World first for structured illumination microscopy


Rebecca Pool

Thursday, May 2, 2019 - 15:00
Image: Professor Sara Abrahamsson is building the world's first multi-focus structured illumination microscope for 3D live cell imaging. [Gustav Pettersson]
US-based microscopist, Professor Sara Abrahamsson, is to build and test the first multi-focus structured illumination microscope, designed for 3D live cell imaging.
The instrument eliminates sequential focal scanning in wide-field imaging by simultaneous forming a 3D focal stack of 2D images.
As part of the set-up, Abrahamsson designed a glass diffractive optical element that was placed in a Fourier plane of a wide-field microscope to multiplex and focus-shift the microscope image, and form the image stack.
In 2017, Abrahamsson then showed that multi-focus (MF) microscopy could be combined with structured illumination microscopy (SIM) to deliver fast volumetric super-resolution imaging.
The proof-of-concept system MF-SIM optical system was implemented as a modular add-on to the commercial SIM microscope Zeiss Elyra PS1.
But as Abrahamsson highlights: “Now we want to build the microscope and show that it works for 3D imaging of living cells with super-resolution."
Having won a $700,000 major research instrumentation grant from the National Science Foundation to fund the project, Abrahamsson and colleagues will fabricate the multi-focus microscopy diffractive gratings at a nanofabrication facility at UC Santa Barbara.
According to Abrahamsson's graduate student, Eduardo Hirata-Miyasaki, these gratings can be easily customised to suit the region of interest and the target depth of a sample.
Hirata has already developed an extended version of MFM - the M25 - which increases the number of focal planes from nine to 25 and uses separate cameras to capture the images from each focal plane.
The M25 multi-focus microscope uses separate cameras to capture images from 25 focal planes at different depths in a sample. [Eduardo Hirata]
Designed for functional imaging of living neural circuits of the brain and spinal cord, this instrument does not have super-resolution capability, but can record live 3D volumes at more than 100 frames per second.
"The M25 images simultaneously at 25 different depths, and we can vary the separation between those focal planes,” he says. “Having more focal planes allows us to image greater volumes with higher resolutions.”
"I can't wait to see my collaborators take the first data set of living cells on the MF-SIM that we are building,” adds Abrahamsson. “Who knows what they are going to be able to discover with it?".
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