Abstract

Nanotechnology is a growing field that represents a large financial market with many industrial and consumer applications. Nanoparticles are widely known to be toxic when inhaled, regardless of chemical composition. This is in contradiction with currently held theory which ascribes a chemical cause to the toxicity of fine particles. This study proposes that fine and ultra-fine particle toxicity is caused by the presence of trapped charges in defects at the particle surface. Through a physical mechanism of action, these charges are transferred generating reactive oxygen species and inducing biological damage. Samples of metal-free phthalocyanine were heated in I2, O2, or EtOh vapor in order to withdraw or inject electrons at point defects respectively to alter their electronic properties. In vitro toxicity of both fumigated and untreated materials was then analyzed using THP-1 cell assays in collaboration with the University of Montana. Results were then compared to determine the contribution of trapped charges at defects to toxicity. Treated H2Pc was found to cause a higher degree of oxidative stress than untreated material in all cases. Toxicity was also shown to increase with grinding and decreased particle size. The purpose of this research is to create a framework for developing a physical set of criteria useful in determining the toxicity of nanomaterials that may be analyzed without the use of expensive, time-consuming biological methods.

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