The response of human macrophages to 3D printed titanium antibacterial implants does not affect the osteogenic differentiation of hMSCs.

Macrophage responses following the implantation of orthopaedic implants are essential for successful implant integration in the body, partly through intimate crosstalk with human marrow stromal cells (hMSCs) in the process of new bone formation. Additive manufacturing (AM) and plasma electrolytic oxidation (PEO) in the presence of silver nanoparticles (AgNPs) are promising techniques to achieve multifunctional titanium implants. Their osteoimmunomodulatory properties are, however, not yet fully investigated. Here, we studied the effects of implants with AgNPs on human macrophages and the crosstalk between hMSCs and human macrophages when co-cultured in vitro with biofunctionalised AM Ti6Al4V implants. A concentration of 0.3 g/L AgNPs in the PEO electrolyte was found to be optimal for both macrophage viability and inhibition of bacteria growth. These specimens also caused a decrease of the macrophage tissue repair related factor C-C Motif Chemokine Ligand 18 (CCL18). Nevertheless, co-cultured hMSCs could osteogenically differentiate without any adverse effects caused by the presence of macrophages that were previously exposed to the PEO (±AgNPs) surfaces. Further evaluation of these promising implants in a bony in vivo environment with and without infection is highly recommended to prove their potential for clinical use.

Non-Covalently Stabilized Alginate Hydrogels as Functional Cell Scaffold Material.

Biopolymers are an attractive class of compounds for being used in biomedical applications as they are widely available from biomass. Their drawback is the lack of mechanical stability and the ability to tune this properly. Covalent chemical cross-linking is an often used approach but it limits usability due to legislation as well as the need of advanced and specialized knowledge by end users such as clinicians. Here, increased and tunable mechanical properties are achieved of alginate-based hydrogels with non-covalent approaches using linear polyethyleneimine (LPEI) as a polyelectrolyte rather than only multivalent metal ions (Ca2+ ). Gel stiffness increases with increasing LPEI content. Gel morphology changes from a thin fibrous mesh for alginate-Ca2+ to thicker fibrous networks when LPEI is introduced. The gels are able to efficiently release encapsulated small molecular dyes and the gels are able to host cells. For the cell encapsulation human skin fibroblasts (HSkF) and human bone marrow-derived mesenchymal stem cells (hBM-MSC) are used. HSkF can be successfully incorporated without diminished viability while the matrix components and gel preparation method are not compatible with hBM-MSC. The newly developed alginate-based system is regarded as a potential candidate for wound dressing materials.