The National Institute of Biomedical Imaging and Bioengineering (NBIB) has developed a microscope that increases resolution and contrast in thick biological samples. The new microscope improves on its predecessor by combining two-photon laser scanning microscopy (2PM) with instant structured illumination microscopy (ISIM). Key to the development, was including adaptive optics (AO) to rapidly correct distortions.

Left: Graph showing the dye colors and how they are each at distinct wavelengths. Right: Dyes were used to label different molecules in cancer cells and imaged using Stimulated Raman Scattering microscopy.

A major problem that researchers encounter when attempting to image thick tissue samples is it can be difficult to get a clear image. This is not unlike looking down into a pool and seeing a ball at the bottom. The image, seen through the water, doesn't look very crisp. Astronomers have the same problem when attempting to look at distant objects through the earth's atmosphere. The team incorporated the adaptive optics to help solve this problem.

Adaptive optics uses a two-step process to create clearer images. First, since every sample is different, the team measures how a particular sample distorts the light. This information is then used to create a clear image by adjusting a deformable mirror. A key component of the method is two-photon microscopy, used to generate a small point of light deep inside the sample. By moving this light throughout the sample and collecting information on how it is being distorted, the shape of the mirror can be adjusted to cancel out the distortions, thus creating a clear image of the whole sample.

Most of the team's work on improving microscopy technology has been focused on giving scientists the ability to see biological samples ever more clearly in their native 3D environment. This is important for researchers because, as the team leader, Hari Shroff, Ph.D. said, “We have been able to view cell biology at high resolution on a microscope slide for a long time but that's often not how those cells exist in nature. Efficiency and speed are key, the faster we can image live samples and the less we interfere with their environment, the better we can understand how biology truly works.”

For more information, see Zheng et al., Nature Methods, June 19, 2017 doi: 10.1038/nmeth.4337.

Photonics & Imaging Technology Magazine

This article first appeared in the September, 2017 issue of Photonics & Imaging Technology Magazine.

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