Caption: Mouse brain tissue as viewed by traditional microscopy (left) and expansion microscopy (right), which makes it possible to visualize individual synapses (example in white box). In both views, green indicates neurons; blue, pre-synaptic proteins; and red, post-synaptic proteins.
Credit: Ed Boyden, Fei Chen, Paul Tillberg, MIT
Light microscopy has been a mainstay of neuroscience and many areas of biology for more than a century. But the resolution limit of light, based on immutable physical principles, has kept the fine details of many structures out of view. Scientists can’t change the laws of physics—but NIH-supported researchers recently devised a highly creative way to see images that were previously out of reach, by expanding the contents of tissue sections up to five times their normal size, while maintaining the anatomic arrangements. The new approach takes advantage of a compound used in—get this—disposable diapers!
By harnessing the super-absorbent properties of sodium polyacrylate, a polymer commonly used in diapers, a team from the Massachusetts Institute of Technology (MIT) developed a new technique that makes it possible for conventional microscopes to produce super high-resolution images of brain cells. The name of the new technique? Expansion microscopy.
To create such images, MIT neuroscientist Ed Boyden, along with graduate students Fei Chen and Paul Tillberg, start by labeling proteins of interest with fluorescent antibodies. The sample is then embedded within a 3D mesh of sodium polyacrylate, with the fluorescent molecules on the antibodies connecting to the sodium polyacrylate. The proteins are dissolved, leaving the fluorescent labels attached to the expandable polymer. The researchers then add water, and the polymer matrix swells evenly in three dimensions just as it does in a diaper.
The views, opinions and positions expressed by these authors and blogs are theirs and do not necessarily represent that of the Bioethics Research Library and Kennedy Institute of Ethics or Georgetown University.