A Trifunctional, Modular Biomaterial Coating: Nonadhesive to Bacteria, Chlorhexidine-Releasing and Tissue-Integrating.

Various potential anti-infection strategies can be thought of for biomaterial implants and devices. Permanent, tissue-integrated implants such as artificial joint prostheses require a different anti-infection strategy than, for instance, removable urinary catheters. The different requirements set to biomaterials implants and devices in different clinical applications call for tailor-made strategies. Here, a modular coating-concept for biomaterials is reported, which in its full, trifunctional form comprises nonadhesiveness to bacteria and antimicrobial release, combined with enhanced tissue integration characteristics. Nonadhesiveness to proteins and bacteria is accomplished by a hydrophilic brush coating (Vitrostealth). The antimicrobial release module is constituted by a chlorhexidine releasing poly(ethylene glycol) diacrylamide based-coating that continues to release its antimicrobial content also when underneath the nonadhesive top-coating. The third module, enhancing tissue integration, is realized by the incorporation of the penta-peptide Glycine-Arginine-Glycine-Aspartic acid-Serine (GRGDS) within the nonadhesive top-coating. Modules function in concert or independently of each other. Specifically, tissue integration by the GRGDS-module does not affect the nonadhesiveness of the Vitrostealth-module toward bovine serum albumin and Staphylococcus aureus, while the antimicrobial release module does not affect tissue-integration by the GRGDS-module. Uniquely, using this modular system, tailor-made anti-infection strategies can thus readily be made for biomaterials in different clinical applications.

Osteoblast integration of dental implant materials after challenge by sub-gingival pathogens: a co-culture study in vitro.

Sub-gingival anaerobic pathogens can colonize an implant surface to compromise osseointegration of dental implants once the soft tissue seal around the neck of an implant is broken. In vitro evaluations of implant materials are usually done in monoculture studies involving either tissue integration or bacterial colonization. Co-culture models, in which tissue cells and bacteria battle simultaneously for estate on an implant surface, have been demonstrated to provide a better in vitro mimic of the clinical situation. Here we aim to compare the surface coverage by U2OS osteoblasts cells prior to and after challenge by two anaerobic sub-gingival pathogens in a co-culture model on differently modified titanium (Ti), titanium-zirconium (TiZr) alloys and zirconia surfaces. Monoculture studies with either U2OS osteoblasts or bacteria were also carried out and indicated significant differences in biofilm formation between the implant materials, but interactions with U2OS osteoblasts were favourable on all materials. Adhering U2OS osteoblasts cells, however, were significantly more displaced from differently modified Ti surfaces by challenging sub-gingival pathogens than from TiZr alloys and zirconia variants. Combined with previous work employing a co-culture model consisting of human gingival fibroblasts and supra-gingival oral bacteria, results point to a different material selection to stimulate the formation of a soft tissue seal as compared to preservation of osseointegration under the unsterile conditions of the oral cavity.