Implant-associated infections represent a serious risk in human medicine and can lead to complications, revisions and in worst cases, amputations. To target these risks, the objective was to design a hybrid implant surface that allows a local burst release of antibiotics combined with long-term antimicrobial activity based on silver. The efficacy should be generated with simultaneous in vitro cytocompatibility. The investigations were performed on titanium K-wires and plates and gentamicin was selected as an illustrative antibiotic. A gentamicin depot (max 553 µg/cm2) was created on the surface using laser structuring. The antibiotic was released within 15 min in phosphate buffered saline (PBS) or agar medium. Metallic silver particles (4 µg/cm2) in a titanium dioxide layer were deposited using plasma vapor deposition (PVD). About 16% of the silver was released within 28 days in the agar medium. The local efficacy of the incorporated silver was demonstrated in a direct contact assay with a reduction of more than 99.99% (Escherichia coli). The local efficacy of the hybrid surface was confirmed in a zone of inhibition (ZOI) assay using Staphylococcus cohnii. The biocompatibility of the hybrid surface was proven using fibroblasts and osteoblasts as cell systems. The hybrid surface design seems to be promising as treatment of implant-associated infections, considering the achieved amount and release behavior of the active ingredients (gentamicin, silver). The generated in vitro results (efficacy, biocompatibility) proofed the concept. Further in vivo studies will be necessary translate the hybrid surface towards clinical applied research.
Improved implant osteointegration offers meaningful potential for orthopedic, spinal, and dental implants. In this study, a laser treatment was used for the structuring of a titanium alloy (Ti6Al4V) surface combined with a titanium dioxide coating, whereby a porous surface was created. The objective was to characterize the pore structure shape, treatment-related metallographic changes, cytocompatibility, and attachment of osteoblast-like cells (MG-63). The treatment generated specific bottleneck pore shapes, offering the potential for the interlocking of osteoblasts within undercuts in the implant surface. The pore dimensions were a bottleneck diameter of 27 µm (SD: 4 µm), an inner pore width of 78 µm (SD: 6 µm), and a pore depth of 129 µm (SD: 8 µm). The introduced energy of the laser changed the metallic structure of the alloy within the heat-affected region (approximately 66 µm) without any indication of a micro cracking formation. The phase of the alloy (microcrystalline alpha + beta) was changed to a martensite alpha phase in the surface region and an alpha + beta phase in the transition region between the pores. The MG-63 cells adhered to the structured titanium surface within 30 min and grew with numerous filopodia over and into the pores over the following days. Cell viability was improved on the structured surface compared to pure titanium, indicating good cytocompatibility. In particular, the demonstrated affinity of MG-63 cells to grow into the pores offers the potential to provide significantly improved implant fixation in further in vivo studies.
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