Researchers detected ultraweak light emitted by living mice and plant leaves, opening new possibilities for studying cellular health without invasive procedures.
Researchers have captured one of the faintest biological signals ever observed, extremely faint natural light emitted by living cells that drops sharply after death in mice. Scientists from the University of Calgary and the National Research Council of Canada found that this ultraweak photon emission (UPE) is closely linked to biological activity and may one day provide a non-invasive way to study tissue health. Although the experiments were conducted in mice and plant leaves, the findings offer fresh insight into how living cells function and respond to stress.(1✔ ✔Trusted Source
Imaging Ultraweak Photon Emission from Living and Dead Mice and from Plants under StressThe phenomenon of biological ultraweak photon emission (UPE)
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The researchers also found that injured plant leaves emitted stronger light signals than healthy leaves, supporting the idea that reactive oxygen species (ROS) produced during cellular stress play an important role in generating this natural glow.
Although this research was conducted in animals and plants, the same fundamental biological processes that produce reactive oxygen species also occur in human cells. Researchers say the findings could help develop future non-invasive techniques to study tissue health, monitor cellular stress, and better understand disease processes in humans. However, the technology is still in the research stage and is not yet ready for clinical use or disease diagnosis.
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Scientists Detect Faint Light from Living Cells
The idea that living organisms produce tiny amounts of light has fascinated scientists for decades. However, this phenomenon should not be confused with unsupported claims about human auras or paranormal energy fields.
Known as ultraweak photon emission (UPE), these extremely faint light signals are naturally produced during normal biological processes. Because the emitted light is millions of times weaker than ordinary visible light and easily overwhelmed by surrounding light and body heat, detecting it across an entire living organism has remained a major scientific challenge.
Using highly sensitive electron-multiplying charge-coupled device (EMCCD) and charge-coupled device (CCD) cameras, physicist Vahid Salari and colleagues successfully detected these ultraweak light emissions from living mice and compared them with measurements taken after death. The researchers also observed similar emissions from plant leaves, providing direct evidence that this faint glow is associated with living biological activity.
The findings build on previous research showing that spontaneous light emissions between 200 and 1,000 nanometers can occur in living tissues, including cow heart tissue and bacterial colonies, although the signals are far too weak to be seen with the naked eye.
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What Causes Living Cells to Emit Faint Light?
Scientists believe the faint glow is largely produced by reactive oxygen species (ROS), molecules that form naturally when cells undergo normal metabolism or experience stress from heat, toxins, pathogens, or nutrient shortages.
For example, molecules such as hydrogen peroxide can trigger chemical reactions involving fats and proteins that excite electrons within cells. As these electrons return to their normal energy state, they release tiny packets of visible light known as photons.
Because these reactions occur continuously inside living cells, researchers believe that measuring ultraweak photon emissions could eventually provide valuable information about cellular stress, tissue function, and biological activity without physically disturbing the tissue. However, further studies are needed before this approach can be applied in human healthcare.
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How Researchers Measured Ultraweak Light in Mice
To determine whether ultraweak photon emission (UPE) could be detected across an entire living organism rather than only in isolated tissues, the researchers used highly sensitive electron-multiplying charge-coupled device (EMCCD) and charge-coupled device (CCD) cameras to measure the faint light emitted by whole mice.
Four immobilized mice were individually placed inside a completely dark chamber and imaged for one hour while alive. The mice were then euthanized and imaged for another hour under the same conditions. To ensure that body heat did not influence the measurements, the animals were maintained at normal body temperature throughout the imaging period.
The researchers detected individual visible-light photons from the mice both before and after death. However, the number of ultraweak photon emissions decreased significantly after death, providing direct physical evidence that these faint light signals are closely associated with living biological activity rather than body temperature alone.
Plant Study Supports the Same Biological Process
To investigate whether the same phenomenon occurs in plants, the researchers examined leaves from Arabidopsis thaliana and Heptapleurum arboricola. The leaves were exposed to physical injury and chemical treatments to increase cellular stress before their light emissions were monitored.
The injured areas consistently emitted stronger ultraweak photon emissions than healthy parts of the leaves throughout the 16-hour imaging period. These findings support the theory that reactive oxygen species (ROS) generated during cellular stress are an important source of the faint light emitted by living organisms.
The researchers reported, “Our results show that the injury parts in all leaves were significantly brighter than the uninjured parts of the leaves during all 16 hours of imaging.”
Why This Discovery Could Change Future Health Research
Although this study was carried out in mice and plants, the biological processes responsible for producing reactive oxygen species are common to many living organisms, including humans. This means the findings could help scientists better understand how human cells respond to normal metabolism, stress, injury, and disease.
If future studies confirm that ultraweak photon emissions accurately reflect cellular health, researchers may eventually develop completely non-invasive methods to monitor tissue stress, study biological activity, and evaluate how cells respond to disease or treatment. Such technology could become a valuable research tool and, after further validation, may contribute to future clinical applications.
The researchers emphasize that these findings should not be interpreted as evidence that the technique is ready to diagnose diseases or assess health in humans. Additional studies are needed to determine whether similar measurements can be reliably used in people and how they might contribute to future medical research.
By revealing that living cells produce measurable ultraweak light linked to biological activity, this study expands our understanding of one of nature’s most subtle biological signals. While its clinical applications remain a future goal, the discovery provides a promising foundation for developing innovative, non-invasive tools that could transform biomedical research and deepen our understanding of human health.
References:
- Salari V, et al. Ultraweak Photon Emission from Living Biological Systems. The Journal of Physical Chemistry Letters. 2025. https://doi.org/10.1021/acs.jpclett.4c03546
Source- University of Calgary; The Journal of Physical Chemistry Letters