Going platinum

It was a rainy Monday. I held my specimens tightly in hand and walked down Water Street. They were too delicate to trust to my backpack or even my pocket. After working all summer with my intern, Mimi, and then transforming her report into a publishable paper (with a mistake or two along the way), this was the final step - and those specimens needed protection.

I arrived at the Central Microscopy Facility of the Marine Biological Laboratory in Woods Hole, Massachusetts. MBL and WHOI are located right next door to one another and share a lot of resources, most notably our library. WHOI scientists are also allowed to use MBL's electron microscopes, which has benefited me greatly. You see, the last thing I needed for our study on the development of an Arctic deep-sea crinoid was scanning electron microscopy. 

My crinoid specimens on their studs, ready for SEM. Some of them are small 
enough, you can't see them on the studs. This is why we need electrons! 

What is electron microscopy, you ask? The technology is pretty complicated, but the foundational principles are simple. Maybe you remember from high school chemistry class that light has properties of both a particle and a wave. We call light particles "photons." Well, if waves can also be particles, maybe things we traditionally think of as particles can also be waves. This is the case for electrons. They have properties of both particles and waves - which means we can use them to visualize our specimens. Electrons have shorter wavelengths than visible light, so they can resolve smaller structures. We take advantage of this property for microscopy and use electrons to help us see very small structures at high resolution.

Scanning electron microscopy (SEM) is the method we use for imaging solid specimens - things that are 3D objects. The alternative is transmission electron microscopy (TEM), which illuminates transparent samples like tissue sections. In my case, I was looking at 3D specimens of baby crinoids, and I needed SEM. 

To prepare specimens for electron microscopy, you have to coat them with metal so that the electrons something to bounce off of. When I was in grad school, we coated SEM specimens in gold. The joke among the grad students was that we used gold because the more expensive your methods, the better the science. (In reality, gold has some electrical properties that make it preferable for SEM applications.) When I arrived at MBL, I was expecting a similar procedure using gold, but instead, the technician informed me that they use platinum. Ah, yes, the joke must be true. More expense means better science - it has to!

With my specimens sheathed in a uniform 5 nanometer layer of platinum, we loaded them into the microscope. The technician showed me the controls and then let me adjust the settings how I wanted. At the end of a couple hours, I had a folder full of incredible images showing the exact details of my specimens at high resolution. 

I'm very excited to use these SEM images for our crinoid study! Utmost thanks to the MBL technicians who helped with my specimens.

One of the SEM images I took at MBL. This specimen is one of
the older individuals, which has already started developing arms.
It's broken off of its stalk, but you can see the developing calyx
at the top right. Check out the detail of the spikes on the arms!