A new device will help in the imaging of biological samples at the microscopic level

Researchers have developed a spectroscopic microscope to enable optical measurement of molecular coherence and direction in biological samples. The novel measurement method allows researchers to make biological images at a microscopic level faster and more accurately.

The new instrument is based on the special-frequency infrared spectroscopic imaging method developed by researchers at the Beckman Institute for Advanced Science and Technology at the University of Illinois Urbana-Champaign.

This project is about introducing the study of molecular chirality in the microscopic field. “

Rohit Bhargava, Professor, Bioengineering, Director, Cancer Center, Illinois

Molecular chirality refers to the spatial direction of atoms in molecules or multimolecule assemblages. In biological systems, a single molecule may receive a cellular response, while its mirror image may be inactive or even toxic. Although vibrational circular dichroism can be used to help determine the structure and direction of a molecular chemical, VCD measurements are time-intensive and could not have previously been used to produce images of complex biological systems. or samples of tight material.

The paper “Measuring Vibrational Cyclic Dichroism with Infrared Spectroscopic Imaging” was published in Analytical chemistry and appears on the cover.

The novel infrared microscope makes imaging of biomolecule chirality possible by both accelerating build-up time and improving signal-to-sound ratio of traditional VCD methods.

“When you put a light down a microscope from a spectrometer, you’re essentially throwing away a lot of it,” Bhargava said. “For VCD measurements, you also have to put it through a photoelastic converter, which changes the polarity of light to the left or right. At that point, you don’t have much light left, which means you need to average your token for a long time to see just one pixel inside an image. “

The laboratory performed chemical imaging and structures, led by Bargava, achieved fast and coherent infrared and VCD measurements by building on the frame of their high-performance specific frequency infrared image microscope. Instead of employing a traditional thermal light source, the instrument is built around a quantum cascade laser.

“The laser source inspired the entire design,” said Yamuna Phal, a graduate student researcher in electrical and computer engineering. “The QCL source has higher power, which means we can get faster measurements. Previously, you could only do VCD on melt samples, but we can also do hard images. This has never been tried before because it takes so long to get VCD signals in the first place. “

Kevin Yeh, a postgraduate research associate who co-directed the development of the microscope, said other applications could arise from the microscope built for this project. “We first saw the special frequency infrared microscope as a platform on which other methods could be built,” Yeh said. “We’ve solved one of those extensions, which is VCD, but we could think of many more.”

While the use of this method may transcend the biological sciences, the work itself is a testament to the strength of interdisciplinary science. “This project was only possible by bringing together thinking from different fields,” Bhargava said. “It’s a chemistry problem solved by a physics-based design, implemented by an electrical engineering student. It’s in Beckman’s DNA to use that method to solve problems.”