Antibacterial bone substitute of hydroxyapatite and magnesium oxide to prevent dental and orthopaedic infections.

Bone substitutes market is growing due to the great demand for bone regenerative therapies. However, most of the actual products available in the market are incapable of inhibiting bacterial colonization, which can lead to tissue infection and possible implant failure. Some bone substitutes are combined with antibiotics to avoid the development of implant-associated infections, but the growing bacterial resistance to antibiotics often makes these products ineffective. Therefore, it is mandatory to develop new and alternative approaches. In the present work, a granular bone substitute of hydroxyapatite was produced, where different percentages of magnesium oxide were introduced. The antibacterial activity and biofilm formation was evaluated towards Staphylococcus aureus and Escherichia coli. The inclusion of magnesium oxide particles reduced bacterial growth and biofilm formation in a concentration-dependent manner, when compared with pure hydroxyapatite materials. Superior antibacterial activity and inhibition of biofilm formation was observed for Staphylococcus aureus with complete eradication when magnesium oxide percentages were equal or above 3 wt%. The materials cytotoxicity was assessed under ISO 10993-5:2009 guidance and through Live/Dead cell marking and none of the produced granules was cytotoxic. In addition, reactive oxygen species production was also evaluated and the results revealed that the exposure to the materials extracts did not induce the formation of reactive oxygen species by cells.