Scientists have developed a new technique that can expand the tissues of brain by physically magnifying them in order to get a clearer view of the nanoscale structures even with an ordinary light microscope.
The new method, dubbed expansion microscopy, was developed by the researchers at the Massachusetts Institute of Technology (MIT).
The invention of microscope in the 17th century has immensely helped the scientists and researchers to clearly look into the tiniest objects that were otherwise not visible to the naked eye. But the ordinary light microscopes still have certain limitations as they cannot magnify objects that are smaller than nearly 200 nanometres (nm, or millionths of a millimetre) or about half the wavelength of visible red light, which make them look blur under the device lense.
However, this so-called diffraction limit was broken by the development of super-resolution microscopy in the 20th century. These newer techniques brought down the resolution of light microscopes to nearly 20 nanometres using fluorescent ‘marker’ molecules, which helps in binding to cellular proteins of interest and disclose their location. But these machines are very costly and their operation requires excessive technical expertise.
The new method allows super-resolution imaging using conventional light microscopes.
“We were working very hard using classical super-resolution methods like electron microscopy to look at brain circuits. They were very hard to use and can only visualize objects in two dimensions, so we started thinking it would be useful to expand everything,” said Ed Boyden.
Ed Boyden along with his colleagues Paul Tillberg and Fei Chen has developed the new technique.
The researchers began finding ways to carry expansion of tissue samples physically, bringing them in accordance to the work of late MIT physicist Toyoichi Tanaka, who discovered “smart gels” in 1970s.
Smart gels possess water or other fluids inside a matrix of chain-like polymer molecules. They respond well to the changes in light, temperature, and various other factors and stimuli with dramatic changes in shape or size.
The new method involves first treating the tissues in the brain with fluorescently-labelled antibodies, which bind to certain cellular proteins, and then their infusion with a solution containing sodium acrylate as well as several other chemicals that enable the salt molecules establish a cross-link with each other.
Researchers explained the technique helped in the expansion of the brain tissue to approximately five times its normal size and spare the relative positions of proteins as well as several other cellular structures largely integral.
The scientists have detailed the new magnifying technique online in the journal Science.
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