Funktionalisierung von Polydimethylsiloxan-Oberflächen zur Steuerung molekularer Zell-Substrat Wechselwirkungen

Aim of this work is the formation of biologically functional PDMS surfaces which are able to control adhesion and proliferation of cells like fibroblasts and keratinocytes. This purpose requires biologically inert hydrogel layers on PDMS that prevent unspecific protein adsorption and - as a consequence - cell adhesion. Hydrogels were covalently bound to amino groups, produced in the PDMS surface. Peptide sequences or aptamers were reacted with the hydrogel layer to allow specific cell adhesion via ligand-receptor interactions. First PDMS surfaces were functionalised with amino groups. Exposition in ammonia-plasma leads to higher surface hydrophilicity compared to the untreated material. Measurement of the zeta-potential and derivatisation reactions showed the presence and accessibility of primary amine groups, additional surface crosslinking was observed. However, the functionalisation with amino groups was not stable over several days of storage. The influence of plasma treatment with ammonia-argon mixtures, argon plasma supported graft-co-polymerisation of allylamine and CVD-polymerisation of amino functionalized paracyclophane were also investigated. Lateral structuring of the surface functionalisation was achieved with mask techniques on a 10 µm scale. In a second step hydrogels were bound to PDMS surfaces which were functionalized in ammonia plasma. Carboxymethylated dextran (CM-dextran), maleimid functionalised dextran (MI-dextran) and a six-arm isocyanate functionalised star shaped polyether (80% ethylene oxide and 20% propylene oxide) (starPEG) were used. Modification with dextran or starPEG showed distinct improvement of the wettability with water. Surface tension and zeta-potential indicated beside surface hydrophilicity readily accessible amino endgroups of the starPEG. The dextran- as well as the starPEG-coating were able to reduce the protein adsorption. This was proved by the use of surface-MALDI-ToF-MS and studies with the streptavidin-rhodamin-conjugate. Adsorption of insulin, lysozym and albumin were prohibited, after treatment with human blood plasma no albumin, transferrin, transthyretin and no lipoproteins apo C-I and apo C-II could be detected. PDMS surfaces modified with starPEG showed no adhesion and proliferation of human HaCaT keratinocytes and SaOs-2 osteoblasts over 21 days. Only a few fetal rat fibroblasts adhered on surfaces modified with either starPEG or CM-dextran, compared to cells on untreated surfaces which were vital and thus documented the in vitro biocompatibility of the modifications. Mixtures of starPEG and CM-dextran showed as well good protein- and cell-repellent properties. In a third step biological ligands were grafted onto PDMS foils modified with CM-dextran, MI-dextran or starPEG. Covalently immobilised peptides with the RGD-sequence resulted in enhanced adhesion and proliferation of fibroblasts. The concentration of the peptide regulated the density of adherent cells. Adhesion of keratinocytes on surfaces modified with starPEG- or CM-dextran and bound peptide sequences from fibronectin (GRGDS and PHSRN), laminin (YIGSR) or collagen IV (GEFYFDLRLKGDK) or rather mixtures of these peptides was found to be strong, partially the cells formed confluent epithelial aggregates. Combination of GRGDS with GEFYFDLRLKGDK lead to the strongest positive influence on adhesion and proliferation of keratinocytes on all investigated modified surfaces with single peptide sequences or mixtures of two or more peptides. With the microcontact printing technique even small peptide sequences were immobilized in lateral structures, so fibroblasts had the possibility to adhere and to form focal contacts at well-defined sites. Studies of the influence of mechanical stimulation of fibroblasts during their adhesion on PDMS showed, that more cells adhered better spread and distributed than without mechanical stimulation. A lot of cells aligned orthogonally to the stress direction and had a flattened morphology. Modification of PDMS for a targeted attachment of haematopoietic precursor cells was achieved through immobilisation of specifically selected aptamers onto PDMS-surfaces modified with CM-dextran or starPEG. Investigations of the endothelialisation behaviour of human as well as porcine endothelial precursor cells (EPCs) from the whole blood showed that the modified surfaces are able to selectively bind EPCs and hence to promote a specific endothelialisation of the synthetic material surfaces.

Grantor dc:publisher

Publikationsserver der RWTH Aachen University

Year dc:date

2007

Author dc:creator

• Harwardt, Marc Michael

Contributors dc:contributor

• Höcker, Hartwig

• info:eu-repo/classification/ddc/540
• Oberflächenveredelung
• Biomaterial
• Mikrowellenplasma
• CVD-Verfahren
• Hydrogel
• Polyethylenglykole
• Peptide
• Aptamer
• Strukturierung
• Integrine
• Polydimethylsiloxane
• Chemie
• RGD
• Dextran
• mechanische Stimulierung
• Biokompatibilität
• Keratinozyten
• micro contact printing
• surface
• hydrogels
• plasma

Statement dc:rights

• info:eu-repo/semantics/openAccess

Language dc:language

ger

Identifier

https://publications.rwth-aachen.de/search?p=id:%22RWTH-CONV-124050%22

OAI identifier oai:identifier

oai:publications.rwth-aachen.de:62484