In the lab of Vladimir Birman, an associate professor of chemistry, green is good. Deep-green colors absorb and emit light in the near infrared. Birman is interested in such dyes for a simple reason: they make it possible to see tissues and processes in the body without potentially harmful X-ray radiation or expensive MRIs. 

As Birman described at the 2026 Arts & Sciences Research Innovation Showcase, his lab is now teeming with FROGs, which is a backronym he came up with for “Fiercely Radiant Oxonol Green”. Living up to the name, these new compounds look intensely green to the naked eye and shine bright under near-infrared light. 

Birman and his team created FROGs in a quest to discover a new stable, non-toxic dye that could be used for medical imaging. In theory, such a dye could be injected into tissues or the bloodstream. If a doctor shined near-infrared light at the body, the dyes would glow, illuminating the body from within. 

Unlike regular visible light from a lamp or a flashlight, the long wavelengths of near-infrared light penetrate through tissues, making every part of the body potentially within view. “Body tissues are essentially transparent to near-infrared light,” Birman said. “You can see the results in real time, which makes it possible to conduct fluorescence-guided surgery.”

The first batch of FROGs, detailed in the journal Chemical and Biomedical Imaging, already shows great promise. “The FROGs we created shone even brighter than indocyanine green (ICG), the only near-infrared dye that’s currently approved for human imaging,” Birman said. 

The search for FROGs started with help from a Seeding Projects for Enabling Excellence & Distinction (SPEED) grant in 2023. The Arts & Sciences funding program was created to stimulate innovative work that leads to significant outcomes in research, scholarship, and creative practice. 

Although Birman and his team previously thought a specific chemical approach might create bright green compounds, the color appeared at an unexpected point of the process. “The discovery was a mix of good intentions and serendipity,” he said. 

Tests by Birman’s long-time collaborator Mikhail Berezin, an affiliated professor of chemistry and an associate professor of radiology at WashU Medicine, showed that the dye was well-tolerated by mice, an encouraging sign that FROGs or their close relatives could someday be safely used in humans. 

“Mikhail had the original idea to search for a new dye,” Birman said. “We applied for the SPEED grant together. His knowledge of bioimaging fits well with my ability to synthesize molecules.”

ICG, the existing near-infrared dye used in hospitals around the world, is also well-tolerated, but it has some limitations, Birman said. “It’s pretty unstable, so it has to be injected continuously to get any sort of signal for bioimaging,” he said. Birman added that ICG has been around since the 1950s, which is ancient history in the rapidly changing world of medicine. 

As a next step, Birman and his team plan to modify FROGs to create a new class of compounds that can shine even brighter under near-infrared light. The acronym for the new compounds is still to be decided. 

A bright, stable, and well-tolerated dye could give doctors a much-needed update to their ability to visualize tissues, Birman said. “We think FROGs will provide a safe and effective alternative to ICG,” Birman said. “It’s important to have different options.”