Imaging cells: New methods enable clear, precise viewing of the interior

In the cinema, the living room, or even the lab, the invisible stimulus makes us guess.

But when it comes to the hidden world of cytochemistry, scientists no longer need to be curious
.
Researchers at the Beckman Institute for Advanced Science and Technology were similarly stimulated to develop an innovative method to "observe" the fine structure and chemical composition
of human cells with unparalleled clarity and precision.
Their technique, which emerged at PNAS earlier this week, employed a creative — counterintuitive — approach
to signal detection.

"Biology is one of the most exciting sciences of our time because there's always been a difference between what we can see and what we can't," said
Rohit Bhargava, a professor of bioengineering at the University of Illinois Urbana-Champaign who led the study.

As the smallest function in our bodies, cells have long captured the attention of researchers, who are interested in
determining what cells make up and where each element resides.
Together, the "what" and "where" form a universal cellular blueprint that can be used to study biology, chemistry, materials, and more
.

Prior to this study, obtaining a high-resolution copy of the blueprint was impossible
.

"Now, more easily than ever before, we can see the chemical details
inside cells at higher resolution," Bargava said.
"This work opens up a range of possibilities, including a new approach to examine the combination
of chemical and physical aspects that control human development and disease.
"

The researchers' work builds on
previous advances in the field of chemical imaging.

Light microscopy uses visible light to illuminate surface features such as color and structure, while chemical imaging uses invisible infrared light to reveal the internal structure
of a sample.

When a cell is exposed to infrared light, its temperature rises and it swells
.
We know from night vision goggles that no two objects absorb infrared wavelengths in exactly the same way; Comparing the Poodle to a park bench is enough to prove that warmer objects emit stronger infrared signals
than cooler objects.
The same is true inside cells, where each molecule absorbs infrared light at a slightly different wavelength and emits a unique chemical signal
.
Studying absorption patterns — a method called spectroscopy — allows researchers to determine the location of
each substance.

Unlike night vision goggles, the researchers did not analyze
absorption modes as spectra.
Instead, they used signal detectors to interpret infrared waves: a tiny beam of light fixed to one end of the microscope, the tip of which scraped the cell surface
like a record player's nanoneedle.

Over the past decade, innovations in spectroscopy have focused on steadily increasing the intensity
of the initial infrared wavelength.

"It's an intuitive approach because we're used to thinking that bigger signals are better
.
We think, 'The stronger the infrared signal, the higher the temperature of the cell, the more it swells and the easier it is to detect,'" Bhargava said
.

There is a considerable setback
behind this approach.
As the cell expands, the movement of the signal detector becomes more exaggerated and creates "noise": so-called static electricity, which hinders precise chemical measurements
.

Seth Keker, a postdoctoral researcher in Professor Bargava's lab and lead author of the study, said: "It's like turning on the FM of a station full of static electricity – the music is getting louder, but so is the static electricity
.
"

In other words, no matter how powerful the infrared signal becomes, the quality of chemical imaging cannot be improved
.

"We needed a solution to stop the noise from increasing as the signal increased," Kenkel said
.

The researchers' remedy for noisy cell imaging is to separate the infrared signal from the motion of the detector, allowing amplification
without adding noise.

Instead of focusing on the strongest possible infrared signal, the researchers began experimenting with the smallest signal they could control to ensure they could effectively implement their solution
before increasing intensity.
According to Kenkel, despite being "counterintuitive," starting small has allowed researchers to respect a decade of spectroscopy research and laid a critical foundation
for the future of the field.

Bhargava likens this approach to a road trip
that goes the wrong way.

"Imagine a spectroscopy researcher sitting in
a car heading to the Grand Canyon.
Of course, everyone will think that the faster the car goes, the faster they will reach their destination
.
But the problem is that the car is heading east from Urbana," he said
.

Increasing the hypothetical car speed is similar to boosting the infrared signal
.

"We parked the car on the side of the road, looked at the map and pointed the car in the right direction
.
Now, the increased velocity — the increased signal — can effectively push the magnetic field forward
.
”

The researchers' "map" enables high-resolution chemical and structural imaging of cells at the nanoscale, which is 100,000 times
smaller than a single hair.
Notably, this technique does not require fluorescent labeling, nor does it require staining molecules to increase their visibility under the microscope
.

While the equipment in the Beckman microscope suite was crucial to the experimental phase of this research, the idea itself did not come from complex technology, but from a culture
that supported curiosity, unconventional problem-solving, and diverse perspectives.

"That's why the Beckman Institute is an amazing place," Bargava said
.
"This project requires ideas
from spectroscopy, mechanical engineering, signal processing and, of course, biology.
You can't seamlessly combine these fields
anywhere other than Beckman.
This study is a classic example
of Beckmann's convergence of interdisciplinary science at the forefront of advanced science and technology.
”