Application of Photocatalyzed TiO₂ for Inactivation of Inhalant Allergens

Allergen avoidance, the most effective strategy against allergic diseases, does not readily apply to indoor inhalant allergens. Capturing and eliminating allergens in the air could be an effective strategy. In this study, we tested the capability of titanium dioxide (TiO₂) to degrade allergens upon activation by a photocatalyst. House dust mite (HDM), cat, and oak pollen extracts were incubated with TiO₂ powder for 24 h in either dark or light exposure.

Changes in protein and allergen content (Der f 1, Fel d 1, and Que ac 1) were investigated by the Bradford assay and a 2-site ELISA. Protein profiles and IgE-reactive components were examined by SDS-PAGE and IgE immunoblotting. Inhibition ELISA was performed to evaluate allergenicity.

Regarding protein concentrations, 69.9% of HDM, 27.1% of cat, and 21.5% of oak pollen proteins were degraded by TiO₂ compared to the allergen extracts incubated in the dark without TiO₂. More specifically, 96.6% of Der f 1 and 81.2% of Fel d 1 were degraded by investigatory rutile TiO₂, as measured by ELISA. However, no significant degradation of Que ac 1 was observed. Immunoblot analyses using mouse monoclonal antibodies against each allergen and IgE antibodies from patients' sera showed diminished allergen bands. In the inhibition ELISA of HDM extract containing various proteases, 87.1% and 96.5% of IgE reactivity was reduced by TiO₂, whereas 47.0% of self-degradation was observed.

TiO₂ eliminated each allergen molecule at a different degradation rate. TiO₂ may be useful in reducing indoor allergenic molecules. However, more detailed studies are needed to optimize its efficacy.