Immunomodulation of surface biofunctionalized 3D printed porous titanium implants.

Additive manufacturing (AM) techniques have provided many opportunities for the rational design of porous metallic biomaterials with complex and precisely controlled topologies that give rise to unprecedented combinations of mechanical, physical, and biological properties. These favorable properties can be enhanced by surface biofunctionalization to enable full tissue regeneration and minimize the risk of implant-associated infections (IAIs). There is, however, an increasing need to investigate the immune responses triggered by surface biofunctionalized AM porous metals. Here, we studied the immunomodulatory effects of AM porous titanium (Ti-6Al-4V) printed using selective laser melting, and of two additional groups consisting of AM implants surface biofunctionalized using plasma electrolytic oxidation (PEO) with/without silver nanoparticles. The responses of human primary macrophages and human mesenchymal stromal cells (hMSCs) were studied in terms of cell viability, cell morphology and biomarkers of macrophage polarization. Non-treated AM porous titanium triggered a strong pro-inflammatory response in macrophages, albeit combined with signs of anti-inflammatory effects. The PEO treatment of AM porous titanium implants showed a higher potential to induce polarization towards a pro-repair macrophage phenotype. We detected no cytotoxicity against hMSCs in any of the groups. However, the incorporation of silver nanoparticles resulted in strong cytotoxicity against attached macrophages. The results of this study indicate the potential immunomodulatory effects of the AM porous titanium enhanced with PEO treatment, and point towards caution and further research when using silver nanoparticles for preventing IAIs.

Femoral prosthesis neck fracture following total hip arthroplasty - a systematic review.

PURPOSE: Head-neck modularity was introduced into total hip arthroplasty to provide more intraoperative surgical options. However, modularity led to new problems, such as trunnionosis and fractures of the femoral prosthesis neck. The purpose of this study was to identify risk factors for hip neck fractures and to provide recommendations to prevent damage and fractures of the neck. METHODS: A systematic review of the literature was performed according to the PRISMA guidelines. RESULTS: Thirty-three case studies were included. Methodologically, most included studies were of moderate or good quality. The 80 neck fractures included in the review took place, on average, 7 years after stem placement. Male gender, high body weight, obesity, previous revision surgery, mixing components from different manufacturers, use of long skirted heads, cobalt-chromium (large size) heads were identified as potential risk factors. CONCLUSION: Hip neck fractures occur on average 7 years after stem placement. The etiology of hip neck fractures is multifactorial. This review revealed several preventable implant- and surgeon-related risk factors.

A chlorhexidine-releasing epoxy-based coating on titanium implants prevents Staphylococcus aureus experimental biomaterial-associated infection.

Prevention of biomaterial-associated infections (BAI) remains a challenging problem, in particular due to the increased risk of resistance development with the current antibiotic-based strategies. Metallic orthopaedic devices, such as non-cemented implants, are often inserted under high mechanical stress. These non-cemented implants cannot be protected by e.g. antibioticreleasing bone cement or other antimicrobial approaches, such as the use of bioactive glass. Therefore, in order to avoid abrasion during implantation procedures, we developed an antimicrobial coating with great mechanical stability for orthopaedic implants, to prevent Staphylococcus aureus BAI. We incorporated 5 and 10 wt % chlorhexidine in a novel mechanically stable epoxy-based coating, designated CHX5 and CHX10, respectively. The coatings displayed potent bactericidal activity in vitro against S. aureus, with over 80 % of the release (19 µg/cm2 for CHX5 and 41 µg/cm2 for CHX10) occurring within the first 24 h. In mice, the CHX10 coating significantly reduced the number of CFU (colony forming units), both on the implants and in the peri-implant tissues, 1 d after S. aureus challenge. The CHX10-coated implants were well-tolerated by the animals, with no signs of toxicity observed by histological analysis. Moreover, the coating significantly reduced the frequency of culture-positive tissues 1 d, and of culture-positive implants 1 and 4 d after challenge. In summary, the chlorhexidine-releasing mechanically stable epoxy-based CHX10 coating prevented implant colonisation and S. aureus BAI in mice and has good prospects for clinical development.

Stability of nano-/microsized particles in deionized water and electroless nickel solutions.

A major problem in the co-deposition of nano- and microsized particles within electroless NiP coatings is particle dispersion in the electroless nickel solution because of the strong tendency of particles toward agglomeration and sedimentation. The stability of colloidal Al(2)O(3), CeO(2), and BN particles and Al(2)O(3)CeO(2) and Al(2)O(3)BN particle mixtures in deionized water and electroless nickel solution was investigated by zeta potential measurements and sedimentation tests. Dispersions of Al(2)O(3) and CeO(2) particles showed good stability in deionized water with zeta potential values of 55 and 39 mV, respectively. BN dispersion in deionized water was found to be relatively unstable at pH 4 with zeta potential values of -13 mV, but at higher pH (i.e., pH 5.5), the values decreased up to about -40 mV. When the dispersions were made in electroless nickel solution, a significant decrease of the zeta potential values was observed for both single particles and mixtures of particles, indicating a change in the surface charge from high positive to low negative with detrimental effects on dispersion stability. Further, the findings suggested that the stability of particle mixtures is dominated by one type of particle, i.e., the Al(2)O(3)CeO(2) dispersion is governed by the single CeO(2) particles, whereas the Al(2)O(3)BN dispersion is governed by the Al(2)O(3) particles. All the zeta potential measurements were in line with the results of the sedimentation tests (i.e., low zeta potential values corresponded to short settling times, whereas high zeta potential values corresponded to long settling times).