A 70-nanometer diamond particle—smaller than a red blood cell—was injected into a living yeast cell. Inside the cell, the diamond did more than simply remain there. It acted as a sensor, capturing magnetic signals from molecules that have long been extremely difficult to measure directly. This is the essence of research involving drg. Aryan Morita, M.Sc., Ph.D., a lecturer in the Department of Dental Biomedical Sciences at Universitas Gadjah Mada, together with a team from the University of Groningen, the Netherlands, and École Polytechnique Fédérale de Lausanne (EPFL), Switzerland. The research, which has been published in a scientific paper, represents the first use of diamond magnetometry to directly and in real time measure free radicals in living cells.
Tiny Enemies That Are Difficult to Detect
Free radicals are unstable molecules produced by the body as part of normal metabolic processes. In controlled amounts, they play important roles: they help facilitate communication between cells, fight pathogens, and are even involved in the mechanisms of action of many drugs. However, when present in excess, they damage DNA, proteins, and cell membranes—a process believed to be one of the major mechanisms underlying aging.
The problem is that free radicals are extremely difficult to measure. They occur at very low concentrations, ranging from nanomolar to micromolar levels, and have extremely short lifespans before reacting with other molecules. Conventional techniques, such as organic fluorescent dyes, can detect only the history of free-radical exposure rather than the condition occurring at that very moment. Other techniques, such as conventional MRI, require billions of atoms to generate a detectable signal, making their resolution insufficient for observing what happens inside a single cell.
“We use a new technique called diamond magnetometry. Through quantum effects, defects in the diamond convert magnetic resonance signals into optical signals. This is the first time this technique has been used to measure free radicals in living cells.” — drg. Aryan Morita, M.Sc., Ph.D., Department of Dental Biomedical Sciences, FKG UGM
Nanodiamonds as Quantum Sensors
The research team harnessed a quantum-physics phenomenon found in structural defects within diamond crystals known as nitrogen vacancy (NV) centers. These defects are highly sensitive to surrounding magnetic fields, including the weak magnetic signals generated by free radicals.
Here is how the system works: fluorescent nanodiamonds (FNDs) measuring 70 nm in diameter are introduced into living yeast cells. The cells are then observed using a custom-built confocal microscopy setup. By directing green laser pulses at the diamonds and measuring the relaxation time of the NV centers, known as the T1 value, the researchers can determine how many free radicals are present around the diamond at that moment. The shorter the T1 value, the greater the free-radical burden in the cell.
The advantage of this method over conventional techniques is significant. Measurements can be performed on the same cell, at the same location, before and after a biological intervention. There is no need to compare different cells as controls. The diamonds also do not undergo photobleaching like organic fluorescent dyes, allowing them to be used for long-term observation.
Four Yeast Strains, Four Metabolic Stories
The study used four strains of the yeast Saccharomyces cerevisiae: a normal wild-type strain and three mutants with different metabolic characteristics. The sod1Δ mutant lacks the gene encoding the enzyme superoxide dismutase, making it less capable of neutralizing free radicals. The tor1Δ and pex19Δ mutants, meanwhile, are known to have longer lifespans than normal, although the mechanisms underlying this phenomenon have not been clearly explained.
The results were quite surprising. All of the mutants showed higher free-radical burdens than the wild-type strain. The sod1Δ mutant responded to oxidative stress induced by hydrogen peroxide (H₂O₂) by producing more radicals. In contrast, tor1Δ and pex19Δ showed reduced free-radical levels after exposure to H₂O₂, indicating that these two mutants were more resistant to oxidative stress.
The most interesting finding emerged from observations of the aging process. Aged pex19Δ cells actually had a lower free-radical burden than when they were young. This provides a biological explanation that had previously been lacking for why cells with the pex19Δ mutation can live longer. Activation of superoxide dismutase in response to increased hydrogen peroxide is thought to be a key factor.
The study also demonstrated that adding the antioxidant L-ascorbic acid (vitamin C) significantly reduced the free-radical burden inside the cells. In tor1Δ and pex19Δ cells, the antioxidant was even able to suppress the increase in free radicals when the cells were exposed to chemical stress—an effect that was not observed in the wild-type or sod1Δ strains.
From Yeast Cells to the Future of Biomedicine
Yeast was not chosen arbitrarily. Many aging and stress-response processes in yeast resemble those occurring in human cells. Yeast can also undergo two forms of aging: replicative aging, associated with cell division, and chronological aging, associated with remaining in an inactive state. Both are relevant models for studying different forms of human cellular aging.
The implications of this research extend far beyond basic biology. The ability to measure free radicals directly in individual living cells, in real time, opens new possibilities for evaluating how drugs work, understanding disease mechanisms involving oxidative stress—from cardiovascular disease and cancer to immune responses—and testing the effectiveness of antioxidants at a scale that has never previously been possible.
For dentistry, where oxidative stress plays a role in the pathogenesis of conditions ranging from periodontal disease to oral mucosal lesions, quantum sensor technology of this kind holds considerable potential. The diamond traditionally associated with jewelry may now become a diagnostic tool capable of looking directly inside cells—and what it reveals could change how we understand aging itself.
Authors: Achmad Zam Zam Aghasy, DDS, M.Kes.; Hazra Alifia Muharam
Photo: Freepik