R1 AM Nanotechnology Environmental and Health Impacts
Thursday, 17 November 2005: 8:00 AM - 11:40 AM in Ballroom 1

(HOL-1117-827884) Transformations of Biologically-Conjugated CdSe Quantum Dots Released into Water and Biofilms.

Holden, P¹, Nadeau, J², Stoimenov, P¹, Priester, J¹, ¹ University of California, Santa Barbara, CA, USA² McGill University, Montreal, Quebec, Canada

ABSTRACT- 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. We previously 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. The work here is towards quantifying such 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. Comparisons are made to constitutent dissolved metals to infer toxicity proceses specific to nanoparticles. Liquid culture and unsaturated biofilm format are used for studying a realistic environmental array of bacteria with initial focus on Pseudomonas aeruginosa, an opportuntistic pathogen that is also important in nutrient cycling. Consequences of toxicity to microbial populations through contamination of soil and water with quantum dot breakdown products are projected.

Key words: quantum dots, Pseudomonas aeruginosa, biofilm, soil