In vivo tissue distribution and safety of polyacrylic acid-modified titanium peroxide nanoparticles as novel radiosensitizers.

Polyacrylic acid (PAA)-modified titanium peroxide nanoparticles (PAA-TiO NPs) are promising radiosensitizers. PAA-TiO NPs were synthesized from commercial TiO nanoparticles that were modified with PAA and functionalized by HO treatment. To realize practical clinical uses for PAA-TiO NPs, their tissue distribution and acute toxicity were evaluated using healthy mice and mice bearing tumors derived from xenografted MIAPaCa-2 human pancreatic cancer cells. Healthy mice were injected with PAA-TiO NPs at 25 mg/kg body weight via the tail vein, and tumor-bearing mice were injected either into the tumor locally or via the tail vein. The concentration of PAA-TiO NPs in major organs was determined over time using inductively coupled-plasma atomic emission spectrometry. After 1 h, 12% of the PAA-TiO NP dose had accumulated in the tumor, and 2.8% of the dose remained after 1 week. Such high accumulation could be associated with enhanced permeability and retention effects of the tumor, as PAA-TiO NPs are composed of inorganic particles and polymers, without tumor-targeting molecules. The liver accumulated the largest proportion of the injected nanoparticles, up to 42% in tumor-bearing mice. Blood biochemical parameters were also investigated after intravenous injection of PAA-TiO NPs in healthy mice. PAA-TiO NPs invoked a slight change in various liver-related biochemical parameters, but no liver injury was observed over the practical dose range. In the future, PAA-TiO NPs should be modified to prevent accumulation in the liver and minimize risk to patients.