Post-doctoral position available
A postdoctoral position is available starting approximately August, 2004 to study the potential
health hazards of quantum dots released into the soil where they may contact bacteria and
biofilms.
This work is funded by the U.S. Environmental Protection Agency under the program Impacts of
Manufactured Nanomaterials on Human Health and the Environment. The Co-PI of this work is
Trish Holden at the University of California, Santa Barbara.
Title and abstract of proposal:
Transformations of Biologically-Conjugated CdSe Quantum Dots Released into Water and
Biofilms
Semiconductor nanocrystals (quantum dots) 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 have
observed that nucleobase-conjugated CdSe quantum dots were actively taken up by soil and
water bacteria (for example, Bacillus subtilis and Escherichia coli). Effects on microbial viability
attributed to the presence of the quantum dots included slower doubling times, heavy metal
sequestration, and “blebbing” of metals into the environment.
We propose here to quantify these effects using a variety of biologically-conjugated quantum dots
and an assortment of microbial species, monitoring the process of quantum dot uptake and
breakdown and characterizing the breakdown products that result from bacterial metabolism of
these particles. The experiments will be performed in liquid culture media as well as in a biofilm
containing a realistic environmental array of bacteria. Possible hazards to microbial
populations and to humans through contamination of soil and water with quantum dot breakdown
products will be analyzed and quantified.
Work to be performed:
1. Synthesis of quantum dots (QDs) by various methods (optional; many are available)
2. Conjugation of QDs to biomolecules
3. In vitro assays of redox potential, DNA damage, etc.
4. Addition of QDs to cells in vitro and monitoring of damage by fluorescence and electron
microscopy
Requirements:
A PhD earned or nearly completed in physics, chemistry, physical chemistry, microbiology, or
similar. Experience with any of the following techniques is desirable: electrochemistry; advanced
imaging (TEM, AFM); fluorescence, polarization, and/or Raman spectroscopy; bacterial
growth/death assays; in vitro DNA work; proteomics; anaerobic bacterial culture.
To apply, please send your cover letter and CV to jay.nadeau@mcgill.ca