In most journals, articles are assigned a couple of keywords, to make them easy to find for other researchers. Much like the "tags" on Gawker posts. This particular article drew my attention thanks to having one of the most intriguing keywords I've ever come across: "artificial microfish". How could I not read futher?
As it turns out, the article is a review of the ways in which micro- and nano-machines can play a role in our efforts toward environmental stability. Things like decontamination of waste sites, water-quality testing, or oil spill clean-ups. It was an interesting read, and maybe worth your time, but since a review paper is already a summary of hundreds of papers, I don't know that my writing a summary of that summary is to anyone's benefit. Instead, I continued tracking down the artificial fish, which led me to this paper from 2013.
Apparently, observing fish behaviour is a pretty standard method of monitoring water toxicity. But it is not without flaws. For one, like all higher order living organisms, every fish is different and reproducibility can be a challenge. For two, there are always ethical considerations when using living animals in lethal experiments. Enter artificial fish. Why they don't just call them artifish is beyond me — what an opportunity missed.
The artifish, as they shall henceforth be known, are made up of polymer-coated gold tubes with enzymes bound to the interior. The enzymes take hydrogen peroxide as fuel and convert it to water and oxygen gas. The generated oxygen gas bubbles out one end of the tube and propels the "fish". The whole thing measure about 8 microns long and 2 microns in diameter (for comparison, a human hair is about 100 microns thick, so these are very small) and, in the absence of pollutants, travels about 54 microns/second.
When in the presence of common environmental toxins, like mercury, copper, sodium azide (used as a propellant in airbags) and aminotriazole (herbicide), the activity of the enzymes is inhibited and the tubes slow down. The researchers used what they (wonderfully) termed "the toxin-microswimmer effect" to get qualitative data, like which toxins are the most potent, as well as quantitative data like the pollutant concentration at which enzyme activity is reduced by 50% (analagous to the LD50 used in live fish testing). Additionally, the artifish respond much faster than real fish to the presence of contaminants because their enzymes are in direct contact with the contaminated water. As a result, these assays take on the order of 10 minutes, a significant improvement over the current multiday studies using real fish.
With all the talk about the potential harm nanotechnology can do, it's refreshing to see there is some progress being made in the other direction as well.
Read the full article, Artificial Enzyme-Powered Microfish for Water-Quality Testing, here.