titanates (also known as titanium oxides) are a class of insoluble particulate compounds containing titanium and oxygen with crystalline surfaces that bind metal ions. They offer a means to scavenge metal ions in environmental contexts or deliver them in therapeutic contexts while limiting systemic exposure and toxicity.
To date, the in vitro toxicity of these compounds has been complicated by their particulate nature that interferes with many assays that are optical density (OD)-dependent. Despite this interference, these compounds appear to be inherently nontoxic toward several strains of bacteria.
In contrast, these compounds suppress the succinate dehydrogenase activity of several mammalian cell types by 30-50% compared to unexposed controls. The mechanism is not clear but appears to be based on a combination of binding and delivery of the metal ion to the cells.
The suppression of bacterial growth is less robust than for mammalian cells but is still significant. For example, a small but significant reduction was observed in the growth of skin pathogen Staphylococcus aureus and non-pathogen S. epidermidis for APT-Au(III), Pd(II) and Pt(II) compared to the control bacteria exposed to APT alone.
APT and MST-metal compounds also inhibited the growth of some non-pathogen bacteria including Staphylococcus aureus (unpublished observations). They did not have a significant effect on the growth of S. pyogenes, a causative agent of impetigo and necrotizing fasciitis. However, they did show a modest inhibition of the growth of some oral bacteria compared to the controls.