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Covalent Grafting of Poly(L-lactide) to Tune the In Vitro Degradation Rate
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.
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.

Place, publisher, year, edition, pages
2007. Vol. 8, no 8, 2492-2496 p.
Keyword [en]
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: urn:nbn:se:kth:diva-7679DOI: 10.1021/bm700442jISI: 000248755000021PubMedID: 17630795Scopus ID: 2-s2.0-34548275104OAI: oai:DiVA.org:kth-7679DiVA: diva2:12777
Note
QC 20100804Available from: 2007-11-20 Created: 2007-11-20 Last updated: 2017-12-14Bibliographically approved
In thesis
1. 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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