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Porous degradable polyester scaffolds
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
2006 (English)Licentiate thesis, comprehensive summary (Other scientific)
Abstract [en]

Tissue engineering is a growing research field in which degradable porous scaffolds are used to regenerate tissue from the patients own cells. The problems due to donor shortage or the lack of full property restoration from prosthetic implants can thereby be overcome. It is important that the polymers used in tissue engineering, as in any medical application, have well controlled properties. Equally important is the ability to tailor these properties to suite a specific application. The development of fabrication processes that enables tailoring, without any uncontrolled changes in characteristics, is thereby imperative.

In this thesis, the creation of porous scaffolds focusing on tailoring and customizing the scaffold properties is described. Tailoring was achieved by selecting the proper monomers and their compositions when copolymerizing different cyclic aliphatic ester monomers and an ether-ester monomer. Porous structures applicable for both soft and hard tissue regeneration were obtained comprising a range of predetermined mechanical and thermal properties. In detail, stannous octoate was used as the catalyst in ring-opening polymerization of L,L-lactide (LLA), ε-caprolactone (CL) and 1,5-dioxepane-2-one (DXO) to attain the wide assortment of copolymers with different monomers and monomer compositions. Highly porous scaffolds having well interconnected pores were obtained through the development of a versatile solvent casting and porogen leaching technique.

The reactions induced by high energy radiation in the form of electron beam and gamma-ray were used to finalize the scaffold properties. This was achieved by creating polymers possessing predetermined reaction mechanisms when irradiated. Changes in the nature of the radiation, the radiation dose, the type of monomers, the composition and thus the microstructure of the chain gave ways to alter the susceptibility and the reaction mechanism of the polymers. Thus, predicted end-products are obtainable and the sterilization procedure is consequently incorporated as a final step in the scaffold fabrication.

Place, publisher, year, edition, pages
Stockholm: KTH , 2006. , 48 p.
Series
Trita-FPT-Report, ISSN 1652-2443 ; 2006:15
Keyword [en]
aliphatic polyester, copolymer, porous scaffold, ring-opening polymerization, electron beam, gamma irradiation
Keyword [sv]
Polymerteknologi
National Category
Chemical Sciences
Identifiers
URN: urn:nbn:se:kth:diva-3960ISBN: 91-7178-366-0 (print)OAI: oai:DiVA.org:kth-3960DiVA: diva2:10191
Presentation
2006-06-01, Sal E2, Huvudbyggnaden, KTH, Lindstedtsvägen 3, Stockholm, 09:00
Opponent
Supervisors
Note
QC 20101123Available from: 2006-05-11 Created: 2006-05-11 Last updated: 2010-11-23Bibliographically approved
List of papers
1. Elastomeric hydrolyzable porous scaffolds: Copolymers of aliphatic polyesters and a polyether-ester
Open this publication in new window or tab >>Elastomeric hydrolyzable porous scaffolds: Copolymers of aliphatic polyesters and a polyether-ester
2005 (English)In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 6, no 5, 2718-2725 p.Article in journal (Refereed) Published
Abstract [en]

Porous scaffolds of 1,5-dioxepan-2-one (DXO), L-lactide (LLA), and epsilon-caprolactone (CL) were prepared by a solvent casting, salt particulate leaching technique in which the composites were detached from their mold using a novel methanol swelling procedure. By incorporating DXO segments into polymers containing LLA or CL, an increase in hydrophilicity is achieved, and incorporating soft amorphous domains in the crystalline sections enables tailoring of the mechanical properties. The porosities of the scaffolds ranged from 89.2% to 94.6%, and the pores were shown to be interconnected. The materials were synthesized by bulk copolymerization of 1,5-dioxepan-2-one (DXO), L-lactide (LLA), and epsilon-caprolactone (CL) using stannous 2-ethylhexanoate as catalyst. The copolymers formed varied in structure; poly(DXO-co-CL) is random in its arrangement, whereas poly(DXO-co-LLA) and poly(LLA-co-CL) are more blocky in their structures.

Keyword
biodegradable polymeric scaffolds, epsilon-caprolactone, l-lactide, mechanical-properties, phase-separation, 1, 5-dioxepan-2-one, degradation, poly(epsilon-caprolactone), poly(l-lactide), polylactones
National Category
Polymer Chemistry
Identifiers
urn:nbn:se:kth:diva-14414 (URN)10.1021/bm050190b (DOI)000231899200042 ()2-s2.0-25844458172 (Scopus ID)
Note
QC 20100805Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2017-12-12Bibliographically approved
2. Finalizing the properties of porous scaffolds of aliphatic polyesters through radiation sterilization
Open this publication in new window or tab >>Finalizing the properties of porous scaffolds of aliphatic polyesters through radiation sterilization
2006 (English)In: Biomaterials, ISSN 0142-9612, E-ISSN 1878-5905, Vol. 27, no 31, 5335-5347 p.Article in journal (Refereed) Published
Abstract [en]

Porous scaffolds made of various L,L-lactide (LLA), 1,5-dioxepane-2-one (DXO) and epsilon-caprolactone (CL) copolymers were sterilized by EB- and gamma-irradiation. Differences in the comonomers, composition and the microstructure of the starting materials were used to influence the degradation mechanism and susceptibility towards irradiation and by this means to achieve sterilized scaffolds with predicted end-properties. The chemical changes and the formation of low-molecular-weight products were determined by SEC, H-1 nuclear magnetic resonance (NMR), C-13 NMR and gas chromatography-mass spectrometry (GC-MS). The degradation mechanism changed from random chain scission to cross-linking depending on the choice of monomers, the copolymer composition and the monomer sequences. Copolymerization of LLA with small amounts of CL or DXO increased the stability compared to that of the LLA homopolymer. Changing DXO to CL in a LLA copolymer also increased the stability. The type of radiation and the microstructure of the copolymer chains determined which of the monomer sequences were more prone to degrade. The most abundant low-molecular-weight product identified after sterilization was DXO monomer. Traces of LLA and CL monomers were also identified. Modification of the copolyester microstructure changed the degradation mechanism and the susceptibility towards irradiation. This allows the use of radiation sterilization to finalize the scaffold properties.

Keyword
electron beam, gamma irradiation, scaffold, copolymer, polycaprolactone, polylactic acid
National Category
Polymer Chemistry Polymer Technologies
Identifiers
urn:nbn:se:kth:diva-14416 (URN)10.1016/j.biomaterials.2006.06.024 (DOI)000240611000001 ()2-s2.0-33746216928 (Scopus ID)
Note

QC 20150720

Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2017-12-12Bibliographically approved

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