Biocompatible surface coating

When living cells come into contact with artificial surfaces, an immunological reaction occurs. This can lead to undesirable reactions. Such a reaction can be reduced or prevented by coating with biogenic compounds. One of these classes of compounds are nitro fatty acids. It has been found that coatings with nitro fatty acids are very suitable, for example, to suppress the immunological reactions that occur in the human body with implants. The problem was that nitro fatty acids, which can easily be applied to artificial surfaces, detach from them again when they come into contact with body fluids. A coating technology was developed in which a bio-degradable polymer can be applied to artificial surfaces in the form of a thin film, which continuously supplies nitro fatty acids to the surface over the duration of the biodegradation. At the same time, the coating protects against corrosion / decomposition of the coated material by aqueous media (e.g. blood or tissue fluids). In this way, on the one hand, a significant improvement in the biocompatibility of implant materials can be achieved and, on the other hand, the corrosion / degradation of implant materials can be influenced.

The contact of human cells with surfaces that are not species-specific leads to an immunological reaction in the sense of inflammation. Unsaturated fatty acids in which one of the double bond-bearing carbon atoms has been nitrated (nitro fatty acids) have immune-stabilizing effects on various cell lines. In fundamental investigations it was found that cells which are coated with nitro fatty acids do not show an immunological reaction in the sense of inflammation or to a significantly lesser extent than on the native surface of foreign materials. It has been shown that this can have advantageous effects on implantable medical devices, such as arterial vessel implants or surgical meshes. It could also be shown that a surface coating consisting of a layer of nitro fatty acids is already sufficient to prevent cell growth that would otherwise take place. If this effect can be maintained over the period of time required for healing in a tissue composite, this can take place practically without scarring. Since the nitro fatty acids can detach from surfaces, a biopolymer was developed in which nitro fatty acids can be absorbed and thus form a reservoir for them, whereby nitro fatty acids that detach or are detached from the surface can be continuously replaced. In the case of implants that are supposed to dissolve again after an implantation, i.e. are made of biodegradable materials, it is desirable that the degradation process only begins after a time delay, e.g. in order not to lose the stability of the material prematurely. Therefore, many of the biodegradable implants must be used in a material thickness that goes well beyond the level that is necessary if the dissolution only takes place after connective tissue penetration. Biodegradation occurs through contact with water. The biodegradable polymer was therefore designed in such a way that it forms a water-impermeable, closed layer on a material surface. It could be shown that the degradation process of a biodegradable implant material can be delayed by a factor of at least 6.

Thus, the biodegradable polymer can produce a significant delay in degradation of implant materials on the one hand and a permanent reduction in the immunological body reaction on the other.

A patent application has been filed for the coating technology (Patent EP3648806A1).