 microns, 10 wt.%) was also investigated. The cured polymers exhibited high compressive strength (100-190 MPa) and modulus (1600-2300 MPa). beta-TCP improved mechanical properties in PEDLLA based polyurethanes and retarded the onset of in vitro and in vivo degradation. Sheep study results demonstrated that the polymers in both injectable and precured forms did not cause any surgical difficulties or any adverse tissue response. Evidence of new bone growth and the gradual degradation of the polymers were observed with increased implant time up to 6 months.
    Biomaterials 10/2008; 29(28):3762-70. DOI:10.1016/j.biomaterials.2008.06.021 · 8.31 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: To evaluate the biological response to two urethane-based adhesives used to repair full thickness meniscal wounds created in the partially vascularised (red-white) zone. An ovine bilateral meniscal defect model was used to evaluate the initial biological response of the meniscal cartilage and synovium over a 1-month period. A 10-mm full-thickness defect was created in the medial meniscus of each femorotibial joint. The defects were either left untreated or repaired using the urethane-based adhesives. Synovial fluid, synovial membrane and the meniscal cartilages were retrieved at necropsy for cytological and histological assessment. The ovine model proved to be a suitable system for examining meniscal repair. Untreated defects showed no tissue apposition or cellular healing response, whereas all eight defects repaired with the two urethane-based adhesive formulations showed signs of repair and tissue regeneration with indications of cell infiltration and new collagen deposition in and around the polymer. No adverse cellular response to the adhesives was observed in the meniscal defect or in the synovial membrane and fluid. Trauma to the knee commonly results in tears to the meniscal cartilage, with the majority of these occurring in the partially vascularised (red-white) or non-vascularised (white) zones of the meniscus. Repair, and subsequent healing, of these tears is poor because of the reduced vascularity and limited surgical access. The present data indicate that an ovine model is a suitable system for examining meniscal repair, and that development of urethane-based adhesives offers a strategy that may be clinically effective for the treatment of these injuries.
    Australian Veterinary Journal 07/2008; 86(6):229-34. DOI:10.1111/j.1751-0813.2008.00300.x · 1.02 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Biodegradable polyurethanes are typically prepared from polyester polyols, aliphatic diisocyanates and chain extenders. We have developed a degradable chain extender (DCE) based on dl-lactic acid and ethylene glycol to accelerate hard segment degradation. Three series of polyurethane elastomers were synthesised to investigate the effect of incorporating DCE on synthesis, mechanical and thermal properties and in-vitro degradation. Polyurethane soft segments were based on poly(epsilon-caprolactone) (PCL) polyol. The hard segment was based on either ethyl lysine diisocyanate or hexamethylene diisocyanate in combination with ethylene glycol or DCE. Polyurethanes were characterised by gel permeation chromatography, tensile testing (Instron) and differential scanning calorimetry. Polymer degradation in-vitro (phosphate buffered saline) was tested by measuring mass loss, change in molecular weight and amine concentration in degradation products at three different time points over a 1 year period. Incorporation of DCE did not affect thermal or mechanical properties but had an influence on the in-vitro degradation. All polyurethanes exhibited considerable molecular weight decrease over the test period, and DCE-based polyurethanes showed the highest mass loss. The presence of the DCE and the initial molecular weight of the polyurethane are the key factors responsible for high mass losses. Differential scanning calorimetry, amine group analysis and the observation that mass loss was directly proportional to hard segment weight percentage, strongly supported that the polyurethane hard segment is the most susceptible segment to degradation in these polyurethanes. The PCL-based soft segment appears to undergo little or no degradation under these test conditions.
    Biomaterials 01/2008; 28(36):5407-17. DOI:10.1016/j.biomaterials.2007.08.035 · 8.31 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The advent of injectable polymer technologies has increased the prospect of developing novel, minimally invasive arthroscopic techniques to treat a wide variety of ailments. In this study, we have synthesised and evaluated a novel polyurethane-based injectable, in situ curable, polymer platform to determine its potential uses as a tissue engineered implant. Films of the polymers were prepared by reacting two pentaerythritol-based prepolymers, and characterised for mechanical and surface properties, and cytocompatibility. This polymer platform displayed mechanical strength and elasticity superior to many injectable bone cements and grafts. Cytotoxicity tests using primary human osteoblasts, revealed positive cell viability and increased proliferation over a period of 7 days in culture. This favourable cell environment was attributed to the hydrophilic nature of the films, as assessed by dynamic contact angle (DCA) analysis of the sample surfaces. The incorporation of beta-TCP was shown to improve mechanical properties, surface wettability, and cell viability and proliferation, compared to the other sample types. SEM/EDX analysis of these surfaces also revealed physicochemical surface heterogeneity in the presence of beta-TCP. Based on preliminary mechanical analysis and cytotoxicity results, these injectable polymers may have a number or potential orthopaedic applications; ranging from bone glues to scaffolds for bone regeneration.
    Biomaterials 02/2007; 28(3):423-33. DOI:10.1016/j.biomaterials.2006.08.026 · 8.31 Impact Factor
  • Source
    Pathiraja Gunatillake, Roshan Mayadunne, Raju Adhikari
    [Show abstract] [Hide abstract]
    ABSTRACT: This chapter reviews recent developments in biodegradable synthetic polymers focusing on tailoring polymer structures to meet material specification for emerging applications such as tissue engineered products and therapies. Major classes and new families of synthetic polymers are discussed with regard to synthesis, properties and biodegradability, and known degradation modes and products are summarized based on studies reported during the past 10-15 years. Polyesters and their copolymers, polyurethanes, polyphosphazenes, polyanhydrides, polycarbonates, polyesteramides and recently developed injectable polymer systems based on polypropylenefumarates, polyurethanes and acrylate/urethane systems are reviewed. Polyesters such as polyglycolides, polylactides and their copolymers still remain as the major class of synthetic biodegradable polymers with products in clinical use. Although various copolymerization methods have addressed needs of different applications, release of acidic degradation products, processing difficulties and limited range of mechanical properties remains as major disadvantages of this family of polymers. Injectable polymers based on urethane and urethane/acrylate have shown great promise in developing delivery systems for tissue engineered products and therapies.
    Biotechnology annual review 02/2006; 12:301-47. DOI:10.1016/S1387-2656(06)12009-8
  • Source
    Tim Moore, Raju Adhikari, Pathiraja Gunatillake
    [Show abstract] [Hide abstract]
    ABSTRACT: Recent advances in the synthesis of poly(gamma-butyrolactone) have yielded homopolymers of up to 50,000 Mw from the low-cost monomer gamma-butyrolactone. This monomer has for the better part of a century been thought impossible to polymerise. Poly(gamma-butyrolactone) displays properties that are ideal for tissue-engineering applications and the bacterially derived equivalent, poly(4-hydroxybutyrate) (P4HB), has been evaluated for such uses. The glass transition temperature (-48 to -51 degrees C), melting point (53-60 degrees C), tensile strength (50 MPa), Young's modulus (70 MPa) and elongation at break (1000%) of P4HB make it a very useful biomaterial. Poly(gamma-butyrolactone) degrades to give gamma-hydroxybutyric acid which is a naturally occurring metabolite in the body and it has been shown to be bioresorbable. Investigation into the synthesis of poly(gamma-butyrolactone) has recently produced homo-oligomeric diols 400-1000 Mw that are suitable for reacting with diisocyanates to form polyurethanes. Biodegradable polyurethanes made from diols of polyglycolide (PGA) and poly(epsilon-caprolactone) (PCL) have the disadvantage of high glass transition and slow degradation, respectively. Poly(gamma-butyrolactone) can be thought of as being the missing link in the biodegradable polyester family immediately between PGA and PCL and displaying intermediate properties.
    Biomaterials 07/2005; 26(18):3771-82. DOI:10.1016/j.biomaterials.2004.10.002 · 8.31 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The long-term biostability of a novel thermoplastic polyurethane elastomer (Elast-Eon 2 80A) synthesized using poly(hexamethylene oxide) (PHMO) and poly(dimethylsiloxane) (PDMS) macrodiols has been studied using an in vivo ovine model. The material's biostability was compared with that of three commercially available control materials, Pellethane 2363-80A, Pellethane 2363-55D and Bionate 55D, after subcutaneous implantation of strained compression moulded flat sheet dumbbells in sheep for periods ranging from 3 to 24 months. Scanning electron microscopy, attenuated total reflectance-Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy were used to assess changes in the surface chemical structure and morphology of the materials. Gel permeation chromatography, differential scanning calorimetry and tensile testing were used to examine changes in bulk characteristics of the materials. The results showed that the biostability of the soft flexible PDMS-based test polyurethane was significantly better than the control material of similar softness, Pellethane 80A, and as good as or better than both of the harder commercially available negative control polyurethanes, Pellethane 55D and Bionate 55D. Changes observed in the surface of the Pellethane materials were consistent with oxidation of the aliphatic polyether soft segment and hydrolysis of the urethane bonds joining hard to soft segment with degradation in Pellethane 80A significantly more severe than that observed in Pellethane 55D. Very minor changes were seen on the surfaces of the Elast-Eon 2 80A and Bionate 55D materials. There was a general trend of molecular weight decreasing with time across all polymers and the molecular weights of all materials decreased at a similar relative rate. The polydispersity ratio, Mw/Mn, increased with time for all materials. Tensile tests indicated that UTS increased in Elast-Eon 2 80A and Bionate 55D following implantation under strained conditions. However, ultimate strain decreased and elastic modulus increased in the explanted specimens of all three materials when compared with their unimplanted unstrained counterparts. The results indicate that a soft, flexible PDMS-based polyurethane synthesized using 20% PHMO and 80% PDMS macrodiols has excellent long-term biostability compared with commercially available polyurethanes.
    Biomaterials 10/2004; 25(20):4887-900. DOI:10.1016/j.biomaterials.2004.01.004 · 8.31 Impact Factor

Publication Stats

1k Citations
160.87 Total Impact Points

Institutions

  • 1992–2014
    • The Commonwealth Scientific and Industrial Research Organisation
      Canberra, Australian Capital Territory, Australia
  • 1997
    • University of New South Wales
      • Graduate School of Biomedical Engineering
      Kensington, New South Wales, Australia