Testing samples were made mixing 100 uL of TiO₂NPs suspensions (0.2 mg/mL and 0.02 mg/mL) and vitamins@P25TiO₂NPs (0.2 mg/mL and 0.02 mg/mL) with 100 μL ATCC 29,213 methicillin-sensitive Staphylococcus aureus (MSSA) (10⁷ in PBS, pH 7). Controls were made replacing nanoparticles with the same volume of PBS. The concentrations of nanoparticle suspensions were chosen based on the FDA approved maximal and the minimal amount usually found in sunscreens, which are 20% and 2% (this is equivalent to 0.2 mg/mL and 0.02 mg/mL for nanoparticles suspensions). The cream concentration, on the other hand, was an intermediate value of 10%.

Currently, titanium dioxide as a food additive is classified as GRAS, or “generally recognized as safe.” 

On the other hand, titanium dioxide is a synthetic mineral that is produced through a chemical reaction involving the mineral ilmenite or rutile. It is used in industries such as cosmetics, paint, and sunscreen as a whitening agent and pigment. The manufacturing process of titanium dioxide involves extracting the mineral from ores, purifying it through chemical processes, and then grinding it into a fine powder.