Characterization of olfactory-enhancing zinc metal nanoparticles

Abstract

Small concentrations of zinc metal nanoparticles (Zn NP) have been shown to significantly enhance the sense of smell in rats [1]. Olfactory enhancement is important to many U.S. agencies where particular interests lie in canine detection for illicit drugs and explosives (DHS and DARPA); the perfume and food industry (DOC); and health-related conditions such as Alzheimer's disease and anosmia (CDC and NIH). Hence, the engineered synthesis and characterization of odor enhancing agents is of great potential importance. Physiological data provides evidence that Zn NPs (nominal diameter 1 nm – 2 nm) enhance the olfactory response in rats, however chemical characterization of these NPs is still necessary to fully understand the enhancement mechanism. Amino acids play a vital role in the signal transduction of neurotransmitters during an olfactory-induced response [2]. Vital information about NP-induced olfactory enhancements may be obtained by assessing interactions between NPs and underivatized amino acids, using capillary electrophoresis (CE) and ultraviolet visible (UV-Vis) spectroscopy. Although the small size of these odor-enhancing Zn NPs present great challenges during analytical measurements, the size and concentration of these Zn NPs were estimated using small angle x-ray scattering (SAXS), dynamic light scattering (DLS) and field emission-scanning electron microscopy (FE-SEM), and found to be approximately 15 nm, in diameter. Inductively coupled plasma-mass spectroscopy (ICP-MS) measurements revealed the presence of Fe (II) and Ni (II) in Zn NP dispersions, which may cause interferences with Zn (II) concentration and dissolution measurements. Zn NP and amino acid interactions, analyzed by UV-Vis spectroscopy, showed that interactions were concentration dependent; higher concentrations of amino acids interacted with more Zn NPs, therefore further investigations of the interactions between NPs and biomolecules is necessary. This work has potential for the development of innovative technologies applicable to the advancement of canine detection, health and performance sciences.