Antibacterial bone substitute of hydroxyapatite and magnesium oxide to

prevent dental and orthopaedic infections​

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Catarina C. Coelho, Rita Araújo, Paulo A. Quadros, Susana R. Sousa, Fernando J. Monteiro

Implant-associated infections represent one of the most serious and concerning problems related with the clinical application of medical devices. With an increasing failure of antibiotic therapy due to resistant microorganisms, it is mandatory to create new and preventive approaches to avoid the development of these infections and consequently reduce patient morbidity and healthcare costs. In this work, antibacterial HAp spherical granules containing different percentages of MgO were developed to be used as bone substitutes and prevent dental and orthopaedic infections. It was observed that granules containing MgO were able to significantly reduce bacterial growth and biofilm formation for both S. aureus and E. coli, when compared with pure HAp materials. In addition, all the produced granules were not cytotoxic in accordance with ISO 10993-5:2009 for biological evaluation of medical devices. The spherical granules were not only biocompatible, but also able to considerably reduce bacterial growth and biofilm formation. In addition, they also presented adequate size, spherical morphology and a long shelf-life that improve their potential for clinical application. The bone substitute produced in this study is a promising material for bone regenerative applications and its potential should be further investigated.

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The antibacterial and angiogenic effect of magnesium oxide in a hydroxyapatite bone substitute

 

Catarina C. Coelho, Tatiana Padrão, Laura Costa, Marta T . Pinto, Paulo C. Costa, Valentina F. Domingues, Paulo A. Quadros, Fernando J. Monteiro & Susana R. Sousa

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Bone graft infections are serious complications in orthopaedics and the growing resistance to antibiotics is increasing the need for antibacterial strategies. The use of magnesium oxide (MgO) is an interesting alternative since it possesses broad-spectrum antibacterial activity. Additionally, magnesium ions also play a role in bone regeneration, which makes MgO more appealing than other metal oxides. Therefore, a bone substitute composed of hydroxyapatite and MgO (HAp/MgO) spherical granules was developed using different sintering heat-treatment cycles to optimize its features. Depending on the sintering temperature, HAp/MgO spherical granules exhibited distinct surface topographies, mechanical strength and degradation profiles, that influenced the in vitro antibacterial activity and cytocompatibility. A proper balance between antibacterial activity and cytocompatibility was achieved with HAp/MgO spherical granules sintered at 1100 ºC. The presence of MgO in these granules was able to significantly reduce bacterial proliferation and simultaneously provide a suitable environment for osteoblasts growth. The angiogenic and inflammation potentials were also assessed using the in vivo chicken embryo chorioallantoic membrane (CAM) model and the spherical granules containing MgO stimulated angiogenesis without increasing inflammation. The outcomes of this study evidence a dual effect of MgO for bone regenerative applications making this material a promising antibacterial bone substitute.

 

 

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