Grantee Research Project Results
2005 Progress Report: Transformations of Biologically-Conjugated CdSe Quantum Dots Released Into Water and Biofilms
EPA Grant Number: R831712Title: Transformations of Biologically-Conjugated CdSe Quantum Dots Released Into Water and Biofilms
Investigators: Holden, Patricia , Nadeau, Jay L.
Institution: University of California - Santa Barbara , McGill University
EPA Project Officer: Aja, Hayley
Project Period: October 1, 2004 through September 30, 2007
Project Period Covered by this Report: October 1, 2004 through September 30, 2005
Project Amount: $332,099
RFA: Exploratory Research to Anticipate Future Environmental Issues: Impacts of Manufactured Nanomaterials on Human Health and the Environment (2003) RFA Text | Recipients Lists
Research Category: Nanotechnology , Human Health , Safer Chemicals
Objective:
The objectives of this research project were to: (1) quantify the effects of quantum dots (QDs) on bacteria as they could occur in the natural environment by using a variety of biologically conjugated QDs and an assortment of microbial species; (2) monitor the process of QD uptake and breakdown; and (3) characterize the breakdown products that result from bacterial metabolism of these particles. Possible hazards to microbial populations with extrapolation to humans through contamination of soil and water with QD breakdown products are to be analyzed and quantified.
Progress Summary:
Both Gram-positive and Gram-negative bacteria were studied for their short-term (hours) and long-term (days) responses to biologically conjugated and bare CdSe QDs. Working with Bacillus subtilis and Escherichia coli during short-term experiments, it was observed that light enhanced uptake of biologically conjugated QDs for which cells had specific receptors. DNA damage was inferred from cellular elongation in the absence of division. Membrane damage was observed by transmission electron microscopy (TEM), but repair also occurred over short time scales. Growth of Pseudomonas aeruginosa was slower in the presence of QDs and was similarly slower with cadmium alone, implying breakdown of bare QDs over longer (days) time scales. Biofilms were impacted less negatively and showed similar yields with or without cadmium or QDs. There was early evidence of QD formation when selenite and cadmium were supplied as dissolved salts. A conceptual model of the several fates of QDs in proximity to the cells was developed as an organizing theme and was used for enhancing hypothesis formulation as well as interpretation of results.
Future Activities:
In the coming year, we will: (1) study further the importance of light and the possible light-mediated reactive oxygen species mechanism of membrane damage and short term QD labeling of bacteria (this would help to address one of the key mechanisms of QD entry into cells that is shown in the conceptual model); (2) study further the possibility of DNA damage to bacteria and expand this work to include Gram-negative bacteria; (3) determine definitively if QDs are made in bacteria; (4) study further growth characteristics of bacteria exposed to QDs and to metals (these preliminary experiments are to be replicated to enable quantitative comparisons across treatments); (5) integrate fully high-resolution TEM into the experiments (TEM of nanoparticles requires an ultra-high-resolution instrument and special conditions—an additional experienced collaborator, Randy Mielke from the Jet Propulsion Lab, will be added to assist with this work); (6) study fully the effects of QDs on biofilms; and (7) determine, through inductively coupled plasma analysis of cadmium content, the breakdown of QDs during growth experiments in liquid cultures and in biofilms.
The other activities during Year 2 will include submitting several (three to four) manuscripts for publication, submitting an additional proposal for funding, making numerous presentations of this work at conferences and other venues, and attending the annual all-investigator meeting.
Journal Articles:
No journal articles submitted with this report: View all 50 publications for this projectSupplemental Keywords:
water, soil, chemical transport, effects, ecological effects, bioavailability, metabolism, dose response, organism, population, chemicals, toxics, metals, heavy metals, oxidants, bacteria, terrestrial, aquatic, environmental microbiology, biofilms, chemical analysis, nanotechnology, DNA , Sustainable Industry/Business, treatment, control, Analytical Chemistry, Biochemistry, Chemistry and Materials Science, Environmental Chemistry, Environmental Engineering, New/Innovative technologies, Sustainable Environment, Technology, Technology for Sustainable Environment, DNA damage, biofilm, engineering, environmental sustainability, environmentally applicable nanoparticles, heavy metal sequestration, innovative technologies, innovative technology, nanotechnology, quantum dots, semiconductor nanocrystals,, Sustainable Industry/Business, RFA, Scientific Discipline, TREATMENT/CONTROL, Technology for Sustainable Environment, Sustainable Environment, Environmental Chemistry, Chemistry and Materials Science, Biochemistry, New/Innovative technologies, Environmental Engineering, Technology, sustainability, semiconductor nanocrystals, heavy metal sequestration, environmental sustainability, biofilm, innovative technologies, environmentally applicable nanoparticles, nanotechnology, quantum dots, innovative technology, engineeringProgress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.