In a groundbreaking discovery made at the Sorocaba campus of the Federal University of São Carlos (UFSCar) in Brazil, researchers have unlocked a new tool for advancing medical and environmental science. By identifying and isolating the gene encoding a firefly enzyme, they have developed an innovative biosensor capable of detecting pH fluctuations in mammalian cells. This discovery could lead to significant strides in disease research, drug toxicity testing, and much more.
The luciferase enzyme, originally found in the bioluminescent firefly species Amydetes vivianii, undergoes a dramatic color change—from bluish-green to yellow and red—when the acidity within fibroblast cells decreases. Fibroblasts, the most prevalent cell type in connective tissue, are essential for maintaining the structural framework of tissues. This enzyme’s ability to provide an accurate and stable light signal in response to pH changes opens up new possibilities for researchers. Unlike other luciferases, which had previously been tested by the group, the enzyme from Amydetes vivianii provides a far more intense, stable, and easily detectable glow. This work, published in the prestigious journal Biosensors, represents a major leap forward in the study of cellular processes and disease mechanisms.
The Power of Luciferase: From Fireflies to Cellular Insights
Luciferases are enzymes responsible for the mesmerizing glow emitted by bioluminescent organisms like fireflies, certain fungi, and deep-sea organisms. These enzymes catalyze the oxidation of a compound called luciferin, resulting in the production of light. The luciferase from Amydetes vivianii, which was first discovered in 2006 by Vadim Viviani, a professor and researcher at UFSCar, exhibits an extraordinary ability to emit light with significant variation in color and intensity in response to changes in pH. Since its cloning in 2011, Viviani and his team have been exploring its potential applications, ultimately leading to the creation of the pH-sensitive biosensor.
The ability to detect pH changes is critical because pH levels inside cells play an essential role in various cellular processes. Fluctuations in pH can signal shifts in homeostasis, cell proliferation, apoptosis (programmed cell death), and other vital processes. As Vanessa Bevilaqua, the first author of the paper and researcher at the School of Medical and Health Sciences of the Pontifical Catholic University of São Paulo (PUC-SP), explains: “Our technique has the potential to study diseases or drug toxicity, for example.”
By studying pH shifts in mammalian cells, scientists could gain insights into a variety of biological phenomena, ranging from how cells respond to stress to how they react to drug treatments. This tool could provide an invaluable method for monitoring these processes in real time, without the need for external lighting or fluorescent dyes—two common requirements in traditional cell studies.
The Technology Behind the Breakthrough
Unlike other luciferases tested by the team, the enzyme from Amydetes vivianii exhibits a wider range of light color changes when exposed to varying pH levels, even at 36°C, the standard temperature for mammalian cell activity. Many of the luciferases previously available produced a reddish light that did not respond sensitively to pH shifts. The Amydetes luciferase, on the other hand, offers a more stable and stronger bioluminescent signal. This unique combination of properties has allowed for more precise monitoring of pH levels in mammalian cells.
What sets this biosensor apart from others is not only its stability and intensity but also its non-toxic nature and its independence from external light sources. Traditional fluorescence-based techniques often require external light to excite molecules and induce them to emit light, but this new luciferase works without that, making it an incredibly valuable tool for long-term and in vivo studies.
Luciferase-based biosensors are especially exciting for researchers because of their simplicity and effectiveness. In their experiments, the UFSCar research group showed that the enzyme’s emitted light was bright enough to be captured even with a standard smartphone camera. The bioluminescence remained strong for the first 30 minutes, gradually fading over the course of the next 12 hours. Though it diminished in intensity, the light continued to be detectable with advanced photodetection equipment. The persistent glow, combined with its color shift, gives researchers a powerful tool for continuous monitoring of cellular conditions.
Applications in Drug Development and Disease Monitoring
The potential applications of this technology are vast. By monitoring changes in pH within cells, researchers can study cellular stress and its role in diseases such as cancer, metabolic disorders, and neurodegenerative diseases. The ability to track subtle shifts in pH could also help in assessing how cells respond to drugs or treatments, making it an invaluable tool in the pharmaceutical industry for toxicity testing and drug development.
Viviani highlights the significance of this discovery for drug research, stating, “It’s possible to use the color of the light to indicate the pH inside cells, including human cells, and infer whether there’s cellular stress or some other effect related to acidity.” The ability to detect cellular stress is a critical factor in understanding how a potential drug affects living cells, making this biosensor a promising tool for early-stage drug screening and toxicity evaluation.
Furthermore, this technology could be applied in cancer research. Cancer cells often exhibit altered pH levels, which can affect their growth and proliferation. By monitoring pH changes in cancer cells, researchers could gain a better understanding of how these cells behave under different conditions, providing crucial information for the development of more targeted and effective treatments.
Bridging the Gap: From Fireflies to Cutting-Edge Medical Technology
The work carried out at UFSCar and PUC-SP represents not only a technical achievement but also an example of how the natural world can inspire innovative solutions to some of science’s most pressing problems. The discovery and use of the Amydetes vivianii luciferase mark a significant advancement in the field of bioluminescence and its application to cell biology. Moreover, this research is a shining example of the scientific capabilities within Brazil, with Viviani’s laboratory making remarkable strides in bioluminescent research and bioimaging.
Beyond its immediate applications in pH sensing, this breakthrough opens up exciting possibilities for a wide range of bioassays. From drug and cosmetic toxicity testing to studying the effects of biomaterials on human cells, the potential uses of this technology are vast. Furthermore, the researchers’ earlier work in developing luciferase-based assays for COVID-19 detection demonstrates the broader utility of these bioluminescent technologies, not just for cell biology but also for diagnostic purposes in medicine and environmental monitoring.
The Future of Bioluminescence in Medicine and Beyond
The implications of this discovery are not limited to academia. As researchers and companies explore more ways to use bioluminescence, they will likely uncover even more applications for this technology, ranging from environmental monitoring to personalized medicine. With their unique ability to produce a stable, easily detectable light signal, luciferase enzymes from bioluminescent organisms are becoming increasingly valuable tools for studying complex biological processes.
Looking ahead, Viviani’s lab, equipped with its state-of-the-art bioluminescence infrastructure, is well-positioned to continue exploring these applications. With a collection of luciferases from over three decades of research, much of it focused on Brazilian insects, Viviani and his team are poised to make further discoveries that could push the boundaries of bioimaging, environmental sensing, and disease research.
As Bevilaqua succinctly concludes, “With this development, we’ve opened up a range of possibilities, from bioassays for drug and cosmetic toxicity to the effect of biomaterials on human cells, and even new ways of studying cancer cells.” The future is indeed bright for bioluminescent technologies, and this research represents just the beginning of their potential.
In a world increasingly driven by technological innovation, the simple but extraordinary glow of a firefly has sparked a new era of scientific discovery. With each flicker of light, a new possibility emerges in the quest to understand and improve the health of both people and the planet.
Reference: Vanessa R. Bevilaqua et al, Selection and Engineering of Novel Brighter Bioluminescent Reporter Gene and Color- Tuning Luciferase for pH-Sensing in Mammalian Cells, Biosensors (2025). DOI: 10.3390/bios15010018