National Toxicology Program

Ongoing research activities are focusing on several classes of nanoscale materials:

1. Metal Oxides
2. Fluorescent Crystalline Semiconductors (Quantum dots)
3. Carbon based Fullerenes
4. Carbon Nanotubes
5. Nanoscale silver
6. Nanosale gold

Metal oxides

The focus of these projects is to evaluate nanoscale titanium dioxide and zinc oxide due to their presence in cosmetics.

• Characterization of size, crystallinity, and coating of these metal oxides in representative commercial sunscreens
• Evaluation of photoactivation of titanium dioxide in in vitro, ex vivo, and in vivo models
• Dermal penetration of titanium dioxide in in vivo and in vitro models
• Phototoxicology of titanium dioxide in mice
• Photocarcinogenicity of titanium dioxide in mice

Fluorescent Crystalline Semiconductors (Quantum Dots)

The focus of these projects is to evaluate cadmium selenide/zinc sulfide spheres and rods of varying sizes and surface chemistry as a model system to test hypotheses about role of size and surface chemistry on tissue distribution.

• Synthesis and characterization of specific materials
• Development of quantitative fluorescent microscopy system and IPC-mass spectroscopy approach for evaluating tissue levels
• Quantitative evaluation of the tissue distribution following dermal and systemic routes of exposure

Carbon based Fullerenes

The focus of these projects is to evaluate carbon based fullerenes of varying particle size, fullerene cage size and surface derivatisation.

• Physical and chemical characterization of procured materials and formulation development
• In vivo subchronic repeat dose toxicity studies following inhalation and oral exposure
• Tissue distribution and half life evaluation after subchronic inhalation exposure
• Pulmonary toxicity and evaluations following a single intratracheal instillation
• Immunotoxicological evaluation following inhalation exposure

Carbon Nanotubes

The focus of these projects is to evaluate the impact of variation in length, and diameter on the toxicity of single and multi-walled carbon nanotubes.

• Physical and chemical characterization of commercially available nanotubes.
• In vivo subchronic repeat dose toxicity studies following inhalation exposure.
• Tissue distribution and half life evaluation after subchronic inhalation exposure
• Pulmonary toxicity and evaluations following intratracheal instillation
• Immunotoxicological evaluation following inhalation exposure

Nanoscale silver (NTP Research Concept)

The focus of these projects is to evaluate the impact of particle size on comparative toxicity of nanoscale metallic silver compared to ionic silver. Nanoscale silver is increasingly being used I variety of consumer products based on its antibacterial properties.

• Characterize the relationship between nanoscale silver particle size and degree of ionization to Ag+
• Evaluate the effect of particle size and ionization state on the pharmacokinetic profile of nanoscale silver
• Evaluate the effect of particle size and ionization state on the toxicological profile of nanoscale silver in vivo

Nanoscale gold (NTP Research Concept)

Nanoscale gold is being used as potential platform for nanoscale based therapeutic applications. The focus of these projects is to nderstand how physiochemical properties impact on the disposition, metabolism, elimination and toxicity of nanoscale gold.

• Evaluate the effect of particle size and particle coatings on the pharmacokinetic profile of nanoscale gold
• Evaluate the effect of particle size and particle coatings on the toxicological profile of nanoscale gold in vivo