Sep 12, 2013
Nanosilver dims firefly’s light
A new study by researchers in Estonia and the US has revealed that silver nanoparticles can inhibit a luciferase enzyme in fireflies. The work could help us better understand how nanomaterials interact with biological organisms.
Nanosilver is widely used in consumer products thanks to its antimicrobial properties. However, such widespread use means that other microorganisms, aside target bacteria and fungi, would be exposed to these particles too. Micoorganisms in surface water ecosystems and wastewater treatment plant microbial communities could be particularly exposed, as could humans.
Living organisms all have something in common – they contain enzymes (proteins that catalyze complex and specific biochemical reactions at high speeds and at ambient or body temperatures) in their cells. To study the impact of silver nanoparticles (AgNPs) on enzymes we chose firefly luciferase as a model since this enzyme’s activity can easily be measured by recording its light output.
We have found that 20 nm citrate-coated AgNPs inhibit the activity of this enzyme, and that the extent of inhibition depends on the nanoparticle dose. We examined the mechanism behind this effect by characterizing the physicochemical properties of the enzyme and how it biophysically interacted with the AgNPs. We also quantified the amount of silver ions released from the AgNPs during this interaction.
We discovered that mixing the enzyme and AgNPs triggered a red shift of 44 nm in the light absorbance peak of the AgNPs. This produced a so-called luciferase protein corona that was 20 nm thick on the nanoparticle surfaces (figure 1). However, we also found that the secondary structures of the luciferase were only marginally affected upon formation of this corona, something that we verified using circular dichroism spectroscopy and multiscale discrete molecular dynamics simulations.
By comparing the enzymatic inhibitory patterns of AgNPs and Ag-ions we showed that the inhibition was primarily due to silver ions being released from AgNPs. We believe that the fact that silver ions have a high affinity towards Cys residues and nitrogen groups on the enzymes may be the main cause behind the inhibition.
More information can be found in the journal Nanotechnology 24 345101
Magnetic nanoparticles move cells to target (Jan 2008)
New insight into the biocide behaviour of nano silver (Apr 2011)
Antibacterial coatings: taking lessons from nature (Dec 2012)
Interaction of multifunctional silver nanoparticles with living cells (May 2010)
About the author
The study is a joint effort between Estonian and US researchers. Dr. Anne Kahru is the head of the Laboratory of Environmental Toxicology at the National Institute of Chemical Physics and Biophysics in Tallinn, Estonia, and is an expert in nanoecotoxicology. Dr. Monika Mortimer and PhD student Aleksandr Käkinen in the Kahru Lab conduct research on the environmental effects of synthetic nanoparticles. Drs Pu Chun Ke and Feng Ding are affiliated with the Department of Physics and Astronomy at Clemson University in the US. Dr Ke's research examines the biological and environmental implications of nanomaterials and his research has been recognized by an NSF CAREER award and much media coverage. Dr Ding's research is focused on understanding the structure, dynamics and function of proteins and nanoparticle-protein corona through multiscale computer simulations. Dr Pengyu Chen is currently a postdoctoral fellow at the University of Michigan and a former student of Dr Ke’s lab. Dr Chen's research is centred on biosensing, nanomedicine, and environmental remediation using nanomaterials. Financial support for this project was provided by NSF grant no. CBET-1232724 to Pu Chun Ke and EU FP7 NanoValid and ETF grant no. 8561 to Anne Kahru. Special thanks go to a graduate mobility grant from the Archimedes Foundation of Estonia to Aleksandr Käkinen for his stay in the Ke Lab at Clemson University in the US.