Publikationsserver der RWTH Aachen University
Verfahren zur Funktionalisierung und bioaktiven Ausrüstung von Implantatoberflächen für eine verbesserte Gewebeintegration
Abstract
dc:descriptionGeneration of aliphatic amino groups by means of CVD-coating Within the course of this work a novel CVD-coating, which allows the generation of aliphatic amino functional groups on the surface of various materials, was developed. In particular a high availability of functional groups as anchor groups for immobilisation reactions was intended. As novel starting material for the CVD-process 4-aminomethyl-[2.2]-paracyclophane was synthesised from 4-hydroxymethyl-[2.2]-paracyclophane in three high yielding steps. The respective products were identified by means of NMR, IR and MALDI-TOF-MS. The CVD-procedure led to an insoluble, transparent polymer film with good adhesion to different substrates. AFM-analyses showed a high homogeneity of the coating. XPS- and IR/ATR-investigations respectively proved the element composition and functionality corresponding to poly(aminomethyl-p-xylylene-co-p-xylylene) (AM-ppx). Zetapotential measurements confirmed the aliphatic character of the amino groups. Their suitability as anchor groups was investigated by means of an immobilisation/cleavage sequence: The subsequent acid induced release of dimethoxytrityl cations from dimethoxytrityl derivatives, which were immobilised by means of two typical coupling reactions, was quantified. A significant better availability of the aliphatic amino groups of AM-ppx in comparison to the aromatic amino groups of the analogous CVD-coating poly(amino-p-xylylene-co-p-xylylene) (amino-ppx) was verified. Bioactive outfitting of CVD-coated surfaces The methods of bioactive outfitting, as developed here, were aimed at the long-term tissue-compatibility of implants. Based on the CVD-coating amino-ppx the covalent immobilisation of insulin and the peptide GRGDS was intended to promote the proliferation and adhesion of cells on the surface. Coupling of the bioactive substances was performed directly onto the CVD-coating as well as onto an additional hydrophilic layer of carboxymethyldextran (CM-dextran). The hydrogel was used to achieve a low protein adsorption in vivo and hence a free access to the immobilised molecules. CM-dextran was obtained by the treatment of dextran with bromoacetic acid. Via NMR carboxymethylation was mainly found in Alpha-position to the acetal groups of the glucan. The immobilisation of CM-dextran by hexamethylene diisocyanate was verified by means of contact angle measurements and XPS. The thickness of the swollen hydrogel layer was determined via AFM. Besides a non-selective coupling a selective immobilisation of insulin was performed via previously synthesised A1,B29-Msc2-insulin. The protected insulin was identified by means of MALDI-TOF-MS after oxidative-sulfitolytic and tryptic fragmentation respectively. For covalent immobilisation activated amino-ppx- and CM-dextran-surfaces were treated with aqueous solutions of insulin and peptide. Immobilised amounts were analysed via radiolabelling and ELISA (insulin). Covalent immobilisation onto amino-ppx was proven by surface-MALDI-TOF-MS. Radiolabelling and ELISA experiments with fibrinogen indicated a very low protein adsorption on CM-dextran-modified surfaces. In vitro cell tests were performed using human umbilical vein endothelial cells (HUVEC). After 48 h a high density of adhering cells was found only on amino-ppx surfaces with covalently bound insulin and on CM-dextran surfaces with covalently bound GRGDS. Bioactive outfitting of platinum surfaces by thiols Taking advantage of its thiophilic character a single-step approach for the bioactive modification of platinum was pursued. Following a known procedure for gold the previously synthesised thiols (1-mercaptoundec-11-yl)-triethylene glycol (EG3-thiol) as protein-rejecting component und N-(32-mercapto-1-oxo-3,6,9,12,15,18,21-heptaoxadotriacontyl)-GRGD (EG6-GRGD-thiol) as cell-binding component were used. Cleaned platinum foils were treated with thiol-solutions in ethanol. Covalent thiol-immobilisation was verified via XPS. The estimated SAM thickness as well as the measured contact angle was corresponding with the literary values for gold/thiol. As indicated via ELISA the thiol treatment of platinum led to a strong reduction of the fibrinogen adsorption. The modified platinum samples were incubated with fetal rat fibroblasts for 48 h. Strongly adhering cells were only found on surfaces treated with EG6-GRGD-thiol containing solutions.
Degree
thesis:*- Grantor dc:publisher
- Publikationsserver der RWTH Aachen University
- Year dc:date
- 2004
Author and committee
dc:creator, dc:contributor.*- Author dc:creator
-
- Weiß, Norbert
- Contributors dc:contributor
-
- Höcker, Hartwig
Subjects
dc:subject × 8Rights
dc:rights- Statement dc:rights
-
- info:eu-repo/semantics/openAccess
- Language dc:language
- ger