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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.

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The high number of biomaterial associated infections demands new strategies to prevent this problem. In this study the suitability of nanohydroxyapatite (nanoHA)-based surfaces containing two Brazilian extracts of propolis (green and red ones) to prevent bacterial growth and biofilm formation, as well as its non-cytotoxic nature, was investigated. Optical density, colony forming units and MTT reduction assay were used to assess the materials' antibacterial activity against planktonic and sessile growth of Staphylococcus aureus. NanoHA matrix was able to absorb both types of propolis and the obtained results revealed the antibacterial effectiveness of the novel materials expressed as the reduction of bacterial growth and biofilm formation ability. Additionally, cell culture tests showed the growth of fibroblasts with high metabolic activity and without membrane damage. Therefore, these nanoHA-based surfaces containing natural products deriving from bees may be a promising bioactive biomaterial to be further studied with the aim of application to orthopaedic or dental devices.

Incorporation of QPEI nanoparticles can improve the long-term antibacterial activity of Pulp Canal Sealer EWT without relevant changes in physicochemical and mechanical properties.

An innovative delivery system based on bacteriophages-loaded alginate-nanohydroxyapatite hydrogel was developed as a multifunctional approach for local tissue regeneration and infection prevention and control. Bacteriophages were efficiently encapsulated, without jeopardizing phage viability and functionality, nor affecting hydrogel morphology and chemical composition. Bacteriophage delivery occurred by swelling-disintegration-degradation process of the alginate structure and was influenced by environmental pH. Good tissue response was observed following the implantation of bacteriophages-loaded hydrogels, sustaining their biosafety profile. Bacteriophagesloaded hydrogels did not affect osteoblastic cells' proliferation and morphology. A strong osteogenic and mineralization response was promoted through the implantation of hydrogels system with nanohydroxyapatite. Lastly, bacteriophages-loaded hydrogel showed excellent antimicrobial activity inhibiting the attachment and colonization of multidrug-resistant E. faecalis surrounding and within femoral tissues. This new local delivery approach could be a promising approach to prevent and control bacterial contamination during implantation and bone integration.

Biopolymer-based aerogels can be obtained by supercritical drying of wet gels and endowed with outstanding properties for biomedical applications. Namely, polysaccharide-based aerogels in the form of microparticles are of special interest for wound treatment and can also be loaded with bioactive agents to improve the healing process. However, the production of the precursor gel may be limited by the viscosity of the polysaccharide initial solution. The jet cutting technique is regarded as a suitable processing technique to overcome this problem. In this work, the technological combination of jet cutting and supercritical drying of gels was assessed to produce chitosan aerogel microparticles loaded with vancomycin HCl (antimicrobial agent) for wound healing purposes. The resulting aerogel formulation was evaluated in terms of morphology, textural properties, drug loading, and release profile. Aerogels were also tested for wound application in terms of exudate sorption capacity, antimicrobial activity, hemocompatibility, and cytocompatibility. Overall, the microparticles had excellent textural properties, absorbed high amounts of exudate, and controlled the release of vancomycin HCl, providing sustained antimicrobial activity.

Orthopaedic implant-associated infections are a devastating complication of orthopaedic surgery with a significant impact on patients and healthcare systems. The aims of this work were to describe the patterns of antimicrobial resistance, pathogenicity and virulence of clinical bacterial isolates from orthopaedic implant-associated infections and to further isolate and characterise bacteriophages that are efficient in controlling these bacteria. Staphylococcus aureus, Enterococcus faecalis and Escherichia coli isolated from orthopaedic infections showed multiresistance patterns to the most frequently used antibiotics in clinical settings. The presence of mobile genetic elements (mecA , Tn 916 /Tn 1545 and intl1) and virulence determinants (icaB, cna, hlb, cylLs, cylM, agg, gelE, fsr and fimA) highlighted the pathogenicity of these isolates. Moreover, the isolates belonged to clonal complexes associated with the acquisition of pathogenicity islands and antimicrobial resistance genes by recombination and horizontal gene transfer. Bacteriophages vB_SauM_LM12, vB_EfaS_LM99 and vB_EcoM_JB75 were characterised and their ability to infect clinical isolates of S. aureus, E. faecalis and E. coli , respectively, was assessed. Morphological and genomic analyses revealed that vB_EfaS_LM99 and vB_EcoM_JB75 belong to the Siphoviridae and Myoviridae families, respectively, and no genes associated with lysogeny were found. The bacteriophages showed low latent periods, high burst sizes, broad host ranges and tolerance to several environmental conditions. Moreover, they showed high efficiency and specificity to infect and reduce clinical bacteria, including methicillinresistant S. aureus and vancomycin-resistant enterococci. Therefore, the results obtained suggest that the bacteriophages used in this work are a promising approach to control these pathogens involved in orthopaedic implant-associated infections.