To date, the treatment of articular cartilage lesions remains challenging. A promising strategy for the development of new regenerative therapies is hybrid bioprinting, combining the principles of developmental biology, biomaterial science, and 3D bioprinting. In this approach, scaffold-free cartilage microtissues with small diameters are used as building blocks, combined with a photo-crosslinkable hydrogel and subsequently bioprinted. Spheroids of human bone marrow-derived mesenchymal stem cells (hBM-MSC) are created using a high-throughput microwell system and chondrogenic differentiation is induced during 42 days by applying chondrogenic culture medium and low oxygen tension (5%). Stable and homogeneous cartilage spheroids with a mean diameter of 116 ± 2.80 µm, which is compatible with bioprinting, were created after 14 days of culture and a glycosaminoglycans (GAG)and collagen II-positive extracellular matrix (ECM) was observed. Spheroids were able to assemble at random into a macrotissue, driven by developmental biology tissue fusion processes, and after 72 h of culture, a compact macrotissue was formed. In a directed assembly approach, spheroids were assembled with high spatial control using the bio-ink based extrusion bioprinting approach. Therefore, 14-day spheroids were combined with a photo-crosslinkable methacrylamide-modified gelatin (gelMA) as viscous printing medium to ensure shape fidelity of the printed construct. The photo-initiators Irgacure 2959 and Li-TPO-L were evaluated by assessing their effect on bio-ink properties and the chondrogenic phenotype. The encapsulation in gelMA resulted in further chondrogenic maturation observed by an increased production of GAG and a reduction of collagen I. Moreover, the use of Li-TPO-L lead to constructs with lower stiffness which induced a decrease of collagen I and an increase in GAG and collagen II production. After 3D bioprinting, spheroids remained viable and the cartilage phenotype was maintained. Our findings demonstrate that hBM-MSC spheroids are able to differentiate into cartilage microtissues and display a geometry compatible with 3D bioprinting. Furthermore, for hybrid bioprinting of these spheroids,

No abstract

The objective of this study was the development of Ag-rich antibacterial coatings on titanium (Ti) to prevent post-operative infections. A series of Ag-doped TiO2 coatings were synthesized on Ti discs by plasma electrolytic oxidation (PEO) in an electrolyte containing Ag nanoparticles (AgNPs). The incorporation, distribution and chemical composition of the AgNPs on Ti were determined using scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS). The crystalline structure and wettability of the coating was characterized by X-ray diffraction (XRD) and water contact angle (WCA) analysis respectively. Surface roughness and hardness of the coating were examined using atomic force microscopy (AFM) and Knoop indentation test respectively, while silver ion release was quantified using inductively coupled plasma-mass spectroscopy (ICP-MS).Following PEO, the surface of the Ti substrate was converted to TiO2 composed of anatase and rutile phases. The SEM micrographs showed that the AgNPs were distributed throughout the oxide layer, without changing the morphology of the coating. The coatings also revealed an increased surface roughness, enhanced surface microhardness and improved surface wettability relative to untreated Ti substrates. Furthermore, the incorporation of Ag into the coating did not alter the phase component, surface roughness, microhardness and wettability. A series of in-vitro antibacterial assays indicated that increasing the number of AgNPs in the electrolyte led to excellent antibacterial activities, resulting in a complete reduction of Escherichia coli and a 6-log reduction of Staphylococcus aureus after 24 hours of incubation.

Insufficient glenoid fixation is one of the main reasons for failure in total shoulder arthroplasty. This is predominantly caused by the inert nature of the ultra-high molecular weight polyethylene (UHMWPE) used in the glenoid component of the implant, which makes it difficult to adhesively bind to bone cement or bone. Previous studies have shown that this adhesion can be ameliorated by changing the surface chemistry using plasma technology. An atmospheric pressure plasma jet is used to treat UHMWPE substrates and to modify their surface chemistry. The modifications are investigated using several surface analysis techniques. The adhesion with bone cement is assessed using pull-out tests while osteoblast adhesion and proliferation is also tested making use of several cell viability assays. Additionally, the treated samples are put in simulated body fluid and the resulting calcium phosphate (CaP) deposition is evaluated as a measure of the in vitro bioactivity of the samples. The results show that the plasma modifications result in incorporation of oxygen in the surface, which leads to a significant improved adhesion to bone cement, an enhanced osteoblast proliferation and a more pronounced CaP deposition. The plasma-treated surfaces are therefore promising to act as a shoulder implant.

Er:YAG ablation significantly decreased the microleakage at the tooth-sealant interface compared to the non-invasive technique. The hydrophilic sealant applied on different surface conditions showed comparable result to the conventional resin-based sealant.

No abstract

No abstract

No abstract