Stuart Lichtenberg

Stuart Lichtenberg
Major: Agricultural Biotechnology
Class rank/time of internship: Senior
Mentors:Olga Tsyusko and Daniel Starnes 
Collaborations: Environmental Chemistry and Toxicology & Rhizosphere Laboratories, Plant and Soil Science Dept (CAFE)

Title: Sulfidated Silver Nanoparticles Induce Toxicogenomic Effects Distinct from Pristine Silver Nanoparticles and Silver Ions
Project Description:The purpose of my project was to investigate the mechanisms of toxicity of pristine and sulfidized silver nanoparticles (Ag-NPs) on a terrestrial model organism, Caenorhabditis elegans using mutant strains and RNA interference.When released into the environment, pristine Ag-NP are altered from their pristine state, mostly into a sulfidized form.Previous whole-genome microarray-based screens performed by Daniel Starnes, with whom I work closely for this internship, have demonstrated that Ag ions, pristine and sulfidized Ag-NPs each have very distinct toxicogenomic profiles, and therefore likely distinct modes of action. The genes selected for this research were based on these microarray results.Mortality screens were performed on knockout mutants and RNAi knockdown strains of implicated genes in C. elegans.

The overall conclusions from my research:

  • A knockout mutant for a gene associated with metal response showed increased mortality when exposed to Ag ions and pristine Ag-NPs, but not sulfidized Ag-NPs.
  • A knockout mutant for a collagen gene only showed a consistent increase in mortality when exposed to sulfidized Ag-NPs.
  • These findings further support the hypothesis that Ag-NP toxicity is cause by a combination of ion and particle specific effects, and that cuticle damage is a possible mode of toxicity for sulfidized Ag-NPs.

On his internship experience:

How has the internship influenced you?

The internship solidified my resolve to continue my education in graduate school.  I had been considering this path for a long time, but the opportunity to work in an academic laboratory really made me aware that this is what I need to be doing with my career.

If you reflect over what you knew when you started and what you hoped to gain from the experience, did it affirm your plans for continued study/research/major in the area or redirect you?

Prior to the internship, I had thought about continuing doing research in some area of biology, but I had no idea what.  My interests are pretty broad, and this led to some difficulties in deciding what I wanted to do specifically, as specialization becomes somewhat more important as one advances academically.  As I learned more about environmental toxicology, I found that it is a field that will allow me to pursue many of my interests all simultaneously, such as genetics, chemistry, and bioinformatics.  So, the internship showed me a field I had not previously considered, and one that I may pursue for the remainder of my career.

Do you feel you gained valuable skills? 

Absolutely.  Learning to work with C. elegans was an amazing opportunity for me, because it is used in so many different fields, such as genetics, neurology, toxicology, and many more.  My master’s advisor, Jason Unrine, once described it as ‘the ultimate model organism’, due to the sheer number of desirable traits it has for biological research.

What’s next?

I will be continuing my work in the Environmental Chemistry and Toxicology laboratory as a master’s student, working on a new project involving an emerging application of nanoparticles.



© 2013 Tracy Farmer Institute for Sustainability and the Environment