Light-activated ‘quantum killers’ could offer an alternative to antibiotics.
With antibiotic resistance on the rise, scientists are looking for alternative ways to ward off bacterial infections. A new antibacterial strategy using quantum dots made of graphene could take antibiotics completely out of the equation.
Under low-intensity blue light, the quantum dots were able to eliminate more than 99.9% of… Staphylococcus aureus and Escherichia coli Bacteria, including strains resistant to multiple types of antibiotics.
Over the past three decades, they have been very few in number New antibiotics They have been discovered and approved, and most are just minor variations on existing medications. This has made the world’s population increasingly vulnerable to the rapid rise in antibiotic resistance.
“The World Health Organization has warned of an impending post-antibiotic era, in which even minor infections and ordinary bacterial infections could be fatal,” wrote Sedat Nizamoglu, a professor at Koc University in Istanbul. “This phenomenon is a direct result of the increasing prevalence of antibiotic resistance among bacteria.”
In the face of this worsening crisis, Nizamoglu and his colleagues decided to take a different approach. Instead of searching for new antibiotics, they turned to a quantum-based solution to fight antibiotic-resistant bacteria.
Quantum killers
Quantum dots are structures so small — only a few tens of atoms across — that they are able to trap electrons inside them. This allows them to absorb and emit light at very specific wavelengths, making quantum dots popular across a wide range of applications including displays, solar panels and quantum computers.
In this case, the light emitted by the quantum dots reacts with oxygen to form highly reactive molecules that are toxic to bacteria. These molecules, known as reactive oxygen species, damage the cell wall that protects the bacteria and disable their antioxidant defenses, making them effective against a wide range of bacteria.
While the idea of using quantum dots to kill bacteria is not entirely new, previous attempts have faced some major limitations. The big drawback is that quantum dots are often made of heavy metals like cadmium or lead, making them toxic to humans. To adapt them to medical applications, researchers made antibacterial quantum dots using graphene, a carbon material that is harmless to us. Another challenge is that in previous studies, quantum dots were not able to kill large amounts of bacteria, even when activated with high-intensity light.
Through a simple chemical modification, Nizamoglu and his team were able to significantly increase the amount of light quantum dots emitted compared to the amount of light they first absorbed. This increased their effectiveness by more than 20 times, making quantum dots effective at much lower concentrations.
In fact, experiments on mouse cells have shown that this quantitative approach can kill Staphylococcus aureus and Escherichia coli bacteria at the lowest concentration reported to date for any light-activated quantum dots.
Antibacterial coatings
In liquid form, these quantum dots can be used in creams, gels or wound dressings to prevent and treat skin infections. Scientists have also explored coating medical implants with quantum dots to give them antibacterial properties, as these devices are often prone to causing bacterial infections.
“In particular, devices that are constantly exposed to a patient’s biogenic microbes, such as dental implants, catheters, and wound dressings, are among the applications at risk of infection and could greatly benefit from a germicidal implant coating,” Nizamoglu said.
His team has developed thin films containing five layers of quantum dots that can be used to cover implants and other medical devices. The resulting material was extremely stable and able to eliminate more than 99.9% of harmful substances Staphylococcus aureus and Escherichia coli Bacteria under low-intensity blue light, including strains of both types of bacteria that were resistant to multiple antibiotics.
More work will be needed to test this antibacterial strategy in both animals and humans before they can join the fight against antibiotic resistance. Because graphene is a stable, easy-to-manufacture, and cheap material, scientists are confident that these quantum dots could one day offer an effective and accessible alternative to antibiotics.
Reference: Muhammad Hassanein et al., Ultra-effective photoprotective antibacterial activity via carboxylate graphene quantum dots and filmsAdvanced Functional Materials (2025). doi: 10.1002/adfm.202421537
Featured Image: “Graphene Test” by thekirbster via Flickr, CCP 2.0
