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Degradable Porous Scaffolds from Various L-Lactide and Trimethylene Carbonate Copolymers Obtained by a Simple and Effective Method
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.ORCID iD: 0000-0002-1922-128X
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
2009 (English)In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 10, no 1, 149-154 p.Article in journal (Refereed) Published
Abstract [en]

A simple and effective method of fabricating scaffolds with open pore structures was successfully used on several copolymers. The method, which is straightforward and fast, was developed to overcome problems such as low pore interconnectivity and to achieve thick three-dimensional scaffolds. Copolymers are of particular interest because it is possible to tune their mechanical and degradable properties, and in this work, copolymers of L-lactide (LLA) and trimethylene carbonate (TMC) were synthesized through ring-opening polymerization. The copolymers formed had molecular weights ranging from close to 60000 g/mol to over 300000 g/mol and they were composed of 12-55 molar percentages of TMC and 88-45 molar percentages of LLA. The synthesized copolymers were evaluated as scaffold materials using a combined phase separation and particulate leaching technique, in which sugar templates were used as the leachable porosifiers. Differences in molecular weights, molar compositions, and degrees of crystallinity were all factors that influenced the properties of the prepared scaffolds. The copolymers with high LLA contents and high degrees of crystallinity were best suited for the scaffold fabrication technique used and gave degradable scaffolds with interconnected pores.

Place, publisher, year, edition, pages
2009. Vol. 10, no 1, 149-154 p.
Keyword [en]
ring-opening polymerization, 1, 5-dioxepan-2-one, architectures, polyesters, initiator, solvents, ester
National Category
Polymer Chemistry
Identifiers
URN: urn:nbn:se:kth:diva-18096DOI: 10.1021/bm801052mISI: 000262399600020Scopus ID: 2-s2.0-58549092276OAI: oai:DiVA.org:kth-18096DiVA: diva2:336142
Note
QC 20100525Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2017-12-12Bibliographically approved
In thesis
1. Synthesis of Biomedical Polymers and Scaffold Design
Open this publication in new window or tab >>Synthesis of Biomedical Polymers and Scaffold Design
2008 (English)Licentiate thesis, comprehensive summary (Other scientific)
Abstract [en]

This work has focused on the development of new improved synthesis methods of biodegradable aliphatic polymers and on the preparation of porous scaffolds for tissue engineering applications. The aim of the first part of the work was the synthesis of poly(p-dioxanone) (PPDX) homopolymers with high molecular weights using the cyclic tin alkoxide initiator 1-di-n-butyl-1-stanna-2,5-dioxacyclopentane. PPDX is a polymer with both mechanical properties and a degradation rate suitable for many biomedical applications. The polymerizations were carried out in bulk and the results were compared with polymerizations using tin (II) 2-ethylhexanoate (stannous octoate, Sn(Oct)2), a co-initiator which has previously been found effective in the polymerization of p-dioxanone (PDX). The hypothesis of this work was that the cyclic tin alkoxide initiator would bring several benefits to the synthesis of PPDX. It has been shown to catalyze low amounts of transesterfication reactions and materials with very low amounts of tin residues have been synthesized using an efficient purification technique. Our work demonstrated that the cyclic tin alkoxide initiator is indeed a promising alternative in the synthesis of PPDX with high inherent viscosities. Under the appropriate reaction conditions, PPDX polymers with inherent viscosities over, or around, 1 dL/g were synthesized. One of the most interesting materials made had an inherent viscosity of 1.16 dL/g, a strain-at-break of 515 %, a stress-at-break of 43 MPa, and was synthesized using the cyclic tin alkoxide initiator.

As a second part of this work, copolymers of L-lactide (LLA) and trimethylene carbonate (TMC) were synthesized using either Sn(Oct)2 with ethylene glycol or the cyclic tin alkoxide initiator 1-di-n-butyl-1-stanna-2,5-dioxacyclopentane. The copolymers, which had molecular weights ranging from close to 60 000 g/mol to over 300 000 g/mol, were composed of 12 to 55 molar percentages of TMC and 88 to 45 molar percentages of LLA. The copolymers were evaluated as porous scaffold materials intended for tissue engineering, using a combined phase separation and particulate leaching technique, in which sugar templates were used as the leachable porogens. The aim of this part of the work was to develop a simple and effective method for preparing scaffolds with high porosities and well interconnected pores and to overcome problems with formation of a solid surface side and limitations in scaffold thickness. The preparation method was successfully used on several copolymers. Differences in molecular weights, molar compositions and degrees of crystallinity were all factors which influenced the properties of the prepared scaffolds. Copolymers with TMC contents of up to 55 % were successfully used in the preparation of scaffolds. The results indicated however that materials with lower TMC contents and higher degrees of crystallinity in many cases were better suited for the combined phase separation and particulate leaching technique used.

Place, publisher, year, edition, pages
Stockholm: KTH, 2008. 42 p.
Series
Trita-CHE-Report, ISSN 1654-1081 ; 2008:74
Keyword
ring-opening polymerization, tin alkoxide initiator, stannous octoate, poly(p-dioxanone), copolymer, L-lactide, trimethylene carbonate, degradable porous scaffold
National Category
Polymer Chemistry
Identifiers
urn:nbn:se:kth:diva-9674 (URN)978-91-7415-185-5 (ISBN)
Presentation
2008-12-11, K1, Teknikringen 56, 100 44, Stockholm, KTH, 09:15 (English)
Supervisors
Note
QC 20101125Available from: 2008-11-28 Created: 2008-11-26 Last updated: 2010-11-25Bibliographically approved
2. Synthetic Pathways to Aliphatic Polyesters and Scaffold Design
Open this publication in new window or tab >>Synthetic Pathways to Aliphatic Polyesters and Scaffold Design
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

As the field of tissue engineering progresses, a continuous development of scaffold fabrication techniques and suitable degradable materials is required to obtain scaffolds with tunable characteristics. This thesis has focused on the development of pathways to synthesize degradable aliphatic polyesters and on the design of highly porous scaffolds from this class of materials.

Porous scaffolds aimed for tissue engineering applications were successfully created from poly(L-lactide-co-trimethylene carbonate) copolymers, with an emphasis on obtaining highly porous scaffolds, possessing well interconnected pores throughout the scaffold structure. To obtain the porous structures, sugar templates were used in a combined phase separation and porogen leaching scaffold fabrication technique. The technique developed for these materials was simple and versatile and scaffolds of up to 55 mol% TMC were effectively produced.

Poly(p-dioxanone) (PPDX) is a degradable polyether-ester with a comparatively short degradation time, making it useful for many biomedical applications. A synthetic route to PPDX polymers was developed using the cyclic tin (IV) alkoxide initiator 1-di-n-butyl-1-stanna-2,5-dioxacyclopentane. Our work demonstrated that the polymerization route with this initiator is indeed a promising alternative to the more commonly used stannous octoate. Under the appropriate reaction conditions, PPDX polymers with inherent viscosities over 1 dL/g and promising mechanical properties were synthesized.

The design of functional materials is an important step towards fulfilling the material demands within tissue engineering. The free radical ring-opening polymerization of the cyclic ketene acetal monomer 2-methylene-1,3-dioxe-5-pene was developed. As a first step towards the creation of a new multifunctional polyester, the reaction mechanism and the reaction products at different reaction temperatures were mapped. At higher reaction temperatures, the main reaction product was the cyclic ester 3-vinyl-1,4-butyrolactone. At lower reaction temperatures, low molecular weight oligomeric products of both ring-opened and ring-retained repeating units were formed.

Combining scaffold design with sugar templates and the synthesis of functional polyesters led to the creation of highly porous functional scaffolds. Both functional scaffolds and functional films were obtained from poly(ɛ-caprolactone) and poly(L-lactide), synthesized using multifunctional poly(but-2-ene-1,4-diyl malonate) and stannous octoate as initiating system. The mechanical characteristics of the cross-linkable scaffolds and films were evaluated by cyclic compression test under physiological conditions and by cyclic tensile tests.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2011
Series
Trita-CHE-Report, ISSN 1654-1081 ; 2011:36
National Category
Polymer Chemistry
Identifiers
urn:nbn:se:kth:diva-33875 (URN)978-91-7415-997-4 (ISBN)
Public defence
2011-06-10, F3, Lindstedtsvägen 26, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Note
QC 20110527Available from: 2011-05-27 Created: 2011-05-20 Last updated: 2011-05-27Bibliographically approved

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