Biomedical subjects

Juergen Groll

Publications and source records attributed to Juergen Groll.

5 recordsLinked to original sources

PubMed2005

A novel star PEG-derived surface coating for specific cell adhesion.

In this study a novel approach for the coating and functionalization of substrates for cell culture and tissue engineering is presented. Glass, silicon, and titanium panes were coated with an ultrathin film (30 +/- 5 nm) of reactive star-shaped poly(ethylene glycol) prepolymers (Star PEG). Homogeneity of the films was checked by optical microscopy and scanning force microscopy. These coatings prevent unspecific protein adsorption as monitored by fluorescence microscopy and ellipsometry. In order to allow specific cell adhesion the films were modified with linear RGD peptides (gRGDsc) in different concentrations. After sterilization, fibroblast, SaOS, and human mesenchymal stem cells (hMSC) were seeded on these substrates. Cell adhesion, spreading, and survival was observed for up to 30 days on linear RGD peptide (gRGDsc)-modified coatings, whereas no cell adhesion could be detected on unmodified Star PEG layers. By variation of the RGD concentration within the film the amount of cells that became adhesive could be controlled. When differentiation conditions are used for cultivation of hMSCs the cells show the expression of osteogenic marker genes after 14 days which is comparable to cultivation on cell culture plastic. Thus, the Star PEG/RGD film did not negatively influence the differentiation process. The high flexibility of the system considering the incorporation of biologically active compounds opens a broad field of future experiments.

Adult↗

PubMed2005

Ultrathin coatings from isocyanate terminated star PEG prepolymers: patterning of proteins on the layers.

This study presents the easy and fast patterning of low molecular weight molecules that act as binding partners for proteins on Star PEG coatings. These coatings are prepared from isocyanate terminated star shaped prepolymers and form a highly cross-linked network on the substrate in which the stars are connected via urea groups and free amino groups are present. Streptavidin has been patterned on these layers by microcontact printing (muCP) of an amino reactive biotin derivative and consecutive binding of streptavidin to the biotin. Patterns of Ni(2+)-nitriltriacetic acid (NTA) receptors have been prepared by printing amino functional NTA molecules in freshly prepared Star PEG layers that still contain amino reactive isocyanate groups. Complexation of the NTA groups with Ni(II) ions enabled the binding of His-tag enhanced green fluorescent protein (EGFP) in the desired pattern on the substrates. Since the unmodified Star PEG layers prevent unspecific protein adsorption, His-EGFP could selectively be bound to the sample by immersion into crude, nonpurified His-tag EGFP containing cell lysate.

Biotin↗

PubMed2005

Ultrathin coatings from isocyanate-terminated star PEG prepolymers: layer formation and characterization.

In this study we present the preparation of thin and ultrathin coatings from six-arm star-shaped isocyanate-terminated prepolymers on amino-functionalized silicon wafers. The backbone of the stars is a statistical copolymer of ethylene oxide and propylene oxide in the ratio 80:20 (Star PEG). Film preparation by spin coating from aqueous THF resulted in a variety of film morphologies that are determined by the water content of the solvent. Water is indispensable for activation of the isocyanate-terminated stars in solution and for proper cross-linking of the coatings on the substrate. This cross-linking results in a dense network of PEG chains on the substrate linked via urea groups with a mesh size of the network that corresponds to the arm length of the stars. Layer thickness variations between 3 and 500 nm revealed a strong dependence of the contact angle with water on the layer thickness which is explained by the chemical composition of the coatings. Due to the high functionality of the star-shaped prepolymers, free amino groups remain in the films that were detected by fluorescence microscopy after reaction with 4-chloro-7-nitrobenzofurazan (NBF). To test the system for the ability to prevent unspecific interaction with proteins, adsorption of fluorescence-labeled avidin was examined with fluorescence microscopy. For layer thicknesses between 3 and 50 nm, no protein adsorption could be detected.

Journal Article↗

PubMed2005

Nanostructured ordering of fluorescent markers and single proteins on substrates.

Highly ordered hexagonal nanopatterns of gold clusters on glass substrates were used as anchoring points for the specific attachment of fluorescence dyes and proteins labeled with fluorescence dyes. Thiol- or disulfide-containing linker molecules were used for the binding to the gold dots. In order to ensure specific binding on the gold dots only, the surface area in between the dots was protected against unspecific adsorption. For the attachment of polar low-molecular-weight fluorescence dyes, an octadecyltrichlorosilane self-assembled monolayer was prepared on the surface in between the gold dots, whereas a layer prepared from star-shaped poly(ethylene oxide-stat-propylene oxide) prepolymers was used to prevent unspecific adsorption of proteins between the gold dots. Fluorescence microscopy proved the specific binding of the dyes as well as of the proteins. Scanning force microscopy studies show that each gold dot is only capable of binding one protein at a time.

Avidin↗

PubMedDate not supplied

Ultrathin functional star PEG coatings for DNA microarrays.

In this study, star PEG coatings on glass substrates have been used as support material for oligonucleotide microarrays. These coatings are prepared from solutions of six armed star shaped prepolymers that carry reactive isocyanate endgroups. As described earlier, such films prevent the adsorption of proteins and the adhesion of cells but can easily be functionalized for specific biological recognition. Here we used the high functionality of these coatings for the covalent immobilization of amino terminated 20mer oligonucleotides, both by microcontact printing and spotting techniques. The permanent immobilization of fluorescently labeled DNA as well as hybridization of 20mer oligonucleotides have been monitored by fluorescence microscopy. The hybridization efficiency as determined by fluorescence intensity varied from 30% to 80% depending on the way of layer preparation. The direct spotting without additional activation and blocking steps of the surface demonstrates the potential of star PEG coatings as ultrathin surface modification for microarrays.

Base Sequence↗