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Bioresorbable copolymers with tailored properies: innovative materials för soft tissuel engineering
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
2006 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The emerging need for new synthetic materials for soft tissue engineering applications encourages the search for innovative polymers having interesting properties. Ring-opening polymerization of lactones and lactides initiated by tin alkoxides has received particular attention due to the versatility of the method for building up well-defined biodegradable structures. The controlled reactions together with a careful choice of comonomers and copolymer composition make it possible to create materials with desired molecular architecture and properties.The aim of the work described in this thesis was to design aliphatic bioresorbable copolymers with new structures and controlled properties for potential application in soft tissue engineering. The first part of the work was focused on the surface properties of the materials synthesized for biomedical application. Solution-cast film triblock copolymers of L-lactide (LLA) and 1,5-dioxepan-2-one (DXO), subjected to thermal treatment have been studied. The effects of molecular weight, polymer composition, cooling rate, and casting solution concentration on the nanostructure surface morphology and topography have been investigated by atomic force microscopy (AFM). The surface characterization of the annealed triblock copolymers revealed well-defined fiber features formed as a result of a melt-induced micro-phase separation during crystallization. The dimensions and shape of the formations could be related to the copolymer composition and annealing conditions, and this makes it possible to create controlled and well-defined surface structure. The results of cell adhesion studies on annealed triblock copolymers indicate that these materials favor fibroblast growth and spreading, which makes them promising candidates for applications as bioresorbable membranes.In the next stage of the work, linear and network copolymers of ε-caprolactone (CL) and DXO with a controlled composition and controlled hydrophilicity have been synthesized. The molar fraction of DXO in the copolymers affected their mechanical, thermal and surface properties. The hydrophilicity was tailored by changing the monomer composition in the copolymers. The AFM measurements on the linear copolymers showed that short fibrillar structures were formed upon crystallization from the melt. The supple CL-DXO networks were easy to cast and could easily be removed from the mould surface, so that it is possible to use this material for embossing procedures without the risk of damaging the surface pattern during removal from the mould.

Place, publisher, year, edition, pages
Stockholm: KTH , 2006. , 70 p.
Series
Trita-FPT-Report, ISSN 1652-2443 ; 2006:18
Keyword [en]
poly(1, 5-dioxepan-2-one), poly(ε-caprolactone), poly(L-lactide), poly(trimethylene carbonate), triblock, network, cyclic tin alkoxide, controlled coordination-insertion ring-opening polymerization, thermoplastic elastomers
National Category
Polymer Chemistry
Identifiers
URN: urn:nbn:se:kth:diva-4042ISBN: 91-7178-378-4 (print)OAI: oai:DiVA.org:kth-4042DiVA: diva2:10528
Public defence
2006-06-16, Aal K2, Teknikringen 28, Stockholm, 10:00 (English)
Opponent
Supervisors
Note
QC 20100629Available from: 2006-06-07 Created: 2006-06-07 Last updated: 2010-06-29Bibliographically approved
List of papers
1. Well-organized phase-separated nanostructured surfaces of hydrophilic/hydrophobic ABA triblock copolymers
Open this publication in new window or tab >>Well-organized phase-separated nanostructured surfaces of hydrophilic/hydrophobic ABA triblock copolymers
2003 (English)In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 4, no 5, 1451-1456 p.Article in journal (Refereed) Published
Keyword
ATOMIC-FORCE MICROSCOPY, L-LACTIDE, THIN-FILM, 1, 5-DIOXEPAN-2-ONE, POLY(L-LACTIDE), NANOTOPOGRAPHY, MORPHOLOGIES, CELLS
National Category
Polymer Chemistry
Identifiers
urn:nbn:se:kth:diva-13190 (URN)10.1021/bm0341024 (DOI)000185386900047 ()
Note
QC 20100602Available from: 2010-06-02 Created: 2010-06-02 Last updated: 2017-12-12Bibliographically approved
2. Fibrillar structure of resorbable microblock copolymers based on 1,5-dioxepan-2-one and epsilon-caprolactone
Open this publication in new window or tab >>Fibrillar structure of resorbable microblock copolymers based on 1,5-dioxepan-2-one and epsilon-caprolactone
2003 (English)In: Journal of Polymer Science Part A: Polymer Chemistry, ISSN 0887-624X, E-ISSN 1099-0518, Vol. 41, no 15, 2412-2423 p.Article in journal (Refereed) Published
Abstract [en]

The copolymerization of 1,5-dioxepan-2-one (DXO) and E-caprolactone, initiated by a five-membered cyclic tin alkoxide initiator, was performed in chloroform at 60 degreesC. Copolymers with different molar ratios of DXO (25, 40, and 60%) were synthesized and characterized. C-13 NMR spectroscopy of the carbonyl region revealed the formation of copolymers with a blocklike structure. Differential scanning calorimetry measurements showed that all the copolymers had a single glass transition between -57 and -49 degreesC and a melting temperature in the range of 30.1-47.7 degreesC, both of which were correlated with the amount of DXO. An increase in the amount of DXO led to an increase in the glass-transition temperature and to a decrease in the melting temperature. Dynamic mechanical thermal analysis measurements confirmed the results of the calorimetric analysis, showing a single sharp drop in the storage modulus in the temperature region corresponding to the glass transition. Tensile testing demonstrated good mechanical properties with a tensile strength of 27-39 MPa and an elongation at break of up to 1400%. The morphology of the copolymers was examined with polarized optical microscopy and atomic force microscopy; the films that crystallized from the melt showed a short fibrillar structure (with a length of 0.05-0.4 mum) in contrast to the untreated solution-cast films. (C) 2003 Wiley Periodicals, Inc.

Keyword
1, 5-dioxepan-2-one (DXO), poly(epsilon-caprolactone), thermal properties, mechanical properties, morphology, RING-OPENING POLYMERIZATION
National Category
Other Engineering and Technologies not elsewhere specified
Identifiers
urn:nbn:se:kth:diva-13821 (URN)10.1002/pola.10781 (DOI)000184076500013 ()
Note
QC 20100629Available from: 2010-06-29 Created: 2010-06-29 Last updated: 2017-12-12Bibliographically approved
3. Potential tissue implants from the networks based on 1,5-dioxepan-2-one and epsilon-caprolactone
Open this publication in new window or tab >>Potential tissue implants from the networks based on 1,5-dioxepan-2-one and epsilon-caprolactone
2005 (English)In: Polymer journal, ISSN 0032-3896, Vol. 46, no 18, 6746-6755 p.Article in journal (Refereed) Published
Abstract [en]

The synthesis and characterization of degradable polymeric networks for biomedical applications was performed. Cross-linked films of poly(epsilon-caprolactone) (PCL) and poly(1,5-dioxepan-2-one) (PDXO) having various mole fractions of monomers and different cross-link densities were successfully prepared using 2,2'-bis-(epsilon-caprolactone-4-yl) propane (BCP) as cross-linking agent. Reaction parameters were carefully examined to optimise, the film-formin.,, conditions. Networks obtained were elastomeric materials. easy to cast and remove from the mould. Effect of CL content and cross-link density on the final properties of the polymer network was evaluated. High CL content or degree of cross-linking led to increase in Young's modulus and decrease in elongation at break. An increase in crystalline domains in films having a higher CL content was observed by optical microscopy. A greater thermal stability was observed in films having a high CL content. The hydrophilicity of the materials could be tailored by changing the CL content. The surface of the films became rougher with higher CL content.

Keyword
Characterization, Crosslinking, Degradation, Implants (surgical), Monomers, Plastic films, Synthesis (chemical), Tissue, 1, 5-dioxepan-2-one, Biomedical applications, Cross-linking agents, Organic polymers
National Category
Polymer Chemistry
Identifiers
urn:nbn:se:kth:diva-8817 (URN)10.1016/j.polymer.2005.06.038 (DOI)000231397200003 ()2-s2.0-23744514731 (Scopus ID)
Note
QC 20100629Available from: 2005-11-24 Created: 2005-11-24 Last updated: 2010-12-21Bibliographically approved
4. Resilient bioresorbable copolymers based on trimethylene carbonate, L-lactide, and 1,5-dioxepan-2-one
Open this publication in new window or tab >>Resilient bioresorbable copolymers based on trimethylene carbonate, L-lactide, and 1,5-dioxepan-2-one
2006 (English)In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 7, no 5, 1489-1495 p.Article in journal (Refereed) Published
Abstract [en]

The new combinations of monomers presented in this work were evaluated in order to create an elastic material for potential application in soft tissue engineering. Thermoplastic elastomers (TPE) of trimethylene carbonate (TMC) with L-lactide (LLA) and 1,5-dioxepan-2-one (DXO) have been synthesized using a cyclic five-membered tin alkoxide initiator. The block copolymers were designed in such a way that poly(trimethylene carbonate-co1,5-dioxepan-2-one) formed an amorphous middle block and the poly(L-lactide) (PLLA) formed semicrystalline terminal blocks. The amorphous middle block consisted of relatively randomly distributed TMC and DXO monomer units, and the defined block structure of the PLLA terminal segments was confirmed by C-13 NMR. The properties of the TMC-DXO-LLA copolymers were compared with those of triblock copolymers based either on LLA-TMC or on LLA-DXO. Differential scanning calorimetry and dynamic mechanical analysis data confirmed the micro-phase separation in the copolymers. The mechanical properties of the copolymers were evaluated using tensile testing and cycling loading. All of the copolymers synthesized showed a highly elastic behavior. The properties of copolymers could be tailored by altering the proportions of the different monomers.

Keyword
RING-OPENING POLYMERIZATION, EPSILON-CAPROLACTONE, TRIBLOCK COPOLYMERS, 1, 3-TRIMETHYLENE CARBONATE, THERMOPLASTIC ELASTOMER, BLOCK-COPOLYMERS, COPOLYESTERS, POLYLACTONES
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-13823 (URN)10.1021/bm060081c (DOI)000237593600015 ()2-s2.0-33744538110 (Scopus ID)
Note
QC 20100629Available from: 2010-06-29 Created: 2010-06-29 Last updated: 2017-12-12Bibliographically approved
5. Suitable materials for soft tissue reconstruction: In vitro studies of cell-triblock copolymer interactions
Open this publication in new window or tab >>Suitable materials for soft tissue reconstruction: In vitro studies of cell-triblock copolymer interactions
Show others...
2005 (English)In: Journal of bioactive and compatible polymers (Print), ISSN 0883-9115, E-ISSN 1530-8030, Vol. 20, no 6, 509-526 p.Article in journal (Refereed) Published
Abstract [en]

Keratinocytes and fibroblasts have been grown onto a series of triblock copolymers based on 1,5-dioxepan-2-one (DXO) and L-lactide (LLA). The molar ratio of DXO and LLA were varied in the copolymers. This resulted in different degrees of hydrophilicity, which in turn influenced the cell growth. On these surfaces, the morphological appearance of the cells with their cell movements and growth were investigated by means of scanning electron microscopy, time-lapse videomicroscopy and immunohistochemistry. All results clearly showed that the keratinocytes and fibroblasts adhered best to the most hydrophilic copolymers. A majority of the keratinocytes seeded on the most hydrophilic copolymer also presented a polarized morphology indicating a migration tendency. The cell growth onto these materials are interesting since a possible application for these unique materials is as polymeric membranes for guided cutaneous and/or periodontal tissue generation.

Keyword
triblock copolymers, hydrophilicity, cell culture, time-lapse video microscopy, cell morphology, cell movement, cell growth, tissue engineering, RING-OPENING POLYMERIZATION, L-LACTIDE, FUNCTIONAL-GROUPS, ADHESION, MIGRATION, BIOMATERIALS, 1, 5-DIOXEPAN-2-ONE, SURFACES, ORGANIZATION, BACTERIAL
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-13824 (URN)10.1177/0883911505058608 (DOI)000232940700001 ()2-s2.0-27844591666 (Scopus ID)
Note
QC 20100629Available from: 2010-06-29 Created: 2010-06-29 Last updated: 2017-12-12Bibliographically approved

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