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Acellular assessments of engineered-manufactured nanoparticle biological surface reactivity
Citation:
DREHER, K. L., D. Dunlap, AND T. Nurkiewicz. Acellular assessments of engineered-manufactured nanoparticle biological surface reactivity. Presented at Society of Toxicology, Salt Lake City, UT, March 07 - 11, 2010.
Impact/Purpose:
We examined the physicochemical properties and surface reactivity of metal oxide NPs (Ti02, Ce02, and Si02) in several acellular assays to examine their "reactive" metal content, nitrosylation potential and ability to deplete nitric oxide (NO).
Description:
It is critical to assess the surface properties and reactivity of engineered-manufactured nanoparticles (NPs) as these will influence their interactions with biological systems, biokinetics and toxicity. We examined the physicochemical properties and surface reactivity of metal oxide NPs (Ti02, Ce02, and Si02) in several acellular assays to examine their "reactive" metal content, nitrosylation potential and ability to deplete nitric oxide (NO). The thiobarbituric acid substance assay (TBARS) was used to examine NP reactive metal content. Newly developed assays assessed NP nitrosylation and NO depletion properties. TBARS and nitrosylation assays were modified to determine photocatalytic properties of NPs. Nanoscale (<100 nm) particles displayed the greatest activity compared to non-nanoscale (>100 nm) in all assays where activity was detected. At equivalent concentrations Si02and Ce02 NPs displayed no endogenous or . photocatalytic activity when examined in either the TBARS or nitrosylation assay. In contrast, at equivalent concentrations Ti02 NPs displayed low levels of detectable endogenous and very high levels of photocatalytic activity in the TBARS assay. Ti02 NP TBARS activity did not correlate with size or surface area as maximal activities were observed in the 25-32 nm size range and were influenced by crystalline structure. NPs displayed variable NO depletion potential (Ce02>Ti02>Si02). Ti02 NO depletion did not correlate with size or surface area as maximal activities were observed in the 25-32 nm size range and were influenced by crystalline structure. In contrast Ce02 NO depletion did correlate with size and surface area. These results demonstrate that the complex biologic effects of NP on oxidative stress, protein modification, cellular function and toxicity preclude a simple prediction based on size and surface area alone. (This abstract does not reflect EPA Policy) Support: NIH R01-ES015022 and RC1-ES018274 (TRN)