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Surface Functionalization of Degradable Polymers by Covalent Grafting
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: 0000-0002-1631-1781
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
2006 (English)In: Biomaterials, ISSN 0142-9612, E-ISSN 1878-5905, Vol. 27, no 9, 1788-1796 p.Article in journal (Refereed) Published
Abstract [en]

With a new non-destructive and solvent-free photografting technique, N-vinylpyrrolidone was covalently grafted onto the surfaces of degradable polymers; poly(L-lactide), poly(L-caprolactone), poly(lactide-co-glycolide),. and poly(trimethylene carbonate). The modified surfaces were characterized by XPS, ATR-FTIR, SEM.. and cell growth tests. The wettability was markedly improved, as static contact angles changed from about 80 degrees for the pristine substrates to around 30 degrees after 30 min of grafting. Well-defined surface topographies, such as micro-patterns, are preserved in the process since the graft layers are thin. The biological response, measured as cytotoxicity, showed that the modified films provide good substrates, comparable with optimized cell culture plastics, for the adhesion and proliferation of normal human keratinocytes and skin fibroblasts.

Place, publisher, year, edition, pages
2006. Vol. 27, no 9, 1788-1796 p.
Keyword [en]
Covalent; Degradable; N-vinyl pyrrolidone; Solvent free; Surface modification; Vapor-phase grafting; Adhesion; Cell culture; Degradation; Substrates; Surface treatment; 1 vinyl 2 pyrrolidinone; carbonic acid derivative; polycaprolactone; polyglactin; polylactide; polymer; polytrimethylene carbonate; solvent; unclassified drug; article; biocompatibility; cell adhesion; cell assay; cell culture; cell growth; cell proliferation; controlled study; covalent bond; cytotoxicity; drug degradation; drug structure; film; human; human cell; infrared spectroscopy; keratinocyte; light; normal human; priority journal; scanning electron microscopy; skin fibroblast; surface property; time; Biocompatible Materials; Biodegradation, Environmental; Cell Adhesion; Cell Proliferation; Cells, Cultured; Dioxanes; Fibroblasts; Humans; Photochemistry; Polyesters; Polyglactin 910; Polymers; Pyrrolidinones; Skin; Surface Properties; Ultraviolet Rays
National Category
Polymer Chemistry
Identifiers
URN: urn:nbn:se:kth:diva-8972DOI: 10.1016/j.biomaterials.2005.10.010ISI: 000234962500014PubMedID: 16257444Scopus ID: 2-s2.0-28744453384OAI: oai:DiVA.org:kth-8972DiVA: diva2:14487
Note
QC 20100804. Uppdaterad från In press till Published 20100804.Available from: 2005-12-28 Created: 2005-12-28 Last updated: 2010-08-04Bibliographically approved
In thesis
1. Covalent Surface Modification of Degradable Polymers for Increased Biocompatibility
Open this publication in new window or tab >>Covalent Surface Modification of Degradable Polymers for Increased Biocompatibility
2005 (English)Licentiate thesis, comprehensive summary (Other scientific)
Alternative title[en]
Nano Patterened Covalent Surface Modification of Poly(ε-caprolactone)
Abstract [en]

Degradable polymers have gained an increased attention in the field of biomedical applications over the past decades, for example in tissue engineering. One way of improving the biocompatibility of these polymers is by chemical surface modification, however the risk of degradation during the modification procedure is a limiting factor. In some biomedical applications, for example in nerve guides, a patterned surface is desired to improve the cell attachment and proliferation.

In this thesis a new non-destructive, single-step, and solvent free method for surface modification of degradable polymers is described. Poly(L-lactide) (PLLA) substrates have been functionalized with one of the following vinyl monomers; N-vinylpyrrolidone (VP), acrylamide (AAm), or maleic anhydride (MAH) grafts. The substrates were subjected to a vapor phase atmosphere constituted of a mixture of a vinyl monomer and a photoinitiator (benzophenone) in a closed chamber at very low pressure and under UV irradiation. Poly(ε-caprolactone) (PCL), poly(lactide-co-glycolide) (PLGA), and poly(trimethylene carbonate) (PTMC) have been surface modified with VP using the same procedure to show the versatility of the method. The wettability of all of the four substrates increased after grafting. The surface compositions were confirmed by ATR-FTIR and XPS. The VP grafted PLLA, PTMC and PLGA substrates have been shown to be good substrates for the normal human cells i.e. keratinocytes and fibroblasts, to adhere and proliferate on. The topography of substrates with well defined nano patterns was preserved during grafting, since the grafted layer is very thin. We have also shown that the method is useful for a simultaneous chemical and topographical modification of substrates by masked vapor phase grafting. The surface topography was determined with SEM and AFM.

Abstract [sv]

Intresset för användningen av nedbrytbara polymerer till biomedicinska applikationer som till exempel vävnads rekonstruktion har ökat avsevärt de senaste decennierna. Ett sätt att öka biokompatibiliteten hos dessa polymerer är genom kemisk ytmodifiering, men risken för nedbrytning under själva modifieringen är en begränsande faktor. I vissa biomedicinska applikationer, till exempel nervguider, är det önskvärt att ha en väldefinierad ytstruktur för att öka vidhäftningen och tillväxten av celler.

I den här avhandlingen presenteras en ny ickeförstörande, lösningsmedelsfri enstegsprocess för ytmodifiering av nedbrytbara polymerer. Substrat av poly(L-laktid) (PLLA) har ytfunktionaliserats med var och en av följande vinylmonomerer, N-vinylpyrrolidon (VP), akrylamid (AAm) eller maleinsyraanhydrid (MAH). Substraten har exponerats för en gasfasatmosfär av en blandning av en vinylmonomer och en fotoinitiator (bensofenon) i en tillsluten reaktor vid mycket lågt tryck och under UV-strålning. Metodens mångsidighet har även påvisats genom att ytmodifiera substrat av poly(ε-kaprolakton) (PCL), poly(laktid-co-glykolid) (PLGA) och poly(trimetylen karbonat) (PTMC) med VP. Vätbarheten ökade för alla fyra materialen efter ympning med en vinylmonomer. Ytsammansättningen fastställdes med ATR-FTIR och XPS. De VP ympade filmerna av PLLA, PLGA och PTMC visade sig vara bra substrat för mänskliga celler, i detta fall keratinocyter och fibroblaster, att vidhäfta och växa på. Yttopografin hos filmer med väldefinierade nanomönstrade ytor kunde bevaras efter ympning, tack vare att det ympade lagret är så tunt. Gasfas metoden har också visat sig användbar för att simultant ytmodifiera både kemiskt och topografiskt genom maskad gasfasympning. Yttopografin bestämdes med SEM och AFM.

Place, publisher, year, edition, pages
Stockholm: KTH, 2005. 59 p.
Series
Trita-FPT-Report, ISSN 1652-2443 ; 2005:37
Keyword
Vapor phase grafting, covalent surface modification, solvent free, nano patterned topography, degradable polymers, poly(ε-caprolactone), poly(L-lactide), poly(lactide-co-glycolide), poly(trimethylene carbonate), N-vinylpyrrolidone, maleic anhydride, acrylamide, Gasfasympning, kovalent ytmodifiering, lösningsmedelsfri, nedbrytbara polymerer, nanomönstrad topografi, poly(L-laktid), poly(ε-kaprolakton), poly(laktid-co-glykolid), poly(trimetylen karbonat), N-vinylpyrrolidon, maleinsyraanhydrid, akrylamid
National Category
Polymer Chemistry
Identifiers
urn:nbn:se:kth:diva-579 (URN)91-7178-195-1 (ISBN)
Presentation
2005-12-09, Salongen, KTHB, Osquars backe 31, Stockholm, 10:00
Opponent
Supervisors
Note
QC 20101014Available from: 2005-12-28 Created: 2005-12-28 Last updated: 2010-12-07Bibliographically approved
2. Covalent Vapor-Phase Grafting of Degradable Polymers
Open this publication in new window or tab >>Covalent Vapor-Phase Grafting of Degradable Polymers
2007 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [sv]

Gasfasympning är en del i den moderna strategin för optimering av den molekylära designen av biomaterial. Kovalent ytmodifiering med hydrofila vinylmonomerer och koppling med bioaktiva grupper används för att öka biokompatibiliteten och bioaktiviteten hos biomaterialen..

I den här avhandlingen presenteras en ny ickeförstörande, enstegsprocess för ytmodifiering av nedbrytbara polymerer. Tekniken är lösningsmedelsfri, utförs vid låga temperaturer och använder lågenergetisk strålning. Substrat exponeras för en gasfasatmosfär bestående av en blandning av fotoinitiator (bensofenon) och vinylmonomer i en försluten reaktor vid mycket lågt tryck och under UV-strålning.

Fyra av de vanligaste nedbrytbara polymera biomaterialen, poly(L-laktid) (PLLA), poly(ε-kaprolakton) (PCL), poly(trimetylenkarbonat) (PTMC) och poly(L-laktid-co-glykolid) (PLGA) har funktionaliserats med N-vinylpyrrolidon (VP). PLLA har ytmodifierats med olika vinylmonomerer, VP, akrylamid (AAm), maleinsyraanhydrid (MAH) och akrylsyra (AA). Den kemiska ytsammansättningen ändrades efter ympningen, och vätbarheten, kvantifierad som statisk kontaktvinkel, ökade kraftigt. Cellodlingsförsök visade att VP-ympad PLLA, PTMC och PLGA är bra material för keratinocyt- och fibroblastceller att fästa vid och växa på. Komplexa strukturer, som t.ex. porösa material med genomgående porer av poly(ε-kaprolakton-co-L-laktid) och poly(1,5-dioxepan-2-one-co-L-laktid) för vävnadsregenerering och sub-mikrometer mönstrad PCL har ytmodifierats med gasfasympning. Yttopografin på dessa materials var välbevarad efter ympning vilket indikerar på att det ympade lagret är mycket tunt. Vätbarheten av de ympade substraten ökade efter ympningen, speciellt för de porösa strukturerna. Hyaluronsyra kopplades kovalent till ett antal porösa filmer för att demonstrera konceptet av att ytterligare öka biokompatibiliteten genom att koppla bioaktiva grupper på de ympade substraten.

En metod för att simultant ytmodifiera nedbrytbara polymerer både kemiskt och topografiskt, maskad gasfasympning, har utvecklats. Analyserna visade sub-mikrometer mönstrade förändringar i den kemiska ytsammansättningen och en ökad vätbarhet.

Gasfasympnings påverkan på nedbrytningshastigheten in vitro har också undersökts. PLLA filmer funktionaliserades med VP, AAm och AA och bröts därefter ned i buffrad salinlösning under varierande tider. Resultaten visade en ändring av nedbrytningshastigheten med avseende på mekaniska egenskaper och viktsminskning. Resultaten visade även att de ympade kedjorna fanns kvar på ytan efter 154 dagars nedbrytning, vilket verifierar att det ympade lagren var kovalent bundna till ytan.

Abstract [en]

Vapor-phase grafting is a step in the modern strategy of optimizing the molecular architecture of biomaterials. Covalent surface modification with hydrophilic vinyl monomers and the coupling of bioactive moieties improves the biocompatibility and bioactivity of the biomaterials.

This thesis describes a new non-destructive, single-step method that has been developed for the surface modification of degradable polymers. The technique is solvent-free, performed at low temperatures, and utilizes low energy irradiation. Substrates are subjected to a vapor-phase atmosphere of photoinitiator (benzophenone) and a vinyl monomer in a closed reactor at very low pressure and low temperature under UV irradiation.

Four of the most commonly used degradable polymeric biomaterials; poly(L-latide) (PLLA), poly(ε-caprolactone) (PCL), poly(trimethylene carbonate) (PTMC), and poly(L-lactide-co-glycolide) PLGA were functionalized with N-vinylpyrrolidone (VP). PLLA was surface modified with different vinyl monomers; VP, acrylamide (AAm), maleic anhydride (MAH), or acrylic acid (AA). The chemical composition of the surface changed upon grafting, and the wettability, assesed by static contact angle measurements, increased markedly. A cell seeding test showed that VP-functionalized PLLA, PTMC, and PLGA substrates are good materials for keratinocyte and fibroblast cells to adhere and proliferate on. Complex structures such as porous scaffolds of poly(ε-caprolactone-co-L-lactide) and poly(1,5-dioxepan-2-one-co-L-Lactide) with interconnected pores, and submicron-patterned PCL were surface modified by vapor-phase grafting. Their topographies were well preserved after grafting, indicating that the grafted layer was very thin. The wettability of the grafted substrates increased after grafting, especially in the case of porous scaffolds. Some porous scaffolds were covalently coupled with hyaluronic acid to demonstrate the concept of coupling bioactive moieties onto the grafted substrates to further improve the biocompatibility.

Masked grafting, a simultaneous chemical and topographical surface modification technique for degradable polymers, was developed. The analyses showed a change in the surface chemistry in sub-micron pattern, and an increase in the wettability.

The influence of vapor-phase grafting with hydrophilic monomers on the in vitro degradation rate has also been investigated. PLLA substrates were functionalized with VP, AAm, and AA and degraded in a buffered saline solution for various time periods. The results showed a change in the degradation rate in terms of mechanical characteristics and weight loss. Grafted monomers remained attached after 154 days of in vitro degradation which confirmed that the grafted layer was covalently attached to the surface.

Place, publisher, year, edition, pages
Stockholm: KTH, 2007. 75 p.
Series
Trita-CHE-Report, ISSN 1654-1081 ; 2007:73
Keyword
Vapor-phase grafting, covalent surface modification, functionalization, solvent-free grafting, sub-micron patterned topography, scaffolds, degradable polymers, poly(L-lactide), poly(ε-caprolactone), poly(trimethylene carbonate), poly(L-lactide-co-glycolide), poly(1, 5-dioxepan-2-one-co-L-lactide), poly(ε-caprolactone-co-L-lactide), N-vinylpyrrolidone, maleic anhydride, acrylamide, acrylic acid, hyaluronic acid, in vitro degradation, Gasfasympning, kovalent ytmodifiering, funktionalisering, lösningsmedelsfri ympning, sub-micrometer mönstrad topografi, nedbrytbara polymerer, poly(L-laktid), poly(ε-kaprolakton), poly(trimetylen karbonat), poly(L-laktid-co-glykolid), poly(1, 5-dioxepan-2-one-co-L-laktid), poly(ε-kaprolakton-co-L-laktid) N-vinylpyrrolidon, maleinsyraanhydrid, akrylamid, akrylsyra, hyaluronsyra, in vitro nedbrytning
National Category
Polymer Chemistry
Identifiers
urn:nbn:se:kth:diva-4544 (URN)978-91-7178-793-4 (ISBN)
Public defence
2007-12-07, K2, Teknikringen 28, Stockholm, 10:00
Opponent
Supervisors
Note
QC 20100804Available from: 2007-11-20 Created: 2007-11-20 Last updated: 2011-10-20Bibliographically approved

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