How Nature’s Symmetry Might Help Us See Early Warning Signs of Cancer

Have you ever wondered why animals and humans often have pairs of body parts — like two eyes, two ears and two nostrils? The short answer is that having mirrored sense organs helps us understand our surroundings better.

For example, your eyes sit a little apart, giving your brain two slightly different views. By comparing them, your brain figures out how far away objects are — this is what we call depth perception. Similarly, two ears pick up sounds at slightly different times, which helps you figure out where a sound is coming from.

We see many examples of this concept, known as bilateral symmetry, in nature. This makes us wonder if we can do something similar on the tiny scale of molecules. Scientists design sensors to see molecules, but these sensors usually don’t come in pairs, like our eyes and ears do. So, this leads scientists to the question of what we could see — and measure — if we designed these sensors to work in mirror-image duos, like a pair of eyes. 

The idea of my research is that if we could see molecules from two different perspectives, we could learn more about them. Since our bodies are made up of lots of molecules, this could potentially lead to breakthroughs in medical treatments — including detecting early warning signs of cancer.

As a first step toward making this a reality, a collaborator and I worked to build an ambitious system that can see and measure molecules in a way we haven’t before.

Nature’s Gift: DNA and Carbon Nanotubes

To build this detection system for molecules, we need to make two sensors that act like mirror images of each other. This is tricky, but Mother Nature gives us two good starting materials:

• DNA: We know DNA as the carrier of genetic information, but it can also be used to organize other materials. Natural DNA has a certain twist called D-DNA. Scientists can also create a mirror-image version called L-DNA.
• Carbon nanotubes: These are tiny tubes made from rolled-up sheets of carbon. Some nanotubes twist slightly to the left and others to the right. This twisting affects how they interact with light and how they bind to molecules.

From earlier experiments, we learned that D-DNA can wrap around certain carbon nanotubes and sort themselves by their twist. Because L-DNA is a mirror image of D-DNA, it should wrap around nanotubes that twist in the opposite direction.

My collaborator, Ruojie Sha at New York University, is an expert in DNA nanotechnology. Together, we wondered if we could use both D- and L-DNA to create two different sensors, or “eyes,” each matching a different type of twisted nanotube.

We did just that in the lab, and the DNA and nanotubes fit together as expected. We learned some interesting things in the process.

Molecular Chirality: Left-Handed vs. Right-Handed

Molecules don’t all behave the same. Some are “right-handed” or “left-handed,” meaning these molecules can form a mirror image of each other if you look at them next to each other. (Imagine a person’s two hands directly touching each other, except with molecules; you can’t line them up quite perfectly.) This concept is called chirality.

Other molecules are “ambidextrous”; they are identical to their mirror images. So, they are achiral.

You may be wondering why a molecule’s chirality, or lack thereof, matters. It affects how molecules interact with other molecules, depending on the task they are doing at any moment. For some tasks, left-handed molecules only want to interact with other lefties. Other times, right-handed molecules stick together. Achiral molecules are less picky and happily interact with various types of molecules.

An example of one of these “tasks” would be creating a scent. The flavor molecule limonene smells like oranges, while its mirror form smells like lemons.

Importance of Understanding and Measuring Chirality

You never know what will happen in science when we can see and measure new things. Before the microscope was invented, people didn’t know what they weren’t seeing on a microscopic level. Once microscopes were available, we learned much more about that world. We hope the same will be true for our work with molecules!

Chirality is a fundamental property of molecules in our bodies, but it was difficult to see and measure it before. Using a pair of mirror-image sensors made by DNA/nanotube hybrids, Ruojie and I found that we can tell a molecule’s chirality by comparing responses to the molecule by the two sensors. 

Now that we can see chirality more effectively, we expect to find things other people have not seen before, which may lead to exciting medical breakthroughs.

Becoming a Molecular Measurement Scientist

I studied electronics in college, but as I transitioned from adolescence into young adulthood, I became increasingly fascinated by the life sciences. This interest led me to pivot from physical sciences to biochemistry and molecular biology during my Ph.D. and postdoctoral research.

When I began working independently, I focused on using DNA — the molecule of life — to work with very small materials. I love doing research in such a captivating and versatile area of materials science.

Over time, as I have experienced the natural process of aging firsthand, my appreciation for the mystery of life and the significance of health care has deepened. Today, my drive to connect my work to the life sciences is fueled not only by intellectual curiosity but also by a desire to contribute meaningfully to public health.

Forward to the Molecular Measuring Future

While our initial efforts were successful, we don’t want to stop there. Using one pair of sensors is a good start for noticing basic chiral features. But what about complex molecules or ones that have multiple “twisty” parts?

We can broaden our idea by making many pairs of sensors, each with a different DNA sequence or nanotube structure. This is like having several pairs of “eyes,” each tuned to spot something special about a molecule.

By studying how a molecule interacts with each pair, we can build a unique “fingerprint” of its shape and then use AI to identify it. One promising goal is using this “stereo” sensor to analyze blood samples for disease.

I previously wrote a blog post about using a single-channel carbon nanotube detector to diagnose ovarian cancer more accurately than the standard procedure. Other researchers are now looking into how the technique I worked on might be used more broadly in health care to help with the earlier detection of cancer.

Now, the dual or “stereo” version — which senses the chirality of biomolecules more clearly — should do even better at spotting signs of cancer. I hope this research can detect other health conditions, too.

Turning an idea into a real technology requires a concerted effort from a community of collaborators. My colleagues at NIST and I are working on the materials and measurement tools that will help others develop these sensors.

There are many challenges, but we are confident because we’re building on what evolution figured out long ago: Having two sense organs can be better than one. Now, we’re using that age-old strategy to explore the world of molecules.