29. Jahrestagung der Deutschen Gesellschaft für Biomaterialien

PD Dr.

Chair

Prof. Dr.

Professor

﻿Antibacterial nanotechnology and thin films on various substrates and flexible textiles

Antimicrobial coatings

Surface modification technologies

Abstract text (incl. figure legends and references) Antibiotics are powerful drugs that are used to treat bacterial infections, and they work by targeting their cell walls or protein synthesis machinery, and interfering with their normal function. However, over- and misuse of these drugs lead to the development of antibiotic-resistant bacteria. Antibiotic resistance is a major issue in modern medicine, and has the potential to impact the health of millions of people around the world. Due to the high cost in the development of new antibiotics, novel antibacterial materials or thin films based on other principles have to be developed to address. Inspired from the antibacterial effect of the nanostructures presented on certain insect wings such as those on dragonfly and cicade, biomimic silicon nanowires (SiNWs) arrays have been proposed as novel anti-microbes surfaces. It was demonstrated that certain SiNWs show high bacteria killing efficiency measured by confocal laser scanning microscopy (Fig. 1), and the suggested mechanisms include mechanical piercing, immobilization of the bacteria, however, there are still adverse results which do not support such suggestions, we believe that more work have to be done to clarify the exact mechanism of the antibacterial effect of the SiNWs. Large area antibacterial SiNWs can be realized on silicon thin films deposited on various substrates and metal foils by scalable wet chemical etching processes. Furthermore, metals such as silver and copper have well-known antimicrobial and antiviral effects, and we demonstrated also scalable electroless plating processes, for the coating of silver or copper thin films on various substrates, respectively, for examples, on textiles, papers and woods (Fig. 2). This opens application in the fields of hospital furnishings, operating room, patient care, face masks, and many more.

Short Talk

Microstructured ta-C coatings for knee joint application

Cell-material interactions

Abstract text (incl. figure legends and references) Introduction Knee joint replacement with a total knee endoprosthesis is one of the most common surgeries in Germany. Tribological wear processes cause formation of PE and metal wear particles as well as emission of metal ions. These can cause complications that require a revision surgery. The use of a hard-on-hard bearing with a low-friction and wear-resistant coating can eliminate PE wear and significantly reduce metal wear and ion emission. Objectives In this research, smooth and microstructured ta-C (tetrahedral amorphous carbon) coatings were tested to investigate their suitability on knee joint replacements. The hypothesis is that the ta-C coating with a laser-generated microstructure can provide good tribological properties as well as biocompatibility and barrier function against ion emission. Materials &amp; Methods The ta-C coatings were deposited using a patented Pulsed Laser Deposition technology. The surface quality was analysed using the 3D confocal microscopy and SEM. Mechanical properties and adhesion were evaluated using nanoindentations and scratch test. The tribological tests were carried out in a tribology cell using calf serum as a lubricant. The barrier effect against the metal ions was investigated using a long-term test in calf serum. Biocompatibility and antibacterial potential were tested with two types of cells and bacteria. Results The ta-C coatings showed the roughness Ra of 5 to 35 nm, hardness up to 60 GPa and adhesion comparable to commercially available coatings. The tribological tests confirm the advantages of microstructures that provide a lower friction coefficient and wear rate. The deposited coatings demonstrated excellent biocompatibility and moderate antibacterial potential. Conclusion Due to the advantageous mechanical and tribological properties as well as excellent biocompatibility, the ta-C coatings show a high potential for application on knee joint replacements and this potential can be enhanced in further studies.

Anti-adhesive and antibacterial hydrogel coatings for short-term implants

Implant associated

Abstract text (incl. figure legends and references) Short-term implants are widely used to achieve a temporary support function of the bone apparatus. For these implants it is desirable that the implants do not bond with the surrounding tissue and the bone itself in order to prevent surgical complications as well as ruptures during removal. An anti-adhesive and antibacterial coating could reduce complications associated with metal removal and reduce the risk of infection. Macromolecular hydrogels present modularly combinable monomers, producing biocompatible, anti-adhesive and antibacterial polymer networks, which can be bonded to different (implant) surfaces. We developed a two-component hydrogel based on (1) an adhesion polymer consisting of acrylamide-based, hydrophilic main monomers and phosphonic acid derivatives and (2) a crosslinkable prepolymer consisting of acrylamide-based, hydrophilic main monomers and benzophenone derivatives as crosslinkers. Cytotoxicity tests (DIN ISO 10993-5) confirmed biocompatibility of the polymers. Primary fibroblasts or tenocytes were seeded on cell culture plates and titanium discs partially coated with polymer. The figure shows that the cells grow exclusively on the uncoated part of the cell culture plate. Also, no cell adhesion occured on the titanium surface coated with polymer. Non-adherent cells were vital, as they adhered and proliferated after transfer to an uncoated titanium plate. The bacterium mainly responsible for infections in the bone osteosynthesis area is Staphylococcus aureus. This bacterial strain was applied diluted in medium on the layers and after 24 h the medium was seeded in different dilutions on agar plates. No CFUs (colony forming units) were detected on the sample incubated on a plate coated with an antibacterial polymer, indicating a clear antimicrobial effect of the polymers. In conclusion, the coatings successfully prevented adhesion of primary cells and inhibited bacterial growth, making them interesting for use on short-term implants.

Antibacterial surface functionalization by silver nano-powder mixed electrical discharge machining of biomaterials

Abstract text (incl. figure legends and references) Introduction Electrical Discharge Machining (EDM) is widely used for machining biomaterials such as stainless steel, titanium and its alloys. In order to reduce biomaterial-associated infections (BAIs), antibacterial coatings are applied. However, coating usually requires additional, time-consuming and cost-intensive processes. As an alternative, powder mixed EDM is investigated, by adding silver nano-powder to the dielectric for process-integrated antibacterial functionalization while shaping biomaterial surfaces. Objectives Shaping biomaterial components and simultaneously alloying a layer on the surface that has a long-term antibacterial effect. Materials &amp; methods During the EDM process, silver nano-powder with a particle size of (50…60) µm is suspended in the dielectric with different concentrations up to 25 g/L to modify Ti6Al4V surfaces by forming alloyed layers containing silver. Staphylococcus aureus and Staphylococcus capitis bacteria, as well as the osteoblasts cell line are used for in vitro antibacterial and biocompatibility investigations, respectively. For in vivo evaluations, a Galleria mellonella infection model is utilized. Results Current in vitro evaluations show promising results in terms of antibacterial effect combined with good biocompatibility. EDM modified surfaces alloyed with silver show significant reduction of the bacterial number and the amount of bacterial clusters compared to EDM modified surfaces without silver and polished surfaces. No negative influence on the osteoblast function was observed. Furthermore, a long-term effect of antibacterial capacity has been demonstrated both in vitro and in vivo. Conclusion Silver nano-powder mixed EDM represents a promising technology to shape biomaterial parts and concurrently modify the surfaces to reduce BAIs with a long-term antibacterial effect.

Novel antimicrobial coating on titanium with stable non-antibiotic quaternary ammonium compounds to prevent implant-associated infection

Infections

Abstract text (incl. figure legends and references) Introduction: Infection of implanted medical devices (biomaterials), like titanium orthopaedic implants, can have disastrous consequences, including removal of the device. These so-called biomaterial-associated infections (BAI) are mainly caused by staphylococci. Objectives: To prevent biofilm formation using a non-antibiotic based strategy, we aimed to develop a novel permanently fixed antimicrobial coating for titanium devices based on stable immobilized quaternary ammonium compounds (QACs). Materials &amp; methods: Medical grade titanium implants were dip-coated in subsequent solutions of hyperbranched polymer, polyethyleneimine and 10 mM sodium iodide, and ethanol. The QAC-coating was characterized using WCA measurements, SEM, FTIR, AFM and XPS. The antimicrobial activity of the coating was evaluated against Staphylococcus aureus and Staphylococcus epidermidis using the JIS Z 2801:2000 surface microbicidal assay. Lastly, we assessed the in vivo antimicrobial activity in a mouse subcutaneous implant infection model with S. aureus administered locally on the QAC-coated implants prior to implantation to mimic contamination during surgery. Results: Detailed material characterization of the titanium samples showed the presence of a homogenous and stable layer at the surface. Moreover, the coating successfully killed S. aureus and S. epidermidis in vitro. The QAC-coating strongly reduced S. aureus colonization of the implant surface as well as of the surrounding tissue, with no apparent macroscopic signs of toxicity or inflammation in the peri-implant tissue at 1 and 4 days after implantation. Conclusion: An antimicrobial coating with stable quaternary ammonium compounds on titanium has been developed which holds promise to prevent BAI. Non-antibiotic-based antimicrobial coatings have great significance in guiding the design of novel antimicrobial coatings in the present, post-antibiotic era. This research was financially supported by Health~Holland/LSH-TKI.

Lecture hall 6

Short Talks 15

Antimicrobial Coatings

Short Talk Session

Short Talks 15
Antimicrobial Coatings

Appointment

Chair

Topic

Programme

Short Talks 15Antimicrobial Coatings

Appointment

Chair

Topic

Programme

Short Talks 15
Antimicrobial Coatings