Surface modification for direct immunoprobes

The modification of glass-type surfaces by several hydrophilic polymers of different molecular masses and functional properties [chitosan, dextran, poly(oxyethylene), poly(ethyleneimine) and poply(acrylamide)] with respect to the application for direct immunoprobes was investigated. Activation of the surface was carried out by silanisation and the polymers were coupled to the surface via amide bonds. The carboxyl derivative of a hapten was attached to the functional groups of the polymers by carbodiimide-activated coupling. As a reference system, the ligand was directly coupled to the silanised surface. Non-specific protein adsorption, specific binding of antibodies and regeneration were monitored by evaluation of reflectance spectra obtained by white light interference at a thin silica layer (RifS). All polymer modified layers showed improved properties compared to those with direct attachment of the hapten. The non-specific adsorption was reduced to 5-50%. Binding of a specific antibody was significantly increased by the polymer modification: Mass transport limited binding of the specific antibody in low concentrations (30 nM) up to a surface coverage value of 2 ng/mm2 and a maximum surface coverage in the range of a monolayer of IgG (5-6 ng/mm2) was observed for most of the polymers. The surface coverage found for IgG bound specifically to the dextran-modified surface exceeded a protein monolayer.

Unexpected solute aggregation in water on dilution

Studies on cluster-cluster aggregation phenomena in aqueous solutions of fullerene-cyclodextrin conjugates, beta-cyclodextrin, sodium chloride, sodium guanosine monophosphate, and a DNA oligonucleotide revealed that there are larger aggregates existent in dilute aqueous solutions than in more concentrated solutions.

Modification of the biocompatible and haemocompatible properties of polymer substrates by plasma-deposited fluorocarbon coatings

The polymerization of gases present in a low temperature plasma is a technique particularly well suited for biomedical material processing. Therefore, the possibilities this technique offers to increase the biocompatibility and haemocompatibility of polysulphone and poly(hydroxybutyrate) membranes to be used in a new bioartificial pancreas device were studied. The deposition of thin fluorocarbon coatings from an argon plasma containing perfluorohexane gave very smooth and hydrophobic surfaces without affecting the filtering properties of the treated membranes. Adding hydrogen increased the reaction yield, but gave rougher and less hydrophobic coatings. We characterized the biological properties of the treated surfaces and discussed the influence of the modified surface properties on the biological behaviour of the treated polymers. The good biocompatibility of the deposited coatings was established by following in vitro the insulin secretion of Langerhans islets cultured on the treated membranes and by examining the fibrous capsule that developed on plasma-treated polymer disks after three months of in vivo incubation in the peritoneum of Wistar rats. Rough and haemocompatible films of poly(hydroxybutyrate) and smoother, but more thrombogenic, polysulphone films were treated by perfluorohexane and perfluorohexane + H2 plasmas to study the relative influence of surface roughness and surface energy on polymer thrombogenicity. In vitro protein adsorption and total blood clotting tests proved that the surface roughness influences the thrombogenicity more than the other surface properties. This study seems to show that the plasma deposition of smooth and hydrophobic fluorocarbon coatings can increase the biocompatibility and reduce the surface thrombogenicity of the treated membranes without affecting their filtering properties.

[Polyreactions--mechanisms, taxonomy, relevance]

Polyreactions are the prerequisite of life and genetics and are also the basis of all processes for the production of plastics. In this article, an actualized classification of polyreactions based on the reaction mechanism is discussed with a differentiation in chain and step polyreactions. Besides the explanation of the mechanisms of radical, ionic, and coordination polyreactions, polyaddition and polycondensation reactions are covered. In addition, metathesis, polyelimination as well as photochemical and radiochemical polyreactions are considered. Finally, the influence of the reaction mechanism on the properties of materials and the relevance of polyreactions in biology are investigated.

Biocompatibility correlation of polymeric materials using human osteosarcoma cells

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 degrees and 20 degrees for advancing and receding probes, respectively.

Nanoencapsulation of [60] fullerene by a novel sugar-based polymer

[60] Fullerene has been nanoencapsulated by the formation of an inclusion complex with a beta-cyclodextrin-containing lactose copolymer. The cyclodextrin polymer was synthesized by reaction of beta-cyclodextrin chlorotriazine with beta-lactose, and the polymer was highly soluble in water. Encapsulation of the carbon allotrope was achieved by forming a stable inclusion complex between the water-soluble cyclodextrin and [60] fullerene by a new synthetic procedure. Preliminary studies indicate that this complex has potential for biomedical applications because of its radical scavenging properties.

Polymer materials in biosensors

Fundamentals and application examples of polymeric materials in different types of biosensors and presented and discussed in view of their molecular structure and biosensor design and construction. The role of a series of polymers with respect to their typical application and their specific properties, like sensitivity and stability, is highlighted. Future trends of polymer materials for biosensors in the area of medical and environmental applications are outlined.

[Biogenic organochlorine compounds--occurrence, function and ecological relevance]

Organic chlorinated compounds are of increasing interest due to their almost ubiquitous occurrence in the biosphere, their toxic and cancerogenic activity, and their environmental relevance. Despite the relatively high level of knowledge on anthropogenic chlorine compounds, knowledge about biogenic chlorine compounds is comparatively poor. This is astonishing because the quantity of natural emissions of particular organic chlorinated compounds into the ecosphere exceeds that from industrial production considerably. An overview of the occurrence, biosynthesis, and ecological significance of biogenic chlorine-containing organics is given in this article. Results of recent investigations on this topic are discussed and the natural elimination processes of organic chlorinated compounds presented.