Staphylococcus comprises up to two-thirds of all pathogens in orthopedic implant infections and they are the principal causative agents of two major types of infection affecting bone: septic arthritis and osteomyelitis, which involve the inflammatory destruction of joint and bone. Bacterial adhesion is the first and most important step in implant infection. It is a complex process influenced by environmental factors, bacterial properties, material surface properties and by the presence of serum or tissue proteins. Properties of the substrate, such as chemical composition of the material, surface charge, hydrophobicity, surface roughness and the presence of specific proteins at the surface, are all thought to be important in the initial cell attachment process. The biofilm mode of growth of infecting bacteria on an implant surface protects the organisms from the host immune system and antibiotic therapy. The research for novel therapeutic strategies is incited by the emergence of antibiotic-resistant bacteria. This work will provide an overview of the mechanisms and factors involved in bacterial adhesion, the techniques that are currently being used studying bacterial-material interactions as well as provide insight into future directions in the field.

Tissue engineering has emerged as a possible alternative to current treatments for bone injuries and defects. However, the common tissue engineering approach presents some obstacles to the development of functional tissues, such as insufficient nutrient and metabolite transport and non-homogenous cell distribution. Culture of bone cells in three-dimensional constructs in bioreactor systems is a solution for those problems as it improves mass transport in the culture system. For bone tissue engineering spinner flasks, rotating wall vessels and perfusion systems have been investigated, and based on these, variations that support cell seeding and mechanical stimulation have also been researched. This review aims at providing an overview of the concepts, advantages and future applications of bioreactor systems for bone tissue engineering with emphasis on the design of different perfusion systems and parameters that can be optimized.

A B S T R A C TCeramic/polymer-based biocomposites have emerged as potential biomaterials to fill, replace, repair or regenerate injured or diseased bone, due to their outstanding features in terms of biocompatibility, bioactivity, injectability, and biodegradability. However, these properties can be dependent on the amount of ceramic component present in the polymer-based composite. Therefore, in the present study, the influence of nanohydroxyapatite content (30 to 70 wt%) on alginate-based hydrogels was studied in order to evaluate the best formulation for maximizing bone tissue regeneration. The composite system was characterized in terms of physic-chemical properties and biological response, with in vitro cytocompatibility assessment with human osteoblastic cells and ex vivo functional evaluation in embryonic chick segmental bone defects. The main morphological characteristics of the alginate network were not affected by the addition of nanohydroxyapatite. However, physic-chemical features, like water-swelling rate, stability at extreme pH values, apatite formation, and Ca 2+ release were nanoHA dose-dependent. Within in vitro cytocompatibility assays it was observed that hydrogels with nanoHA 30% content enhanced osteoblastic cells proliferation and expression of osteogenic transcription factors, while those with higher concentrations (50 and 70%) decreased the osteogenic cell response. Ex vivo data underlined the in vitro findings, revealing an enhanced collagenous deposition, trabecular bone formation and matrix mineralization with Alg-nanoHA30 composition, while compositions with higher nanoHA content induced a diminished bone tissue response.The outcomes of this study indicate that nanohydroxyapatite concentration plays a major role in physicchemical properties and biological response of the composite system and the optimization of the components ratio must be met to maximize bone tissue regeneration.