Carbon dioxide (CO₂) connects us to the natural world: what we breathe out becomes fuel for forests. But inside our own bodies, CO₂ has a secret life. It sparks chemical reactions, shapes metabolism, and may even act as a signalling molecule — and a new tool is finally letting researchers watch it glow in action.

Dr Eoin Cummins, Associate Professor in the UCD School of Medicine and Fellow, UCD Conway Institute and PhD student, Ben Reddan have shown for the first time how a newly developed chemical sensor called CarboSenR2 can detect CO₂ levels in cells.

CarboSenR2 lights up when it meets CO₂. This helps scientists see where and when CO₂ is being made inside cells and allows scientists to study how CO₂ levels change in response different stimuli such as exercise.
CO₂ is an ancient and ubiquitous physiological gas that every cell in the body is exposed to. However, until recently scientists lacked the necessary tools to study CO2 in living systems. This is despite CO2 being known to affect many cellular processes such as inflammation and wound healing.

The Cummins group have pioneered the use of a newly developed chemical sensor to measure CO2 directly in cells giving us new insights into the role of this important gas for normal physiology and in disease.
Many illnesses—like cancer, infections, and muscle problems—change how cells make energy. High levels of CO₂ in the body are seen in serious diseases such as chronic obstructive pulmonary disease (COPD), acute respiratory distress syndrome (ARDS) and cancer.

Explaining the research carried out in the Cummins group, Ben Reddan said, “CarboSenR2 is a tiny molecule that glows differently depending on how much CO₂ is around. When CO₂ levels rise, the sensor undergoes a chemical reaction and switches from green to red light. This makes it possible for us to see CO₂ inside living cells. We used the sensor in several types of cells and measured the colour changes using flow cytometry and microscopy within the core technology platforms within UCD Conway Institute and the O’Brien Centre for Science. Mitochondria are the power stations inside cells and the dye showed bright spots near mitochondria confirming that this is where lots of CO₂ is being made.
We used electrical pulses to make muscle cells ‘exercise’, which caused the dye to glow more, showing more CO₂ was being made. If we blocked mitochondria from doing their job, CO₂ production went down and the dye glowed less.
We also looked at the amount of CO₂ being made by different immune cells. Some immune cells (called M1 macrophages) make less CO₂ because they use a different kind of metabolism. The dye could tell these cell types apart which could be important when studying CO2 in disease."

Commenting on the study, Dr Cummins said, “Carbon dioxide is the ‘elephant in the room’ of human physiology. It is always present yet often invisible or ignored. This work shines a light on that elephant – letting us see and measure the CO2 produced in cells for the first time. Our hope is that a greater appreciation of the role of CO2 in biological systems will lead to innovation and discovery in this space – bringing clinical insight and new treatments for patients.”