Modulating Effects of Amino Acids on Low-Temperature Plasma-Induced DNA Damage
This study demonstrates that low-temperature plasma induces DNA damage through both reactive oxygen and nitrogen species and acidification, while amino acids like tryptophan, tyrosine, and methionine mitigate the radical-driven component of this damage via concentration-dependent scavenging independent of pH buffering.
Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). This is an AI-generated explanation of a preprint that has not been peer-reviewed. It is not medical advice. Do not make health decisions based on this content. Read full disclaimer
Imagine a world where invisible, electrically charged gas can heal wounds, kill bacteria, or even target cancer cells without cutting the skin. This is the promise of low-temperature plasma, a state of matter that behaves like a gas but carries enough energy to interact with living tissue. Scientists have long known that when this plasma touches water or the fluids inside our bodies, it creates a storm of highly reactive particles. These particles, born from the interaction between the gas and the liquid, are powerful enough to break apart the delicate strands of DNA, the molecule that holds our genetic instructions. If the DNA breaks, cells can die or mutate, which is useful for killing a tumor but dangerous if it happens to healthy tissue. However, the chemistry of this process is complicated. The plasma doesn't just throw reactive particles at the DNA; it also changes the acidity of the liquid it touches, making it more sour. It has been unclear whether the damage comes from the reactive particles, the sourness, or a combination of both, and whether the natural building blocks of our bodies, like amino acids, could act as a shield.
In a recent study, researchers at the University of Notre Dame set out to untangle these effects. They wanted to see if adding specific amino acids—tryptophan, tyrosine, and methionine—could protect DNA from the assault of low-temperature plasma. To do this, they took a simple, circular piece of DNA, similar to a tiny ring, and exposed it to a jet of helium plasma. They watched what happened to the DNA rings as the plasma hit them for different lengths of time. The team ran two main sets of experiments: one where the liquid was allowed to become acidic, just as it naturally would when hit by plasma, and another where they added a buffer to keep the liquid neutral, preventing the pH from dropping. This allowed them to see if the sourness of the liquid was a major cause of the damage, or if the reactive particles were doing all the work.
The results were clear. When the liquid was left to become acidic, the DNA suffered significantly more damage, with the rings breaking apart much faster than when the acidity was controlled. This confirmed that the drop in pH, caused by the plasma dissolving nitrogen oxides into the water, is a major contributor to the destruction of DNA. However, the story didn't end there. When the researchers added small amounts of the three amino acids to the mix, the DNA was protected. The rings stayed intact for longer, even as the plasma continued to bombard them. This protection happened whether the liquid was acidic or neutral, suggesting that the amino acids were doing something more than just neutralizing the sourness. In fact, the amino acids did not stop the pH from dropping; the liquid still became acidic, yet the DNA survived better.
The researchers then looked at how these amino acids worked. They suspected the amino acids were acting as scavengers, grabbing the dangerous reactive particles before those particles could reach and break the DNA. To test this, they used a chemical probe that lights up when it reacts with hydroxyl radicals, one of the most destructive particles created by the plasma. They found that when they added a known scavenger, the probe received fewer radicals, proving that the scavengers were successfully competing for the reactive particles. The three amino acids they tested behaved almost identically in their ability to protect the DNA. This makes sense because, despite having different shapes, they all react with the hydroxyl radical at nearly the same speed. The study suggests that at the low concentrations used, these amino acids protect DNA primarily by intercepting the reactive radicals, effectively taking the hit so the DNA doesn't have to.
While the amino acids offered significant protection, they could not completely stop the damage caused by the acidic environment. Even with the amino acids present, the DNA still suffered more in the acidic solution than in the neutral one. This tells us that a complete shield against plasma damage would need to address both the reactive particles and the change in acidity. The study concludes that when plasma interacts with biological fluids, the damage is a two-part problem: the chemical assault from reactive species and the physical stress from the changing pH. The presence of natural amino acids in our bodies might offer some defense against the chemical assault, but it is not a perfect shield. For future medical treatments using plasma, understanding this balance is crucial. If doctors want to use plasma to treat cancer or heal wounds, they must consider how the surrounding fluids and the molecules within them will react, ensuring that the treatment kills the target without causing unnecessary harm to the healthy tissue around it.
Drowning in papers in your field?
Get daily digests of the most novel papers matching your research keywords — with technical summaries, in your language.