Bioavailability and Fates of CdSe and TiO2 Nanoparticles in Eukaryotes and BacteriaEPA Grant Number: R833323
Title: Bioavailability and Fates of CdSe and TiO2 Nanoparticles in Eukaryotes and Bacteria
Investigators: Holden, Patricia , Nadeau, Jay L. , Stucky, Galen
Institution: University of California - Santa Barbara , McGill University
EPA Project Officer: Carleton, James N
Project Period: May 15, 2007 through May 14, 2010
Project Amount: $399,986
RFA: Exploratory Research: Nanotechnology Research Grants Investigating Environmental and Human Health Effects of Manufactured Nanomaterials: a Joint Research Solicitation-EPA, NSF, NIOSH, NIEHS (2006) RFA Text | Recipients Lists
Research Category: Hazardous Waste/Remediation , Health Effects , Nanotechnology , Health , Safer Chemicals
Semiconductor nanocrystals differ in important ways from bulk semiconductor materials. Their increased band gap means that they function as strong oxidizing and/or reducing agents, and their small size allows them to pass into living cells. Conjugation of biomolecules to the crystal surface can alter any or all of these properties. In preliminary experiments we observed that only bioconjugated CdSe quantum dots are taken up by bacteria and eukaryotic cells. Intracellular fluorescence varies apparently by electron transfer-mediated quenching and nanoparticle breakdown. Bare quantum dots are as toxic to growing bacteria as Cd2+, implying possible extracellular breakdown, but subsequent fates and toxicity relationships are unknown. Particle size dependencies are implied, but insufficiently understood for use in risk analysis. A systematic inquiry into size- and chemistry-dependent uptake and fate processes is needed.
We propose to quantify cellular-scale processes that affect nanoparticle entry, stability, and toxicity for a variety of bacterial and eukaryotic cells. We will focus on two nanoparticles, CdSe whose metals are toxic, and TiO2 whose toxicity arises solely from its size and electron transfer activity. Both short term ‘labeling’ and longer term growth experiments will be performed to quantify particle entry into cells and toxicity. We will also study energy transfer between nanoparticles and energized membranes as a mechanism. The relative importance of near-cell breakdown, whole-particle electron scavanging, and intracellular particle reformation as fates will be quantified.
This project will show how nanoparticles and cells may cooperate in transmembrane transport as well as toxicity. This research will be used to predict cellular-scale exposure and toxicity for bacteria and eukaryotes in soil and water.