Super-resolution 3D microscopy images cells in unprecedented detail
A new ultra-high resolution "nanoscope" is capable of taking 3D images of an entire cell and its constituents in unprecedented detail, an advance that could reveal biological phenomena never before seen and bring new medical insights. The work was carried out by various universities and institutions.
The technology incorporates several innovations in fluorescence microscopy and super-resolution microscopy and harnesses the same kind of "adaptive optics" technology used in astronomy, deformable mirrors that change shape to compensate for light distortion.
In astronomy the deformable mirrors are used to compensate for atmospheric distortion to yield clear images of celestial objects. Deformable mirrors also can be used to counteract the distortion caused when light passes through biological tissue.
The technology was demonstrated by imaging cellular components, including synaptonemal complexes, which link chromosomes together; mitochondria and the endoplasmic reticulum, which are critical for cellular functions; the cilia, which protrude from cells like tiny antennas; and bacteriophages, which are viruses about 50 nanometers in diameter that infect bacteria.
The new system advances the original super-resolution fluorescence microscopy by incorporating the deformable mirrors into a microscope using two objectives, one above and one below the sample, and introducing a set of new algorithms to pinpoint molecular positions of proteins deep inside cells.
The system allows researchers to resolve details far smaller than the wavelength of light, representing a powerful and versatile new laboratory tool, Huang said.
"The wave nature of light restricts the resolution of conventional light microscopy to about 200 nanometers, making details of subcellular structures and protein assemblies unresolvable," Huang said.
The new system, however, allows imaging of cellular constituents in 3-D at 10- to 20-nanometer resolution throughout entire mammalian cells, powerful enough to reconstruct the fine features of viruses. Until now, resolving such fine details was only possible using electron microscopy, which requires samples to be treated, killing the cells.
"One goal is to further push the envelope in the direction of live-cell and tissue imaging, two major roadblocks of modern super-resolution techniques," Huang said, "and therefore allow visualization of cellular functions live in their physiological conditions at the nanoscale."
Molecules inside cells and in structures called organelles can be tagged with either "photo-switchable" fluorescent proteins or organic dyes that are able to glow when exposed to a small amount of ultraviolet light.
"These special fluorescent tags (fluorophores) have two states, on and off," Huang said. "And you can control the on and off states by shining light on these molecules. The concept of single molecule switching nanoscopy is to stochastically switch molecules on and off at different time frames, pinpoint the exact locations of single molecules and reconstruct the cellular constituents at super resolution."
The super-resolved images are reconstructed from the positions of thousands to millions of single molecules.
"We are interested in using our developments to study the cytokinetic apparatus, a core machinery during cell division," Huang Said.