Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
The influence of composition of porous copolyester scaffolds on reactions induced by irradiation sterilization
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.ORCID iD: 0000-0002-5850-8873
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
2008 (English)In: Biomaterials, ISSN 0142-9612, E-ISSN 1878-5905, Vol. 29, no 2, 129-140 p.Article in journal (Refereed) Published
Abstract [en]

In our previous work regarding radiation sterilization of porous scaffolds we have concluded that the composition and microstructure of the polymer chain are a key factor influencing the degradation reactions occurring upon irradiation. In this work we in contrast reported on the effects of high-energy irradiation on the thermal and mechanical properties. Electron beam (EB)- and T-irradiation sterilization were used in order to finalize the properties of a series of porous scaffolds comprised of different aliphatic polyester copolymers. The results presented here show that, for both sterilization methods, the crystallinity increased for all copolymers of 1,5-dioxepan-2-one (DXO) and L,L-lactide (LLA) at the minimum sterilization dose. The same was true of the P.-caprolactone (CL)- and LLA-containing copolymers upon EB sterilization, while a reduction in crystallinity were found upon gamma-irradiation. As was anticipated, it was shown that crystallinity also is a characteristic of the copolymer influencing the effects of the irradiation-induced reactions. Both the onset temperature and the temperature corresponding to the maximum rate of weight loss increased after irradiation and hence the thermal stability was increased. This is a result of a simultaneous lengthening of the chains by cross-linking reactions and a shortening by random chain-scissions occurring throughout the molecule, which lead to the formation of new endgroups with higher thermal stability. Scaffolds of crystalline polymers retained more of their initial tensile properties after irradiation compared to amorphous materials. The result previously published, showing that the composition was a key factor influencing the degradation reactions occurring upon irradiation, was augmented here.

Place, publisher, year, edition, pages
2008. Vol. 29, no 2, 129-140 p.
Keyword [en]
copolymer, sterilization, electron beam, gamma irradiation, POLY-EPSILON-CAPROLACTONE, ALIPHATIC POLYESTERS, THERMAL-DEGRADATION, L-LACTIDE, POLY(LACTIDE-CO-GLYCOLIDE) PLGA, STRUCTURAL INVESTIGATIONS, RADIATION STERILIZATION, POLY(L-LACTIDE) PLLA, MASS-SPECTROMETER, CYCLIC DIMER
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:kth:diva-13610DOI: 10.1016/j.biomaterials.2007.08.046ISI: 000251492200001Scopus ID: 2-s2.0-35548945835OAI: oai:DiVA.org:kth-13610DiVA: diva2:326182
Note
QC 20100622Available from: 2010-06-22 Created: 2010-06-22 Last updated: 2017-12-12Bibliographically approved
In thesis
1. Design of Functional Degradable Aliphatic Polyesters and Porous Tissue Engineering Scaffolds
Open this publication in new window or tab >>Design of Functional Degradable Aliphatic Polyesters and Porous Tissue Engineering Scaffolds
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The regeneration of damaged tissues or organs using porous scaffolds which act as temporary guides for the patient’s own cells, i.e. tissue engineering, is a means to overcome the shortcomings of current standard medical treatments. The large number of tissue engineering applications and the high demands on materials make it necessary to design materials and scaffolds with innovative characteristics tailored to suit specific applications. The purpose of the work presented in this thesis was to design aliphatic polyester (co)polymers and porous scaffolds in order to tailor material and scaffold properties and to control the property changes induced by radiation sterilization.

Porous scaffolds were created, with an emphasis on tailoring the scaffolds thermal and mechanical properties. Stannous octoate was used in ring-opening polymerizations of L,L-lactide (LLA), ε-caprolactone (CL) and 1,5-dioxepane-2-one (DXO) to attain three copolymer types with a wide assortment of monomer compositions. A solvent casting and salt leaching scaffold fabrication technique was developed, and highly porous scaffolds possessing a range of predetermined properties were obtained.

Highly porous tubular scaffolds of different designs for use in nerve regeneration were developed using copolymers of LLA, CL, DXO or trimethylene carbonate (TMC) and a versatile immersion coating and porogen leaching technique.

Reactions induced by electron beam and gamma irradiation were used to finalize the scaffold properties. By changing the nature of the radiation, the radiation dose, the type of monomers, the monomer composition and the chain microstructure, it was possible to alter the susceptibility and the degradation mechanisms of the polymers. Predicted end-properties were obtainable and the sterilization procedure was incorporated as a final step in the scaffold fabrication.

The free radical ring-opening polymerization of the cyclic ketene acetal 2-methylene-1,3-dioxe-5-pene was developed, a reaction mechanism was proposed and the reaction products were characterized as a first step towards the creation of an innovative multifunctional aliphatic polyester. The reaction mechanism was shown to be temperature-dependent and propagation was inhibited by the formation of an allylic radical in the ring-opening step. The primary reaction product at higher temperatures was the cyclic ester 3-vinyl-1,4-butyrolactone. At lower temperatures, the main product was oligomers of ring-opened and ring-retained repeating units.

Abstract [sv]

Regenerering av skadade vävnader eller organ genom användning av porösa bionedbrytbara implantat som temporära byggnadsställningar för patientens egna celler är ett sätt att lösa de tillkortakommanden som finns i dagens medicinska behandlingsmetoder. De många möjliga applikationerna för vävnadsersättning och de höga krav som ställs på materialen skapar ett behov av nya material med innovativa egenskaper. I denna avhandling används design av alifatiska polyetrar och porösa strukturer för att skräddarsy deras egenskaper och för att kontrollera de förändringar i egenskaper som sker när materialet strålningssteriliseras.

Porösa strukturer tillverkades med fokus på design av deras materialegenskaper. Genom sampolymerisation av L,L-laktid (LLA), ε-kaprolakton (CL) och 1,5-dioxepan-2-on (DXO) med utvalda sammansättningar och monomerkombinationer kunde dessa skräddarsys. Porösa strukturer med hög porositet och ett stort register av förutbestämbara mekaniska och termiska egenskaper framställdes via en utvecklad saltlakningsteknik.

Porösa tuber för nervregenerering, med olika design, utvecklades genom användning av sampolymerer av LLA, CL, DXO eller trimetylenkarbonat (TMC) och en mångsidig stöpnings- och saltlakningsteknik.

Genom att utnyttja de reaktioner som uppstod i de polymera materialen vid sterilisering, med elektron- eller gammastrålning, erhölls förutbestämbara slutgiltiga egenskaper för de porösa strukturerna. Detta uppnåddes genom att skapa material som påverkas på ett specifikt sätt vid bestrålning. Genom att förändra strålningstyp, strålningsdos, monomerer och sammansättningar ändrades känsligheten mot strålning och de reaktionsmekanismer som inducerats. Steriliseringsprocessen blir härmed inkorporerad som ett sista steg i framställningen av de porösa strukturerna.

En fri radikal ringöppningspolymerisation utvecklades för monomeren 2-metylen-1,3-dioxe-5-pen. Reaktionsprodukterna bestämdes och en reaktionsmekanism föreslogs, som ett första steg i framställningen av en innovativ multifunktionell polyester. Reaktionsmekanismen är temperaturberoende och propagering är hämmad på grund av stabiliteten av den allylradikal som bildas vid ringöppning. Vid högre reaktionstemperaturer bildades den cykliska estern 3-vinyl-1,4-butyrolakton som huvudprodukt. Vid lägre temperaturer var den huvudsakliga produkten oligomerer bestående av både ringöppnade och ringslutna repeterande enheter.

Place, publisher, year, edition, pages
Stockholm: KTH, 2009. 58 p.
Series
Trita-CHE-Report, ISSN 1654-1081 ; 2009:20
Keyword
Ring-opening polymerization, Stannous octoate, 2, 2’-azoisobutyronitrile, 1, 5-dioxepane-2-one, ε-caprolactone, L-lactide, Trimethylene carbonate, 2-methylene-1, 3-dioxe-5-pene, Copolymer, Porous scaffold, Porous tubular scaffold, Electron beam, Gamma irradiation
National Category
Polymer Chemistry
Identifiers
urn:nbn:se:kth:diva-10368 (URN)978-91-7415-309-5 (ISBN)
Public defence
2009-05-29, E1, KTH, Lindstedtsvägen 3, Stockholm, 10:00 (English)
Opponent
Supervisors
Note
QC 20100805Available from: 2009-05-14 Created: 2009-05-08 Last updated: 2010-08-05Bibliographically approved
2. Macromolecular design and architecture of aliphatic polyesters
Open this publication in new window or tab >>Macromolecular design and architecture of aliphatic polyesters
2008 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

Public health care has reached a level where tissue or organ reconstruction by means of biodegradable short-term implants via e.g. tissue engineering will be practicable in the near future. The vital issue now is to be able to reproducibly fabricate and design new materials with the appropriate properties and three-dimensional shape, and to facilitate their sterilization. In this thesis, macromolecular design and polymer architecture techniques are used to synthesize well-defined polymers with narrow molecular weight distributions (MWD), and to control the reactions upon sterilization, and the degradation rate and profile.

A model system for the ring-opening polymerization of L-lactide (LLA) initiated by a spirocyclic tin initiator was developed to synthesize star-shaped polymers. It was shown that an increase in temperature and a decrease in the dielectrical constant of the solvents increased the reaction rate. The versatility of the spirocyclic tin initiator system was subsequently established, by homopolymerization of ε-caprolactone (CL) and 1,5-dioxepan-2-one (DXO) and this system was compared with a conventional system using stannous octoate (Sn(Oct)2) and pentaerythritol ethoxylate. Two different strategies were assessed for the two initiator systems for the synthesis of copolymers that are random or blocky in their nature. Random copolymers with distinct sequence lengths were synthesized using both initiator systems, together with block poly(DXO-co-LLA) and poly(CL-co-LLA) with narrow MWD.

Three different types of copolymers of LLA, CL and DXO were synthesized using Sn(Oct)2 and ethylene glycol. A solvent casting and particulate leaching technique was developed and applied to construct porous scaffolds of the copolymers. The porous scaffolds were subsequently sterilized using electron beam or γ-irradiation and it was shown that the reactions induced by radiation can be used to tailor the end-properties of the materials.

Homo- and copolymers of CL and DXO with different macromolecular designs (triblock and multiblock) and different polymer architectures (linear and cross-linked) were synthesized and degraded in a phosphate buffer solution for up to 364 days. By altering the network composition, the release pattern of acidic degradation products was controlled, where an increase in DXO content led to an increase in the release of both monomeric hydroxy-acids. Varying the distribution of the more hydrolysis-susceptible DXO-sequences in the linear copolymers also enabled the amount of monomeric hydroxy acids released to be controlled, where the triblock copolymer showed the highest release.

Place, publisher, year, edition, pages
Stockholm: KTH, 2008. 62 p.
Series
Trita-CHE-Report, ISSN 1654-1081 ; 2008:11
Keyword
Ring-opening polymerization, L-lactide, 1, 5-dioxepane-2-one, ε-caprolactone, Polymerization kinetics, Star-shaped architecture, Spirocyclic tin initiator
National Category
Polymer Chemistry
Identifiers
urn:nbn:se:kth:diva-4657 (URN)978-91-7178-883-2 (ISBN)
Public defence
2008-03-20, F3, KTH, Lindstedtsvägen 26, Stockholm, 09:00
Opponent
Supervisors
Note
QC 20100901Available from: 2008-03-03 Created: 2008-03-03 Last updated: 2010-09-01Bibliographically approved

Open Access in DiVA

No full text

Other links

Publisher's full textScopus

Authority records BETA

Odelius, Karin

Search in DiVA

By author/editor
Odelius, KarinPlikk, PeterAlbertsson, Ann-Christine
By organisation
Fibre and Polymer Technology
In the same journal
Biomaterials
Engineering and Technology

Search outside of DiVA

GoogleGoogle Scholar

doi
urn-nbn

Altmetric score

doi
urn-nbn
Total: 97 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf