The overall goals of this body of work were to characterize the antimicrobial properties of
magnesium (Mg) metal and nano-magnesium oxide (nMgO) in vitro, to evaluate the in vitro
cytotoxicity of Mg metal, and to incorporate MgO nanoparticles into a polymeric implant coating
and evaluate its in vitro antimicrobial properties.
In the course of this work it was found that Mg metal, Mg-mesh, and nMgO have in vitro
antimicrobial properties that are similar to a bactericidal antibiotic. For Mg metal, the mechanism
of this activity appears to be related to an increase in pH (i.e. a more alkaline environment) and
not an increase in Mg2+. Given that Mg-mesh is a Mg metal powder, the assumption is that it has
the same mechanism of activity as Mg metal. The mechanism of activity for nMgO remains to be
elucidated and may be related to a combination of interaction of the nanoparticles with the
bacteria and the alkaline pH. It was further demonstrated that supernatants from suspensions of
Mg-mesh and nMgO had the same antimicrobial effect as was noted when the particles were
used. The supernatant from Mg-mesh and nMgO was also noted to prevent biofilm formation for
two Staphylococcus strains. Finally, poly-ε-caprolactone (PCL) composites of Mg-mesh
(PCL+Mg-mesh) and nMgO (PCL+nMgO) were produced. Coatings applied to screws inhibited
growth of Escherichia coli and Pseudomonas aeruginosa and in thin disc format inhibited the
growth of Staphylococcus aureus in addition to the E. coli and P. aeruginosa. Pure Mg metal was
noted to have some cytotoxic effect on murine fibroblast and osteoblast cell lines, although this
effect needs to be characterized further. To address the need for an in vivo model for evaluating
implant associated infections, a new closed fracture osteomyelitis model in the femur of the rat
Magnesium, a readily available and inexpensive metal was shown to have antimicrobial
properties that appear to be related to its corrosion products and that nMgO has similar effects.
Incorporation of nMgO into a PCL composite was easily achieved and revealed similar, although not identical antimicrobial results. This work has provided a strong foundation and methodology for further evaluation of Mg based materials and their antimicrobial properties.