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Biofilm formation on biomedical devices such as dental implants can result in serious infections and finally in device failure. Polymer coatings which provide antimicrobial action to surfaces without compromising the compatibility with human tissue are of great interest. Copolymers of 4-vinyl-N-hexylpyridinium bromide and dimethyl(2-methacryloyloxyethyl) phosphonate are interesting candidates in this respect. These copolymers form ultrathin polycationic layers on titanium surfaces. As the copolymerization reaction is almost ideal statistical, copolymers with varying compositions can be synthesized and immobilized onto titanium surfaces for comprehensive screening concerning antimicrobial activity and biocompatibility. Copolymer films on titanium were characterized by contact angle measurements, ellipsometry and X-ray photoelectron spectroscopy. Antibacterial properties were assessed by investigation of adherence of S. mutans which represents a strain found in the human oral cavity. Biocompatibility was rated based on human gingival fibroblast adhesion, proliferation and cell morphology. Depending on polymer composition the coatings displayed a behavior ranging from biocompatibility equal to titanium but no antibacterial action to highly antimicrobial activity but poor biocompatibility. By balancing these two opposing effects by tailoring chemical composition, copolymer coatings were fabricated, which were able to inhibit the growth of S. mutans on the surface significantly but still show a sufficient attachment of gingival fibroblasts.

The clinical implementation of percutaneous implants is still limited owing to infections at the side of the stoma. In our concept, this issue is addressed by designing copolymer surface coatings possessing biocompatibility and antimicrobial activity to improve the maintenance of a physiological skin seal at the skin-implant interface. Different copolymers with surface-active phosphonate and antimicrobial cationic groups were designed. Thus, coated titanium samples were cultured with bacterial strains or fibroblasts, respectively. Antimicrobial impact was evaluated by imaging the reduction of bacterial adherence. Biocompatibility was displayed by fibroblast proliferation and morphology. A variety of copolymers of 4-vinylpyridine with vinylbenzylphosphonate or dimethyl(2-methacryloyloxy-ethyl) phosphonate were prepared by free radical polymerization. The optimized polymer coating (copolymer D) showed a reduction of adherent bacteria up to 95%, with only a slight reduction in the adherence of human fibroblasts compared with blank titanium controls. In this study, we demonstrate in vitro that polymer surface coatings can be simultaneously antimicrobial and biocompatible. We consider this to be a promising technology for the realization of a permanent aseptic percutaneous passage as needed for the advancement of osseointegrated limb prosthesis.

Medical implants made of titanium have a wide variety of applications, ranging from replacement of a single tooth to extraoral maxillofacial prosthetic rehabilitation or hip endoprosthesis. The long‐term success of such osseointegrated titanium implants is endangered by inflammation of periimplant hard or soft tissues caused by a bacterial infection. Therefore, implants should ideally inhibit bacterial adhesion and growth, but allows strong attachment of connective tissues or epithelium at the same time. Antimicrobial polymers like poly(vinyl‐N‐hexylpyridinium bromide) (hexyl‐PVP) are a promising approach as implant coatings to inhibit bacterial adhesion, but little is known about the biocompatibility of these polymers. The aim of the present study was to develop a method for evaluation of the cell acceptance of hexyl‐PVP or copolymers of vinyl‐N‐hexylpyridinium bromide and (4‐vinylbenzyl)phosphonic acid diethylester (poly((hexyl‐VP)‐co‐VBP)) as coating on titanium disks. Primary human gingival fibroblasts were used and biocompatibility was assessed by cell adhesion and proliferation. The cell morphology of the fibroblasts on these surfaces was analyzed by scanning electron microscopy (SEM) and was used as additional criterion. The results indicate no significant differences in adhesion or proliferation rate between primary human gingival fibroblasts seeded on polymer‐coated titanium disks and uncoated titanium disks as a control. Although SEM micrographs displayed moderate differences in cell morphology between the two groups, application of hexyl‐PVP or the corresponding copolymers as antibacterial coatings for medical implants or devices appears to be promising.

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