Chinese researchers designed titanium dioxide crystals with surface defects that, under light, convert dissolved oxygen into singlet oxygen that shreds DNA left behind by bacteria.

Killing bacteria in water is something treatment plants have done for more than a century, with chlorine, ozone and ultraviolet light. But in an era of growing antibiotic resistance, killing the bacteria may not be enough. When resistant microbes die, the genes that made them resistant can survive in the water, ready to be picked up by other bacteria.

Researchers in China have developed a way to tackle that leftover genetic material. In a study published in Chem Catalysis, they describe titanium dioxide crystals that use light and the oxygen already dissolved in water to destroy DNA.

“Unlike conventional disinfection approaches that may require continuous addition of chemical oxidants, this system uses oxygen naturally available in the environment to disinfect water,” said co-author Xinjian Shi of Henan University.

Genes that outlive their hosts

Antibiotic resistance is one of the most serious threats in global health. A major analysis published in 2022 estimated that bacterial infections resistant to antibiotics were directly responsible for about 1.27 million deaths worldwide in 2019. Resistance spreads not only when resistant bacteria multiply but also when bacteria share resistance genes with one another.

The same analysis estimated that resistant infections played a role in nearly 5 million deaths that year. Health authorities including the World Health Organization have warned that without new drugs and better stewardship, routine surgery, cancer treatment and childbirth could become far riskier as common infections grow harder to treat.

One way bacteria share genes is by absorbing free-floating DNA from their surroundings, a process called transformation. That makes DNA released by dead bacteria a lingering hazard. Wastewater treatment plants, where bacteria from homes, hospitals and farms mix together, are widely regarded as hotspots for the exchange of resistance genes.

“The persistence of this genetic material is an environmental concern because extracellular DNA can be taken up by other microorganisms, potentially leading to the spread of antibiotic resistance,” said co-author Boxia Liu of North Minzu University.

Disinfection methods such as intense ultraviolet treatment can kill bacteria efficiently but may leave much of their DNA behind, according to the release.

A reactive form of oxygen

The new approach relies on photocatalysis, in which a material uses light energy to drive chemical reactions. Titanium dioxide is the best-known photocatalyst. Researchers in Japan showed in the early 1970s that it could use light to split water, and it is now used in self-cleaning glass and coatings, as well as being a common white pigment in paints and sunscreens.

The oxygen dissolved in water normally exists in a relatively unreactive form known as triplet oxygen. With an input of energy, it can be converted into singlet oxygen, a much more reactive form that readily attacks other molecules. The challenge is to produce singlet oxygen efficiently and selectively, rather than a mix of reactive species.

The team designed titanium dioxide crystals with deliberate surface defects called oxygen vacancies, gaps in the crystal where oxygen atoms would normally sit. Under light, these defects quickly convert triplet oxygen into singlet oxygen. The release describes this as a fast reaction but gives no measured values.

The paper’s title also refers to facet engineering. Crystals can be grown so that particular faces, or facets, dominate their surface, and different facets can behave very differently in chemical reactions. Combining the right facets with the right defects is one way chemists try to steer a catalyst toward a single, desired product rather than a mix.

“Catalyst defects should not simply be considered as imperfections in a material structure,” said co-author Zhi Song of North Minzu University. “When properly engineered, defects can actively regulate how molecules interact with catalyst surfaces and determine the pathways through which chemical reactions proceed.”

Cutting DNA apart

Singlet oxygen pulls electrons away from the bases that make up DNA, cutting the molecule and destroying the information it carries. A gene broken into fragments can no longer be taken up and used by another bacterium.

To test the system, the researchers added DNA-related molecules to water containing the catalysts. According to the release, the catalysts fully degraded those molecules.

The approach has an appealing simplicity. Because it uses oxygen already present in water, it would not require a constant supply of added chemicals, which can be costly and can generate unwanted by-products. Chlorine disinfection, for example, can react with organic matter to form disinfection by-products that regulators limit because of potential health concerns.

Many advanced water treatment methods, known collectively as advanced oxidation processes, rely on producing highly reactive hydroxyl radicals that attack almost anything they encounter. The new system aims for a non-radical route, generating singlet oxygen selectively, which in principle could make the reaction more targeted.

Far from the treatment plant

The work is at an early stage, and the release is short on details. It does not report sample sizes, concentrations, reaction rates or any experiments with live bacteria or real wastewater. Its main claims are qualitative.

The authors hope to scale the method up, but the release says more work is needed before it could be used in real treatment plants. The environmental and human safety of the approach still needs evaluation, and practical systems would need to deliver enough light to large volumes of often murky water, a common obstacle for photocatalytic treatment. The suggestion that controlled oxygen activation might be safer than chemical dosing has also not been tested.

Still, the work targets an underappreciated part of the antibiotic resistance problem: not just the bacteria themselves, but the genetic instructions they leave behind. The research was supported by the National Natural Science Foundation of China and the Henan Provincial Natural Science Fund for Outstanding Youth.

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Notes

1. “Direct Non-Radical Oxygen Activation on Facet-Engineered Oxide Surfaces for Selective Photocatalytic Oxidation.” Chem Catalysis, 30 September 2026. DOI: 10.1016/j.checat.2026.101873.
2. Cell Press. “Fighting antibiotic-resistant bacteria with water.” EurekAlert!, 30 September 2026. https://www.eurekalert.org/news-releases/1145263.

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