Sebastian Grade

Serum albumin reduces the antibacterial and cytotoxic effects of hydrogel-embedded colloidal silver nanoparticles

Although silver nanoparticles (AgNPs) are widely used as ion-releasing antimicrobial additives in medical devices, recent reports indicate the suppression of effectiveness in the presence of blood serum proteins. Bovine serum albumin (BSA) is known to bind silver and silver ions, so that the presence of proteins may change the antibacterial or cytotoxic properties of AgNPs even when they are embedded in a solid agar hydrogel matrix. We produced ligand-free AgNPs by laser ablation in water resulting in aqueous silver mass concentrations of 0.5 to 7.1%. The AgNPs were immersed into agar in concentrations of 5–70 μg ml−1 medium. We examined the influence of 1% BSA within the hydrogel matrix on the nanoparticles’ antibacterial effect on four clinically relevant bacteria strains and the cytotoxicity of colloidal AgNP was tested on fibroblasts with or without 1% BSA. The hydrogel-immobilized AgNPs showed a significant reduction of antibacterial activity in the presence of BSA. Cytotoxicity started at a colloidal AgNP concentration of 35 μg ml−1, and addition of BSA significantly reduced the effect on cell morphology and viability. Overall, in the presence of BSA, both antibacterial and cytotoxic effects of AgNPs were markedly reduced. Notably, a therapeutic AgNP window, requiring a dose at which pathogenic bacteria growth is inhibited while fibroblast viability is not affected, could only be observed in the absence of BSA. Addition of BSA reduces the antibacterial activity of AgNP to a point without significant growth inhibition of S. aureus but still observable cytotoxic effects on HGFib. Hence, the presence of a major blood serum protein significantly decreases the antimicrobial effects of AgNPs on a range of pathogenic bacteria even when the NPs are immobilized within an agar hydrogel model.

Introducing a Semi-Coated Model to Investigate Antibacterial Effects of Biocompatible Polymers on Titanium Surfaces

Peri-implant infections from bacterial biofilms on artificial surfaces are a common threat to all medical implants. They are a handicap for the patient and can lead to implant failure or even life-threatening complications. New implant surfaces have to be developed to reduce biofilm formation and to improve the long-term prognosis of medical implants. The aim of this study was (1) to develop a new method to test the antibacterial efficacy of implant surfaces by direct surface contact and (2) to elucidate whether an innovative antimicrobial copolymer coating of 4-vinyl-N-hexylpyridinium bromide and dimethyl(2-methacryloyloxyethyl) phosphonate (VP:DMMEP 30:70) on titanium is able to reduce the attachment of bacteria prevalent in peri-implant infections. With a new in vitro model with semi-coated titanium discs, we were able to show a dramatic reduction in the adhesion of various pathogenic bacteria (Streptococcus sanguinis, Escherichia coli, Staphylococcus aureus, Staphylococcus epidermidis), completely independently of effects caused by soluble materials. In contrast, soft tissue cells (human gingival or dermis fibroblasts) were less affected by the same coating, despite a moderate reduction in initial adhesion of gingival fibroblasts. These data confirm the hypothesis that VP:DMMEP 30:70 is a promising antibacterial copolymer that may be of use in several clinical applications.

Reduced bacterial adhesion on titanium surfaces micro-structured by ultra-short pulsed laser ablation

Abstract Implant-associated infections still pose serious problems in modern medicine. The development of fabrication processes to generate functional surfaces, which inhibit bacterial attachment, is of major importance. Sharklet™-like as well as grooves and grid micro-structures having similar dimensions were fabricated on the common implant material titanium by ultra-short pulsed laser ablation. Investigations on the biofilm formation of Staphylococcus aureus for up to 24 h revealed similarly reduced bacterial surface coverage on all micro-structures investigated compared to smooth titanium surfaces. This study is a prove-of-principle and could serve as basis for further investigations towards a structure-based biofilm-inhibiting implant.

Structural analysis of in situ biofilm formation on oral titanium implants

Background: The primary etiologic factor for peri-implant infections is the adhesion of biofilms on oral implant surfaces in the area of soft-tissue penetration. The aim of the present study was to examine in situ biofilm growth directly on implant-abutment surfaces without the use of oral splints and to determine the effect of intraoral abutment localization on biofilm growth. Materials and Methods: Fifteen titanium healing abutments were inserted in six patients for 14 days. The newly formed supragingival biofilm on the titanium surface of the healing abutments was stained with fluorescent Live/Dead Baclight kit before examination by confocal laser scanning microscopy. The biofilm was scanned in terms of its surface coverage and thickness and different sites. Results: The results show that the biofilm has a different structure in every patient, with the thickness of the biofilm structure ranging between 0 and 80 ΅m and the surface coverage between 0 and 97% of the abutment surface. There was similar biofilm surface coverage at different intraoral locations, whereas the biofilm was significantly thicker in the mandible as compared to maxillary implant abutments. Conclusion: The method uniquely describes an effective way to depict biofilm development on implant surfaces in the supra- and sub-gingival regions.

In Situ Biofilm Formation on Titanium, Gold Alloy and Zirconia Abutment Materials

Background: Biofilm formation on trans-gingival implant surfaces is a common reason for local inflammation of the peri-implantary tissue and can lead to implant loss. The aim of the current in situ study was to evaluate biofilm formation on titanium, gold alloy and zirconia abutment materials directly in the trans-gingival region. Materials and Methods: Specimens were attached to implant healing abutments and were inserted in 8 patients for 14 days. Confocal laser scanning microscopy was used to measure biofilm height and surface coverage. Results: Titanium showed a mean biofilm height of 10.8 μm and a surface coverage of 26.5%. For gold alloy, a height of 14.6 μm and coverage of 27.3% was found. Zirconia had a biofilm height of 2.7 μm and coverage of 10.5%. No statistically significant difference between the three materials was found. However, zirconia tended to form less biofilm than the other materials. Conclusion: All three materials seem to be suitable for the use as abutment material. Zirconia appeared to have the most favourable biological and aesthetic properties.

Design of Antibacterial Copolymers for Implant Coatings

To develop innovative antibacterial implant sur- faces monomers with different properties have been com- bined as copolymers and modified by alkylation. For most applications resulting copolymer coatings have not only to reduce bacterial adhesion but also make sure that cellular attachment is not affected.