Narrow Results

The toxicological effect of TiO₂ nanoparticles with different crystal structure (80 nm for rutile and 155 nm for anatase) on female mice was investigated through intranasal instillation. After exposure for 30 days at the dose of 50 mg/kg body weight, no abnormal activity and mortality were observed with the normally increasing body weight of mice. The coefficients of tissues to body weight also show no obvious difference from the control except the increased coefficient of kidneys in mice exposed to 80 nm TiO₂ nanoparticles. Titanium contents and histopathology examination indicate the no pathological response in the lung was induced by the increased TiO₂ deposition, and the liver, heart, and spleen were not influenced. The severe pathology changes in kidneys suggest that TiO₂ nanoparticles may be excreted out by kidneys via system circulation. However, the serum biochemical parameters were not changed compared with the control, which means no obvious functional impairment induced by the nasal exposure for 30 days. In addition, the higher titanium contents in the brain tissues imply that the translocation and deposition of nanoparticles through intranasal instilling pathway is different from the other routes such as intratracheal inhalation or intratracheal instillation. The influence of deposited nanoparticles on central nervous system needs further investigation and is underway.

The biological effect of ultrasound depends significantly on the sound intensity, frequency and the tissue properties. Both reversible effect and irreversible effect exist. This paper presents some biological and physical explanations, including (1) ultrasound can change the permeation of cell membranes. The stimulation of ultrasound changes the structure of cell, causing the change the electricity of cell membrane; (2) the ultrasound of low frequency can stimulate some plant and animal cells' growth. The pH is indispensable to the growth of cell and ultrasound will change the pH; and (3) we give some ultrasound explanations about the killing effect on cancer cells.