Nanotechnology Project

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Environment, Health and Safety Research

Bioavailability and Fates of CdSe and TiO2 Nanoparticles in Eukaryotes and Bacteria

Project Information

Principal InvestigatorPatricia A Holden
InstitutionUniversity of California
Project URLView
Relevance to ImplicationsHigh
Class of NanomaterialEngineered Nanomaterials
Impact SectorEnvironment
Broad Research Categories Hazard
Generation, Dispersion, Transformation etc.
NNI identifier

Funding Information

Anticipated Total Funding$399,986.00
Annual Funding$133,328.67
Funding SourceEPA
Funding MechanismExtramural
Funding SectorGovernment
Start Year2006
Anticipated End Year2009



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.

Expected Results:

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.