Zinc Nanoparticle Enhancement of the Olfactory Neuron Response to Odorants Associated with Explosives

Abstract

Many odorants related to manufacturing explosives have low volatilities and have no detectable odor. We found that zinc metal nanoparticles in picomolar concentrations strongly enhanced olfactory receptor neuron responses to odorants related to explosives: Cyclohexanone, Methyl benzoate, Acetophenone, Eugenol. Zinc metal nanoparticles consist of one to two nanometer metallic particles contain 40 to 300 zinc metal atoms, these metal atoms are not in an ionic state. Rat olfactory epithelium was exposed to metal nanoparticles and odorant responses were measured by electroolfactogram (EOG). A small amount of zinc nanoparticles added to explosive odorants strongly increased the odorant response in a dose-dependent manner. In contrast, DMNB (2,3-dimethyl-2,3-dinitrobutane), a volatile organic compound used as a detection taggant for explosives, produced no measurable olfactory response in rat. In physiological experiments enzymatic breakdown of cAMP was prevented by adding the membrane-permeable phosphodiesterase inhibitor IBMX (3-isobutyl-1-methylxanthine). This caused the olfactory cilia cAMP (cyclic adenosine monophosphate) concentration to increase and generated EOG signals. The EOG responses generated by IBMX were not enhanced by zinc nanoparticles. Based on these observations, we hypothesize that zinc nanoparticles are closely located to the interface between the G- protein and the receptor proteins and are involved in transferring signals in the initial events of olfaction. Our results suggest that zinc metal nanoparticles can be used to enhance and sustain the initial olfactory events and can be used for the dog detection of explosive odorants.