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Porous scaffolds from high molecular weight polyesters synthesized via enzyme-catalyzed ring-opening polymerization
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
2006 (English)In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 7, no 9, 2531-2538 p.Article in journal (Refereed) Published
Abstract [en]

Several aliphatic polyesters have been synthesized until now using enzyme-catalyzed ring-opening polymerization (ROP) of different lactones, although their molecular weight, hence mechanical strength, was not sufficient enough to fabricate porous scaffolds from them. To achieve this target, 1,5-dioxepan-2-one (DXO) and epsilon-caprolactone (CL) were polymerized in bulk with Lipase CA as catalyst at 60 degrees C, and porous scaffolds were prepared from the polymers obtained thereof using a salt leaching technique. The CL/DXO molar feed ratio was varied from 1.5 to 10, and the reactivity ratios of CL and DXO were determined using the Kelen-Tudos method under such conditions of polymerization. NMR results showed a slightly lower CL/DXO molar ratio in the copolymers than in the feed due to high reactivity of DXO toward Lipase CA catalysis. The crystallinity of the PCL segment of the copolymers was affected by the presence of soft and amorphous DXO domains. The copolymers having high CL content were thermally more stable. The porosity of the scaffolds was in the range 82-88%, and the SEM analysis showed interconnected pores in the scaffolds. Of the two parameters which could affect the mechanical properties, viz., the copolymer composition and the scaffold pore size, the pore size showed a significant effect on the mechanical properties of the scaffolds. The porous scaffolds developed in this way for tissue engineering are free from toxic organometallic catalyst residues, and they are highly suitable for biomedical applications.

Place, publisher, year, edition, pages
2006. Vol. 7, no 9, 2531-2538 p.
Keyword [en]
Aliphatic polyester; Enzyme-catalyzed ring-opening polymerization; Kelen-Tudos method; Salt leaching technique; Composition; Enzyme kinetics; Leaching; Molecular weight distribution; Nuclear magnetic resonance spectroscopy; Porosity; Ring opening polymerization; Scanning electron microscopy; Synthesis (chemical); Polyesters; 1, 5 dioxepan 2 one; aliphatic compound; copolymer; lactone; lipase B; organometallic compound; polycaprolactone; polyester; pyran derivative; unclassified drug; article; biomedicine; carbon nuclear magnetic resonance; catalysis; chemical composition; chemical structure; controlled study; gel permeation chromatography; leaching; mathematical computing; molecular weight; polymerization; porosity; priority journal; proton nuclear magnetic resonance; ring opening; scanning electron microscopy; synthesis; temperature measurement; tensile strength; thermogravimetry; thermostability; tissue engineering; Biocompatible Materials; Biotechnology; Catalysis; Chromatography; Lipase; Magnetic Resonance Spectroscopy; Microscopy, Electron, Scanning; Molecular Weight; Polyesters; Polymers; Salts; Tensile Strength; Thermodynamics; Thermogravimetry; Tissue Engineering
National Category
Polymer Chemistry
Identifiers
URN: urn:nbn:se:kth:diva-7008DOI: 10.1021/bm060309wISI: 000240403300011Scopus ID: 2-s2.0-33749547412OAI: oai:DiVA.org:kth-7008DiVA: diva2:11882
Note
QC 20100818Available from: 2007-04-20 Created: 2007-04-20 Last updated: 2017-12-14Bibliographically approved
In thesis
1. Aliphatic Polyesters for Soft Tissue Engineering: Development from Conventional Organometallic to Novel Enzymatic Catalysis
Open this publication in new window or tab >>Aliphatic Polyesters for Soft Tissue Engineering: Development from Conventional Organometallic to Novel Enzymatic Catalysis
2007 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

The development of macromolecules with defined structure and properties, aimed specifically for biomedical applications, has resulted in diverse biodegradable polymers with advanced architectures. Among them, aliphatic polyesters synthesized by ring-opening polymerization (ROP) of lactones and lactides have a leading position due to their good mechanical properties, hydrolyzability and biocompatibility. To achieve tailored properties and controlled architecture, the technique for ROP of lactones and lactides has been continuously refined in the past years. Enzyme-catalyzed ROP is one of the most promising tools, which avoids the use of toxic organometallic catalysts and brings a “green-chemistry” appeal with it. In the work described in this thesis, enzyme-catalyzed ROP of 1,5-dioxepan-2-one (DXO), ε-caprolactone (CL) and lactides (L-, D- and D,L-lactide) was performed in bulk using Lipases from different sources. The effects of enzyme concentration, polymerization temperature and reaction water content on the monomer conversion and the polymer molecular weight during DXO polymerization were studied, and the role of water as initiator was confirmed. Terminal functionalized, block, comb and star polymers were synthesized using different alcohols as initiator in the enzyme-catalyzed ROP of DXO, CL or lactides under strictly anhydrous conditions. The effect of simultaneous and sequential copolymerization of DXO and CL on the micro-block structure of the copolymers was studied and the reactivity ratios of DXO and CL were determined under Lipase catalysis. High molecular weight copolymers of DXO and CL thus obtained were fabricated into porous scaffolds for tissue implant applications. Enzymatic degradation and alkaline hydrolysis of lactides was performed to study the effect of molecular branches and the stereochemistry of the monomer on the degradation profile. In another approach, cross-linked films of DXO and CL were prepared using 2,2´-bis-(ε-caprolactone-4-yl) propane (BCP) as the cross-linking agent and Sn(Oct)2 as the catalyst. The networks obtained thereof were elastomeric materials, easy to cast and remove from the mould.

Place, publisher, year, edition, pages
Stockholm: KTH, 2007. 125 p.
Series
Trita-CHE-Report, ISSN 1654-1081 ; 2007:2
Keyword
aliphatic polyester, 1, 5-dioxepan-2-one, ε-caprolactone, L-lactide, D-lactide, D, L-lactide, enzyme, lipase CA, lipase PS
National Category
Polymer Chemistry
Identifiers
urn:nbn:se:kth:diva-4341 (URN)978-91-7178-595-4 (ISBN)
Public defence
2007-05-04, F3, KTH, Lindstedtsvägen 26, Stoclholm, 10:15
Opponent
Supervisors
Note
QC 20100818Available from: 2007-04-20 Created: 2007-04-20 Last updated: 2011-02-21Bibliographically approved

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