TiO2 eliminates Hymenolepis nana eggs via photocatalytic activity

Titanium dioxide (TiO2) exhibits bactericidal, fungicidal, and virucidal effects under ultraviolet light irradiation. However, there are few reports on the photocatalytic effect of TiO2 against parasitic eggs. This study aims to preliminarily investigate the effect of TiO2 photocatalysis on the inactivation of Hymenolepis nana (H. nana) eggs. We employed the trypan blue staining method to assess the survival rate of 100 insect eggs, investigating the roles of light, TiO2 concentration, solution pH and light intensity in the process of inactivating eggs with TiO2. Morphological and structural damage to the eggs was observed using electron microscopy. The levels of reactive oxygen species (ROS) and adenosine triphosphate (ATP) within the eggs were measured using a fluorescent enzyme labeler, and the infectivity of TiO2-treated eggs was evaluated by oral-gavage in mice (8 mice per group). The results showed that under mercury lamp irradiation, with a TiO2 concentration of 1.0 mg/L, pH values ranging from 6 to 8, light intensity of 0.50 mW/cm2, and photocatalytic exposure for 2 h effectively inactivated H. nana eggs. Electron microscopy revealed that TiO2 photocatalysis caused eggs shrinkage and collapse of the spherical structure, along with the decrease number of mitochondria within the eggs. The TiO2 photocatalysis resulted in an increase in ROS content and a decrease in ATP content in eggs. These findings indicate that TiO2 photocatalysis disrupts the structural integrity and mitochondrial function of H. nana eggs by elevating ROS levels and depleting ATP, while simultaneously reducing the infection rate in mice to 12.5%. This study lays the groundwork for potential future applications of TiO2-based photoenergy-mediated inactivation of parasitic eggs in wastewater and drinking water treatment, ultimately benefiting public health.