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Adjustable Degradation Properties and Biocompatibility of Amorphous and Functional Poly(ester-acrylate)-Based Materials
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.ORCID iD: 0000-0001-6044-586X
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.ORCID iD: 0000-0002-1922-128X
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
2014 (English)In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 15, no 7, 2800-2807 p.Article in journal (Refereed) Published
Abstract [en]

Tuning the properties of materials toward a special application is crucial in the area of tissue engineering. The design of materials with predetermined degradation rates and controlled release of degradation products is therefore vital. Providing a material with various functional groups is one of the best ways to address this issue because alterations and modifications of the polymer backbone can be performed easily. Two different 2-methylene-1,3-dioxepane/glycidyl methacrylate-based (MDO/GMA) copolymers were synthesized with different feed ratios and immersed into a phosphate buffer solution at pH 7.4 and in deionized water at 37 degrees C for up to 133 days. After different time intervals, the molecular weight changes, mass loss, pH, and degradation products were determined. By increasing the amount of GMA functional groups in the material, the degradation rate and the amount of acidic degradation products released from the material were decreased. As a result, the composition of the copolymers greatly affected the degradation rate. A rapid release of acidic degradation products during the degradation process could be an important issue for biomedical applications because it might affect the biocompatibility of the material. The cytotoxicity of the materials was evaluated using a MTT assay. These tests indicated that none of the materials demonstrated any obvious cytotoxicity, and the materials could therefore be considered biocompatible.

Place, publisher, year, edition, pages
2014. Vol. 15, no 7, 2800-2807 p.
Keyword [en]
degradation, biocompatible, functional, aliphatic polyesters, cyclic ketene acetal, 2-methylene-1, 3-dioxepane, radical ring-opening polymerization, MTT assay
National Category
Polymer Technologies
Research subject
Fibre and Polymer Science
URN: urn:nbn:se:kth:diva-145186DOI: 10.1021/bm500689gISI: 000339090500051ScopusID: 2-s2.0-84904295082OAI: diva2:717124
EU, European Research Council, 246776

QC 20140819. Updated from submitted to published.

Available from: 2014-05-14 Created: 2014-05-14 Last updated: 2014-08-19Bibliographically approved
In thesis
1. Functional Degradable Polymers by a Radical Chemistry approach
Open this publication in new window or tab >>Functional Degradable Polymers by a Radical Chemistry approach
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

One class of polymers that is inherently of great value for many applications is the aliphatic polyesters. Such polymers are very suitable for use as temporary guides, scaffolds, for tissue formation and other biomedical applications, due to their biocompatibility, degradability and appropriate mechanical properties. A prominent way to incorporate sites that allow alterations and modifications of the polymer backbone could be by copolymerization of functional monomers. The focus in this thesis is the development of new monomers and subsequent polymers bestowed with functional groups.

Radical ring-opening polymerization (RROP) of cyclic ketene acetals through a free-radical mechanism presents an alternative route to conventional ring-opening polymerization for the synthesis of aliphatic polyesters. By RROP, it is possible to incorporate ester functionality into the backbone of non-degradable polymers by copolymerize cyclic ketene acetals with vinyl monomers.

The possibility of creating materials with high degree of functionality is achieved by copolymerization with other and possible functional monomers. Three different copolymerizations including cyclic ketene acetals were performed. First, to increase hydrophilicity of a hydrophobic polymer by copolymerization of two cyclic ketene acetals, 2-methylene-1,3,6-trioxocane (MTC) and 2-methylene-1,3-dioxepane (MDO). Second, to introduce degradability into a non-degradable backbone by copolymerize MDO and vinyl acetal (VAc). Subsequently, the acetate side-group was hydrolyzed into the more hydrophilic alcohol group. Third, to introduce reactive functionalities into the degradable backbone of poly(2-methylene-1,3-dioxepane) (PMDO), by copolymerize MDO and glycidyl methacrylate (GMA). The epoxide side-groups, originating from GMA, were subsequently used in post-polymerization reactions by coupling with the bioactive molecule heparin.

The degradability of this class of copolymers was evaluated using the MDO/GMA-based material as model, showing that the materials degrade during 133 days without a rapid release of acidic degradation products or any substantial lowering of the pH. Methylthiazol tetrazolium (MTT) assays were also performed to confirm the innocuousness of the material. The results from the degradation study together with the MTT assays showed that these materials would be interesting for use in biomedical applications.

Finally, a combination of controlled radical polymerization with controlled ring-opening polymerization was performed. α-Bromo-γ-butyrolactone (αBrγBL) together with ε-caprolactone (εCL) or L-lactide (LLA) was successfully copolymerized to achieve copolymers with active and available grafting sites for single electron transfer living radical polymerization (SET-LRP). Different acrylates, ranging from the hydrophobic n-butyl acrylate and methyl methacrylate to the hydrophilic 2-hydroxyethyl methacrylate, were subsequently grafted via SET-LRP. All designated acrylate monomers were successfully grafted onto the polymer backbone, thereby emphasizing the versatility and ability of αBrγBL to act as a bridge between SET-LRP and ROP for a wide range of monomers.

Abstract [sv]

De alifatiska polyestrarna är en klass polymerer som är av stort intresse för många applikationer. Dessa polymerer är mycket lämpade att använda som temporära guider, scaffolds, för vävnadsregenerering och andra biomedicinska applikationer, på grund av sin biokompatibilitet, nedbrytbarhet och goda mekaniska egenskaper. Ett bra sätt att introducera funktionella grupper, som tillåter ändringar och modifikationer i polymerkedjan, kan vara att sampolymerisera med funktionella monomerer. I denna avhandling har därför fokus varit på att utveckla nya funktionella monomerer och polymerer.

Radikal ringöppningspolymerisation (RROP) av cykliska ketenacetaler har visat sig vara ett bra alternativ till att syntetisera alifatiska polyestrar jämfört med vanlig traditionell ringöppningspolymerisation. Med RROP är det möjligt att inkorporera esterfunktionalitet i polymerkedjan för icke nedbrytbara polymerer genom att sampolymerisera cykliska ketenacetaler med vinylmonomerer.

Möjligheten att skapa material med hög grad av funktionalitet uppnås genom att sampolymerisera med andra funktionella monomerer. Tre olika sampolymerer syntetiserades. Den första sampolymeren tillverkades för att introducera hydrofilicitet till en hydrofob polymer genom att sampolymerisera två ketenacetaler; 2-metyl-1,3,6-trioxocan (MTC) och 2-metyl-dioxepan (MDO). Därefter sampolymeriserades MDO med vinylacetat (VAc) för att tillföra nedbrytbarhet från MDO till ett, från huvudkedjan, onedbrytbart material. Acetatgruppen hydrolyserades därefter till den mer hydrofila alkoholgruppen. Som en sista sampolymerisation gjordes en med MDO med glycidylmetakrylat (GMA) för att införa funktionalitet till en nedbrytbar polymer. Epoxidgruppen tillhörande GMA, användes därefter för att kovalent koppla på den bioaktiva molekylen heparin på sampolymeren.

Nedbrytbarheten i denna klass av sampolymerer undersöktes med hjälp av att använda det MDO/GMA-baserade materialet som modell. Som resultat visade det sig att man, efter 133 dagar, varken kunde se en snabb frisättning av sura nedbrytningsprodukter eller en stor sänkning av pH. MTT-analyser utfördes för att visa att materialet inte var giftigt. Både resultaten från nedbrytningsstudien tillsammans med MTT-analyserna visade att dessa material är potentiella material för användning i biomedicinska applikationer.

Till sist kombinerades kontrollerad radikalpolymerisation med kontrollerad ringöppningspolymerisation. För att syntetisera funktionella makroinitiatorer sampolymeriserades monomeren α-brom-γ-butyrolakton (αBrγBL) med ε-kaprolakton (εCL) eller L-laktid (LLA). Dessa makroinitiatorer har aktiva grupper längs med huvudkedjan som kan användas för ympning av olika akrylater; från de hydrofoba n-butylakrylat och metylmetakrylat till den hydrofila 2-hydroxyetylmetakrylat med hjälp av en kontrollerad radikalpolymerisationsmetod som kallas för SET-LRP. Genom att lyckas ympa ett brett spektrum av monomer med olika egenskaper på polyester-makroinitiatorerna resulterade detta i att det gick att kombinera två olika polymerisationsmetoder på ett enkelt sätt.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2014. 74 p.
TRITA-CHE-Report, ISSN 1654-1081 ; 2014:22
National Category
Polymer Technologies
Research subject
Fibre and Polymer Science
urn:nbn:se:kth:diva-145193 (URN)978-91-7595-126-3 (ISBN)
Public defence
2014-05-23, K2, Teknikringen 28, KTH, Stockholm, 10:00 (English)

QC 20140514

Available from: 2014-05-14 Created: 2014-05-14 Last updated: 2014-05-14Bibliographically approved

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