Preventing implant-associated infections by silver coating

Implant-associated infections (IAI) are a dreaded complication mainly caused by biofilm-forming staphylococci. Implant surfaces preventing microbial colonization would be desirable. We examined the preventive effect of a silver-coated titanium aluminium niobium (TiAlNb) alloy. The surface elicited a strong, inoculum-dependent activity against Staphylococcus (S.) epidermidis and S. aureus in an agar inhibition assay. Gamma sterilization and alcohol disinfection did not alter the effect. In a tissue cage mouse model, silver coating of TiAlNb cages prevented peri-operative infections in an inoculum-dependent manner, and led to a 100 % prevention rate after challenge with 2 x 106 CFU S. epidermidis/cage. In S. aureus infections, silver coating had only limited effect. Similarly, daptomycin or vancomycin prophylaxis alone did not prevent S. aureus infections. However, silver coating combined with daptomycin or vancomycin prophylaxis thwarted methicillin-resistant S. aureus infections in 100 % or 33%, respectively. Moreover, silver release from the surface was independent of infection and occurred rapidly after implantation. On day 2, a peak of 82 μg Ag/ml was reached in the cage fluid corresponding to almost 6 times the minimal inhibitory concentration of the staphylococci. Cytotoxicity towards leukocytes in the cage was low and temporary. Surrounding tissue did not reveal histological signs of silver toxicity. In vitro, no emergence of silver resistance was observed in several clinical strains of staphylococci upon serial subinhibitory silver exposure. In conclusion, our data demonstrate that silver-coated TiAlNb is potent for preventing IAI and thus can be considered for clinical application

Rings, chains and helices: new antimicrobial silver coordination compounds with (iso-)nicotinic acid derivatives

Complexes with silver ions have great potential for applications in medicine. Appropriate bidentate ligands, binding to silver ions, are able to generate coordination polymers as well as molecular entities as a function of ligand flexibility, conformation and length. Here we present the continuation of our previous studies in this field with ligands based on oligomers of polyethylene glycol, functionalized at both ends with either nicotinic or isonicotinic acid. The structures of three ligands and nine new coordination compounds are presented. A large variety of structures are obtained as a function of counterion, solvent and ligand-to-metal ratio, such as isolated rings, offset stacked rings, parallel chains and entangled chains, and their antimicrobial properties as well as biocompatibility are assessed

Development of a polystyrene sulfonate/silver nanocomposite with self-healing properties for biomaterial applications

A silver polystyrene sulfonate polyelectrolyte was synthesized, showing a spontaneous reduction of silver ions to silver nanoparticles over a period of approximately 1 month. A follow-up of the nanoparticle formation via scanning electron microscopy (SEM) reveals migration of the nanoparticles towards the cracks of the polymer over time, leading to a self-healing process of the nanocomposite. Antibacterial tests show excellent antibacterial activity of our compound, which allows us to use this compound e.g. for external medical applications