The art of science – the London Research Institute Electron Microscopy Unit

An image of a breast cell on the cover of Nature (used with permission)

“The large blue alien blob crawls across the page. Tentacles shoot out from its body, attaching to anything in its reach…”

It sounds like a scene from a science-fiction movie, but such sights are commonplace to the staff of Cancer Research UK’s London Research Institute (LRI) Electron Microscopy Unit. In this case, the blue blob is a breast cancer cell, featured on the cover of one of the scientific community’s glossiest “glamour magazines”, the journal Nature.

The Electron Microscopy Unit (EMU) spend their days in windowless basement rooms in the LRI, taking pictures of the inner workings of cancer cells and their healthy counterparts. They provide detailed magnified imagery of research specimens allowing our scientists to see what is happening inside and on the surface of cells.

Through their images, they capture life happening on a microscopic scale, down to the level of specific protein molecules or strands of DNA. That’s a vital service for the charity’s researchers.

For example, the breast cancer cell image on the front cover of Nature was taken as part of a study investigating the genes and proteins involved in cancer. Images like this provide a snapshot of what’s taking place within and on the outside of the cell – giving researchers vital clues as to how the cell’s behaving.

We’ve put together a little slide-show of images from the EMU team, set to music.

[youtube=http://www.youtube.com/watch?v=8uWWpdyf6_c]

Capturing such detailed images is a long process, with individual projects taking anything from 6 months to a year to complete, depending on the complexity of the research. And it takes a lot of effort to photograph a cell. First, you need the right equipment…

What’s an electron microscope?
If you looked down the most powerful light microscope in the world, you’d be able to distinguish individual objects that are around 200 nanometres apart – roughly 1/500 the width of a human hair. But objects closer together than that would just merge into one.  This is because the wavelength of visible light is longer than 200 nanometres.

But electron microscopes use beams of electrons, instead of light. The wavelength of these electron beams is much shorter, allowing scientists to see structures as small as 1 nanometre (1 millionth of a millimetre).

There are two types of electron microscopes, creating different types of images for different purposes.  Transmission electron microscopes (TEM) fire beams of electrons straight through prepared samples of cells, picking up fine details of the tiny structures within.  This technique allows scientists to see what’s going on deep within a cell – effectively a “molecule’s eye view”.

Scanning electron microscopy (SEM) is slightly different. Instead of firing beams straight through a sample, the beams are angled so they bounce off the cell surface, providing detailed three-dimensional images.  The image of the breast cancer cell from the Nature cover was taken using this technique.

Preparing samples for SEM
It’s not as simple as just sticking a few cells under a lens. Samples of cells need to be carefully processed to preserve the tiny structures within them, to make sure we see a realistic view of what’s there. And cells are viewed under a vacuum inside the electron microscope (unlike light, electron beams can’t travel well through air). Before this can be done, the water in the cell must be removed, otherwise the vacuum would cause it to explode.

The EMU team preserve samples of cancer cells (or healthy cells) using chemicals or by freezing – a process known as ‘fixation’. For anyone who studied chemistry at school, some of the ingredients used may sound familiar. Acetone (the same chemical used in nail varnish remover) or ethanol (pure alcohol) are used to dehydrate the cells until all the water is removed whilst keeping the cell structures in place.

The alcohol is then removed by placing the cell into a pressure chamber called a Critical Point Dryer. The chamber is filled with liquid carbon dioxide, which pushes out the ethanol. A bit of heat and pressure then turns the carbon dioxide into a gas, leaving a perfectly dry and beautifully preserved specimen.

The sample is then coated with a very fine layer of platinum to prevent the image from becoming distorted when the cell is bombarded by electron beams.

The art of electron microscopy
Electron micrographs are initially black and white – the images you see in the media are creatively coloured after being taken. The EMU team use Adobe Photoshop to add colours and visually enhance their images. But this is only for illustrative purposes and isn’t used for scientific research images.

Pictures from the EMU are submitted to three photo-libraries, and turn up all over the world. As well as Cancer Research UK’s own photo library, images are sent to Wellcome Images and Visuals Unlimited. So next time you see an impressive picture of a cell crawling across the page, check the picture credit. You may be looking at the work of our EMU team.

Kat

With thanks to Frank Dias, Cancer Research UK Senior Intranet editor; Lucy Collinson, Head of Electron Microscopy at the LRI; Anne Weston, Senior Scientific Officer; and Charlotte Collier, Photo Library Officer.