Investigating the uptake of nanoparticle-sourced iron by Staphylococcus aureus

Implant-associated infections by antibiotic-resistant biofilm-forming pathogenic bacteria such as Staphylococcus aureus have become a growing concern as they are difficult to treat and lead to implant revision surgery. Implant coatings consisting of superparamagnetic iron oxide nanoparticles may prevent the attachment to and infection of implants by bacteria. However, these nanoparticles release iron, which is also a nutrient necessary for bacterial growth, and may inadvertently contribute to infection. In this thesis the uptake of iron from iron nanoparticles by S. aureus is investigated. 

To achieve this goal, nanoparticles were characterized, separation methods were developed and growth curves were constructed to determine the influence of nanoparticles on the growth of S. aureus. The release and uptake of iron from nanoparticles was investigated through the irradiation of iron nanoparticles and the measurement of the remaining ⁵⁹Fe after nanoparticle-supplemented growth.

It was found that only 3.7 ± 2.4% of nanoparticle iron was taken up by S.aureus after 24 hours, while 53 ± 12% of free iron was taken up. The percentage of iron that was taken up was found to be greater than the weight percentage of iron that was released from the nanoparticles.

While this demonstrates that iron remains with S. aureus after separation. It is not yet known whether this iron is truly internalized, or simply attached to the membrane. It is also not conclusively known whether nanoparticle iron contributes to determine bacterial growth. Therefore, future experiments should be conducted to determine the internalization and the subcellular distribution of radioactive nanoparticle iron and its effects on bacterial metabolism.