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Covalent Vapor-Phase Grafting of Degradable Polymers
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
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 [en]
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
Keyword [sv]
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: urn:nbn:se:kth:diva-4544ISBN: 978-91-7178-793-4 (print)OAI: oai:DiVA.org:kth-4544DiVA: diva2:12779
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
List of papers
1. Single-Step Covalent Functionalization of Polylactide Surfaces
Open this publication in new window or tab >>Single-Step Covalent Functionalization of Polylactide Surfaces
2005 (English)In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 127, no 24, 8865-8871 p.Article in journal (Refereed) Published
Abstract [en]

A single-step, nondestructive, and versatile technique for the grafting and chemical surface modification of biodegradable polymers such as polylacticle is described. The substrates are subjected to the vapor phase of any of three investigated vinyl monomers: acrylamide, maleic anhydride, and N-vinylpyrrolidone, and grafting is induced by photoinitiation of benzophenone under solvent free conditions. The modified surfaces exhibit higher wettability, and the grafting is verified by X-ray photoelectron spectroscopy, attenuated total reflection Fourier-transform IR, contact-angle measurements, and scanning electron microscopy. The graft-chain pendant groups remain functional and can subsequently be modified so that a tailor-made surface with desired properties may be achieved.

Keyword
Biodegradation; Chemical modification; Contact angle; Fourier transform infrared spectroscopy; Grafting (chemical); Monomers; Scanning electron microscopy; Substrates; Surface treatment; X ray photoelectron spectroscopy; Biodegradable polymers; Polylactide; Vapor phase; Vinyl monomers; Acrylamide; Benzophenones; Gases; Maleic Anhydrides; Photochemistry; Polyesters; Pyrrolidinones; Spectroscopy, Fourier Transform Infrared; Surface Properties; Ultraviolet Rays
National Category
Polymer Chemistry
Identifiers
urn:nbn:se:kth:diva-8971 (URN)10.1021/ja052073u (DOI)000229981200047 ()15954795 (PubMedID)2-s2.0-20944443598 (Scopus ID)
Note
QC 20100804Available from: 2005-12-28 Created: 2005-12-28 Last updated: 2017-12-14Bibliographically approved
2. Surface Functionalization of Degradable Polymers by Covalent Grafting
Open this publication in new window or tab >>Surface Functionalization of Degradable Polymers by Covalent Grafting
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.

Keyword
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:nbn:se:kth:diva-8972 (URN)10.1016/j.biomaterials.2005.10.010 (DOI)000234962500014 ()16257444 (PubMedID)2-s2.0-28744453384 (Scopus ID)
Note
QC 20100804. Uppdaterad från In press till Published 20100804.Available from: 2005-12-28 Created: 2005-12-28 Last updated: 2017-12-14Bibliographically approved
3. Nano Patterened Covalent Surface Modification of Poly(ε-caprolactone)
Open this publication in new window or tab >>Nano Patterened Covalent Surface Modification of Poly(ε-caprolactone)
2005 (English)In: Israel Journal of Chemistry, ISSN 0021-2148, Vol. 45, no 4, 429-435 p.Article in journal (Refereed) Published
Abstract [en]

Using our new vapor-phase grafting technique, we have simultaneously chemically and physically modified the surface of poly(e-caprolactone) (PCL) films. The substrates were covered with nano patterned silicone rubber stamps and subjected to UV irradiation in the presence of the solvent-free vapor phase of either N-vinyl pyrrolidone or maleic anhydride, and a photoinitiator, under reduced pressure. The treated films display a surface pattern of grafted channels of 450-nm width, as confirmed by AFM and SEM. The grafting was further verified with ATR-FTIR, and contact angle measurements show an increased wettability of the surfaces.

Keyword
POLYMER SURFACES, BIOMATERIALS, CELLS; FILM, FUNCTIONALIZATION, OXYGEN, LLDPE
National Category
Polymer Chemistry
Identifiers
urn:nbn:se:kth:diva-8973 (URN)10.1560/BY1J-CGHN-7MF4-QX85 (DOI)000233570300006 ()2-s2.0-27844477377 (Scopus ID)
Note
QC 20101207Available from: 2005-12-28 Created: 2005-12-28 Last updated: 2017-12-14Bibliographically approved
4. Covalent Grafting of Poly(L-lactide) to Tune the In Vitro Degradation Rate
Open this publication in new window or tab >>Covalent Grafting of Poly(L-lactide) to Tune the In Vitro Degradation Rate
2007 (English)In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 8, no 8, 2492-2496 p.Article in journal (Refereed) Published
Abstract [en]

The in vitro rate of degradation was purposely affected by covalently grafting the surface of poly(L-lactide) (PLLA). PLLA films were surface modified by our vapor-phase nondestructive photografting technique. Films were grafted for 20 min with one of the following monomers: acryl amide (AAm), N-vinyl pyrrolidone (VP), or acrylic acid (AA) and thereafter incubated in vitro in a phosphate-buffered saline solution at 37 C for 154 days. The films were studied with contact angle measurements, SEM, ATR-FTIR, SEC, and DSC. The analyses verified that the in vitro rate of degradation was enhanced and that the grafted surface layer did remain covalently attached to the surface during the initial stages of incubation.

Keyword
Contact angle; Degradation; Differential scanning calorimetry; Fourier transform infrared spectroscopy; Grafting (chemical); Scanning electron microscopy; Surface treatment; Covalent grafting; Degradation rate; In vitro degradation; Polylactide; Biopolymers; 1 vinyl 2 pyrrolidinone; acrylamide; acrylic acid; phosphate buffered saline; polylactide; article; Fourier transform mass spectrometry; gel permeation chromatography; in vitro study; photodegradation; priority journal; protein degradation; scanning electron microscopy; temperature dependence; Acrylamide; Acrylates; Calorimetry, Differential Scanning; Microscopy, Electron, Scanning; Phosphates; Polyesters; Pyrrolidinones; Spectroscopy, Fourier Transform Infrared; Surface Properties
National Category
Polymer Chemistry
Identifiers
urn:nbn:se:kth:diva-7679 (URN)10.1021/bm700442j (DOI)000248755000021 ()17630795 (PubMedID)2-s2.0-34548275104 (Scopus ID)
Note
QC 20100804Available from: 2007-11-20 Created: 2007-11-20 Last updated: 2017-12-14Bibliographically approved
5. Surface Functionalization of Porous Resorbable Scaffolds by Covalent Grafting
Open this publication in new window or tab >>Surface Functionalization of Porous Resorbable Scaffolds by Covalent Grafting
2008 (English)In: Biomaterials, ISSN 0142-9612, E-ISSN 1878-5905, Vol. 8, no 7, 645-654 p.Article in journal (Refereed) Published
Abstract [en]

Resorbable porous scaffold discs and solid films were prepared from poly[(1,5-dioxepan-2one)-co-(L-lactide)] and poly [(epsilon-caprolactone)-co-(L-lactide)]. The surfaces of the scaffolds were functionalized to increase their hydrophilicity. A total of 90 samples were prepared to cover all important combinations of experimental and material factors, and all experimental data were fitted by a partial least square model. As a result of grafting, the porous discs and solid films exhibited a tremendous increase in wettability. The functionalized discs were hygroscopic so that water was instantly absorbed and thoroughly wet the substrates.

Keyword
Biocompatibility; Functionalization of polymers; Grafting; Scaffolds; Surface modification; ABS resins; Biocompatibility; Curve fitting; Film preparation; Functional polymers; Grafting (chemical); Ketones; Surfaces; Caprolactone; Covalent grafting; Experimental datum; Functionalization of polymers; Functionalized; Grafting; Lactide; Material factors; Partial least square models; Porous scaffolds; Solid films; Surface functionalization; Surface modification; 1, 5 benzodioxepane derivative; molecular scaffold; polycaprolactone; polylactide; lactide caprolactone copolymer; lactide-caprolactone copolymer; polyester; water; article; chemical binding; controlled study; covalent grafting; hydrophilicity; partial least squares regression; porosity; surface property; water absorption; wettability; absorption; chemistry; hydrophobicity; Absorption; Hydrophobicity; Polyesters; Porosity; Water; Wettability
National Category
Polymer Chemistry
Identifiers
urn:nbn:se:kth:diva-7680 (URN)10.1002/mabi.200700329 (DOI)000257817300006 ()18383572 (PubMedID)2-s2.0-54049136569 (Scopus ID)
Note
QC 20100804. Uppdaterad från Submitted till Published 20100804.Available from: 2007-11-20 Created: 2007-11-20 Last updated: 2017-12-14Bibliographically approved

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