Collaborative Research: Linking metal nanoparticle chemical modifications at the luminal/intestinal epithelia interface to intracellular alterations of essential metal homeostasis

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The increase in global metal nanoparticle production, due to the vast array of applications they can be used in and the technological advancements they bring about, raises questions about their potential impact on human health and the environment. The cell has evolved to tightly regulate the uptake and intracellular concentration of essential and toxic metal ions; however, metal nanoparticles seem to bypass these normal uptake systems and accumulate in the cell in a less controlled manner. Determining the exposure scenarios that enhance or reduce metal nanoparticle uptake, bio-reactivity, and toxicity is often difficult due to the lack of appropriate biological models. To allow for such investigations at the cellular level, this research project uses a model of the fish intestine derived from rainbow trout (Oncorhynchus mykiss). Once inside the cell, the bio-reactivity and toxicity of nanoparticles depends on their chemical transformation, a process which is currently poorly understood. This research project endeavors to link the dynamic chemical modifications of metal nanoparticles outside and inside the cell and intracellular alterations of essential metal homeostasis. The mechanistic knowledge generated in this project is envisioned to support human and environmental risk assessment with regard to metal ions and metal nanoparticle exposure. Moreover, the development of the fish intestine model will benefit regulatory science by potentially reducing the cost of testing and contributing to the efforts to establish animal-free alternatives in toxicology risk assessment. This multidisciplinary project is an opportunity for valuable collaborative training for two graduate research assistants and multiple undergraduate research assistants. This research project is designed to evaluate the impact of metal nanoparticles on the homeostasis of essential trace metals. Temporal and spatial distributions of essential and non-essential metals are being correlated to intracellular biomarker of metal bioavailability, establishing a link between intracellular chemical modifications and biological responses. While it is possible to determine dissolved metal speciation outside the cell using simplified cell culture media and chemical equilibrium models, intracellular metal speciation is more difficult to ascertain. Accurate evaluation of intracellular metal speciation requires a technique that allows for in situ measurement such as X-ray spectroscopy and microscopy. This research project studies how to link extracellular silver and titania nanoparticles behavior (agglomeration, dissolution, and speciation of dissolved metal ions) to intracellular chemical modifications induced by metal nanoparticles (levels and localization of essential trace metals) to molecular and cellular responses (mRNA and protein levels of metal transporters and imaging of cellular organelles) in RTgutGC. RTgutGC is a unique intestinal fish cell line that when grown on transwell inserts, develops several of the features found in intestinal epithelia in vivo. Study of cellular localization of metal nanoparticles and local influence on essential metal distribution over time will be valuable from a toxicology/pharmacology standpoint but also in aquaculture, which is now looking into the use of nanotechnologies to improve uptake of nutrients and drugs.