The early bird gets the quantum dots

Earthworms are kind of a big deal for environmental scientists. As it turns out, they’re not just food for those early birds – earthworms are detritivores, meaning they feed on dead organic matter and help decompose it, releasing nutrients that were sealed up back into the environment for plants and microbes to use. They’re a key player in the circle of life. However, sediment and soils have a tendency to accumulate a lot of pollutants, making it tough living for soil dwelling animals. Luckily, earthworms are masters at detoxifying pollutants through their unique physiology. Heavy metals, like lead or cadmium, are easily captured and stored away using specialized proteins called metallothioneins. These proteins have a remarkable capacity for binding onto free metals and transporting them away where they can’t cause any harm to sensitive tissues, sequestering them for long periods of time. Metallothioneins are common proteins – even we, humans, have them. What makes the earthworm system special is that the metallothioneins transport the bound metals to the liver (or the earthworm version of the liver, the chloragogen) where it covers the protein-bound metals with layers of amino acids and proteins, most likely to help eventually excrete them later. Earthworms are so good at this that oftentimes entire populations of worms that live in highly contaminated areas become almost completely resistant to the metals. This makes earthworms ideal candidates for cleaning up major chemical spills, remediating and cleaning the environment.

Inside the lowly earthworm lies a metal processing facility like no other. And as it turns out, a nanotechnology factory as well.

Inside the lowly earthworm lies an impressive metal processing facility (and nanomaterial factory). These little guys chomp down on soil, heavy metals and all, and processes them using a series of detoxification proteins called metallothioneins to capture and store toxic metals for safe keeping.

What’s even more interesting, however, is that this same metal detoxification pathway makes them an efficient (and more importantly, cheap) semiconductor factory. Researchers have found that the choragogen provides just the right conditions that allow metals like cadmium and tellurium to react and create tiny (high quality) nanoparticles called quantum dots. These miniscule particles, ranging from 2 to 10 microns across (that’s about 10 to 50 atoms!), are incredibly useful in the tech industry. When quantum dots are hit with a beam of light or have an electric current passed through them, they emit colored light, which happens to be sharper, brighter, and more vibrant than traditional LED lights. If you’ve recently bought a high definition TV then it’s very likely that the display you use to watch your favorite TV shows uses quantum dot display technology. But that’s not all, quantum dots can potentially revolutionize much of the tech industry, changing the way we approach anything from solar panels to lights, inks, and even biomedical technology.

Quantum dots are tiny (2-10 micrometers across!) particles that emit sharp, bright, and vibrant light when hit with light or an electric current. They have diverse uses and are currently used in high definition electronic displays.

Quantum dots are tiny (2-10 micrometers across!) particles that emit sharp, bright, and vibrant light when hit with light or an electric current. They have diverse uses (from solar panels to TV displays) and are a major milestone for the technology industry.

What makes earthworm quantum dots so intriguing (aside from the fact that they come from worms) are the potential biological uses. Remember that layer of amino acids and proteins that the worms use to cover the metallothionein-metal complex? That is what chemists call a passivating layer, which means it helps protect the interior complex but also helps them dissolve and distribute in water. Nanomaterials are notoriously hard to dissolve in water as they tend to clump (much like when you mix oil and water), and as they say, the human body is mostly just water (roughly 60% or so). So any biomedical use needs to find a way to make quantum dots behave in watery bodies. So far all solutions people have come up with either make the quantum dots toxic to living organisms (which kind of defeats the purpose) or alters the quantum dots so much that we see a loss in performance. The humble earthworm seems to have found a way around all of that. Laboratory experiments show that quantum dots made by earthworms are easily dissolved and taken up by mammalian cells in petri dishes, with no signs of any toxic effects.

Rat macrophage-like cells (right) are stained green with quantum dots made by earthworms. On the right are cancer cells green with quantum dots made by earthworms (and nuclei stained blue with a chemical stain). Quantum dots made by earthworms are easily dissolved and distributed into living cells and are not toxic to cells, unlike quantum dots made artificially in a lab, making earthworm quantum dots a potentially important tool in biomedical fields.

Rat macrophage-like cells (left)  and cancer cells (and nuclei stained blue with a chemical stain; right) are stained green with quantum dots made by earthworms. These particles are easily taken into living cells and are not as toxic as man-made quantum dots. Sturzenbaum et al., 2013. Nature Nanotechnology.

To be sure, there’s still a lot of quirks that need to be worked out and much to be learned still about the system before we’ll be seeing earthworm biotechnology farms cropping up (though wouldn’t that be something fun to imagine…). So for now, just bask in the mysterious glow of natural selection and ponder the series of serendipitous events that led to the evolution of a tiny nanotechnology factory within the humble earthworm. That’s certainly enough to keep me busy for a while.

Read more about earthworms and quantum dots doi:10.1038/nnano.2012.232

A Primer: Behavior as a toxicology research tool

Oftentimes when we think about an organism’s health, we don’t really think about including behavior. Maybe it’s just me, but behavior was something associated with the brain, and that thing is just too complicated to think about that they really should just get their own category (which, to be fair, many research groups do separate neurobiology and behavior into their own group, which might contribute to this way of thinking). But, ever since I’ve started my dissertation work, I’ve definitely come around and seen the light – behavior is an incredibly important aspect of physiology and we should all care about it!

Sure, behavior is extremely important part of social interactions; it doesn’t take a scientist to know that. But it’s not always as obvious how behavior is related to your health. Your body comes equipped with many amazing strategies to deal with stress, but it’s your behavior that determines how much stress your body experiences. Changes in behavior are really easy ways for animals to quickly avoid stress. Think about what you’d do if you were stuck outside on a hot summer afternoon. Sure, your body can deal with that stress through all sorts of neat ways like sweating, changing your breathing and heart rate, making new, more heat-sturdy proteins, etc. Or, you could just go find some shade or go inside where it’s air conditioned. Maybe grab an ice cream cone. Your body is capable of some amazing coping mechanisms, but does that mean you have to always use them? A simple change in how you behave can save you a lot in time and energy when dealing with a stressful environment.

More than that though, lots of behaviors may seem really simple on the surface actually involve a lot more than we realize. Let’s use another example – this time imagine yourself as a small fish trying to remain uneaten (a pretty important behavior, if you ask me). The obvious thing to do when a fish senses a predator is to quickly swim away and find somewhere safe to hide out in. Not exactly rocket science. But let’s break that down into the various steps it takes to complete that action. First, you need to realize that the predator is there to begin with. You might see the predator, hear it, or maybe even smell its presence. That requires a fully functional sensory system. Your eyes, ears, nose, and touch receptors need to be on point and they need to transmit that message to your brain. Well, that’s a huge complex system right there so you better be sure your brain is working properly as well. But that’s not all, your brain has to tell your muscles which way to move, and how much to move, so your nervous system needs to be in tip top shape. Your body is also going to help you prepare for this escape by changing its hormone balance. It’s fight or flight, is not a great time to be thinking about making babies or putting on fat reserves, so your endocrine system is going to temporarily turn the dial down on things like sex hormones, growth and fat storage, and instead mobilize stored energy to make sure you have enough fuel to get away. So right there, in this little fish swimming away from a predator, you need a fully functioning sensory organ system, nervous system, endocrine system, and who knows what else – all to tell your body to just keep swimming. Those systems are some key places that a pollutant can muck it all up and cause real problems for a fish (or any animal, really). So as a toxicologist, when I see a fish that’s behaving abnormally, that is a clue that at least one of these systems is off in some way, as well as potentially which areas might have been affected.

Behavior can be complex but with that complexity comes with a wealth of potential for researchers to study. It takes a lot of work, for sure, but behavior is such an important part of an animal’s life that we really shouldn’t be leaving it out anymore. There’s not doubt, studying behavior has many challenges (and the more complex the behavior, the more challenging it becomes), but that just means we have to get creative. In future posts, I’ll be introducing you to the different ways I, and other scientists, study animal behavior and show you some really creative solutions people have come up with to tackle these complex behaviors.

A Primer: your introduction to introductions

What’s a primer? Well, it really depends who you ask. If you ask someone who’s maybe a little more handy or artsy, a primer might be that first coat of paint that goes on before the real color does, either to help the color stick better or to prevent other things like rust from attaching on. If you ask someone who’s a little more mechanically oriented, a primer is a small pump or cap that brings in small amounts of fuel to the engine to get it started. A molecular biologist, like myself, might say that a primer is a small molecule (usually a pair of them) that helps start a polymerization reaction.

Or if you're a real film buff - a primer might be that really really confusing 2004 movie about time travel. These will be much easier to understand. Hopefully....

Or if you’re a real film buff – a primer might be that really really confusing 2004 movie about time travel. These will be much easier to understand. Hopefully….

What these all have in common is that a primer is something that helps get things started; it provides the first bits of fuel or sets up the system so that it’s all ready to go. So for you, dear readers, a primer might be something that serves as an introduction to something scientific. Your brain is the system and I’m providing you that basic knowledge, the starting material, for you to build upon. In this ongoing series of posts (which will be tagged with ‘A Primer’), I’m going to be introducing the background reading, the basic material behind some very important concepts, methods, and procedures that will let you better understand what it is that biologists are doing. Stick around, read up, and let’s see what your mind is ready to do once it’s gotten primed up.