Roland Wacker

Enhanced Biocompatibility for SAOS-2 Osteosarcoma Cells by Surface Coating with Hydrophobic Epoxy Resins

Background and Aims: Implants for surgical needs are produced from different materials including metals, alloys, ceramics or polymers. Metal implants are preferred in those disciplines where sufficient mechanical strength is needed, including traumatology, orthopedic or dental surgery. Further, modern tissue engineering techniques require scaffold materials to generate shape and stability for in vitro generated transplants. However, the biocompatibility and surface contact of most implants or scaffold materials to vital bone or other tissues are not optimal. Therefore we investigated the biocompatibility of different polymer surfaces to an osteoblastic cell line as a function of wettability or hydrophobicity to describe some of the surface parameters influencing the cell to implant or cell to scaffold contact. Methods: Glass slides were coated with different polymers and in some cases physically or chemically modified. SAOS-2 osteosarcoma cells were used for the biocompatibility tests on 16 different polymers and modifications thereof. The viability of the adherent cells was investigated by MTT assay. Commercially available tissue culture vessels served as controls. Results: We report that excellent biocompatibility to SAOS-2 osteoblastic cells can be obtained with hydrophobic surfaces generated for instance by epoxy resins. Chemical modification of epoxy resin surfaces yielded even a further increased viability index surpassing the viability index obtained with cell culture vessels. Conclusion: We conclude that modified hydrophobic surfaces represent an interesting group of compounds for coating endoprosthetic implants or scaffolds for the purposes of tissue engineering.

Mistletoe lectin I in complex with galactose and lactose reveals distinct sugar-binding properties

The structures of mistletoe lectin I (ML-I) from Viscum album complexed with lactose and galactose have been determined at 2.3 A resolution and refined to R factors of 20.9% (Rfree = 23.6%) and 20.9 (Rfree = 24.6%), respectively. ML-I is a heterodimer and belongs to the class of ribosome-inactivating proteins of type II, which consist of two chains. The A-chain has rRNA N-glycosidase activity and irreversibly inhibits eukaryotic ribosomes. The B-chain is a lectin and preferentially binds to galactose-terminated glycolipids and glycoproteins on cell membranes. Saccharide binding is performed by two binding sites in subdomains alpha1 and gamma2 of the ML-I B-chain separated by approximately 62 A from each other. The favoured binding of galactose in subdomain alpha1 is achieved via hydrogen bonds connecting the 4-hydroxyl and 3-hydroxyl groups of the sugar moiety with the side chains of Asp23B, Gln36B and Lys41B and the main chain of 26B. The aromatic ring of Trp38B on top of the preferred binding pocket supports van der Waals packing of the apolar face of galactose and stabilizes the sugar-lectin complex. In the galactose-binding site II of subdomain gamma2, Tyr249B provides the hydrophobic stacking and the side chains of Asp235B, Gln238B and Asn256B are hydrogen-bonding partners for galactose. In the case of the galactose-binding site I, the 2-hydroxyl group also stabilizes the sugar-protein complex, an interaction thus far rarely detected in galactose-specific lectins. Finally, a potential third low-affinity galactose-binding site in subunit beta1 was identified in the present ML-I structures, in which a glycerol molecule from the cryoprotectant buffer has bound, mimicking the sugar compound.

Biocompatibility correlation of polymeric materials using human osteosarcoma cells

Abstract Metal implants are the preferred materials to generate articular prostheses, plates, or bone pegs in orthopedic surgery. Although titanium and titanium alloys show a relatively good biocompatibility, clinical experience revealed that coating of the metallic implant surface may increase the biocompatibility. In a search for optimum bone implant surfaces, we determined polarity and contact angle parameters of a variety of polymers and substances and correlated the findings in a biocompatibility assay using an in vitro bone cell model. We report that an optimum adherence of SAOS-2 cells to such surfaces and a good vitality for polymers are characterized by water-based contact angles of 80° and 20° for advancing and receding probes, respectively.

Polymer-gestützte Synthese von Biopolymeren —Grundlagen und Anwendungen

The application of polymer supports for the synthesis of polypeptides, oligonucleotides, and oligosaccharides is presented in this article and discussed in view of their methodology. The fundamentals of the polymer-supported synthesis are described as well as the role of the polymer supports in the synthetic cycle, and the problems associated are debated. It is focused on typical polymer supports for each substance class, and an overview is given on recent tendencies of development in the polymer-supported methods of synthesis.