Light-activated “quantum killers” could offer an alternative to antibiotics.

With antibiotic resistance on the rise, scientists have been looking for alternative ways to fend off bacterial infections. A novel 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 over 99.9% of S. aureus and E. coli bacteria, including strains resistant to multiple types of antibiotics. 

Over the past three decades, very few new antibiotics have been discovered and approved, and most are only slight variations of existing drugs. This has left the world’s population increasingly vulnerable to the rapid rise of antibiotic resistance. 

“The World Health Organization (WHO) warned about the impending ‘post-antibiotic’ era, where even minor injuries and ordinary bacterial infections may prove fatal,” writes Sedat Nizamoğlu, professor at Koç University in Istanbul. “This phenomenon is a direct consequence of the growing prevalence of antibiotic resistance among bacteria.”

Facing this growing crisis, Nizamoğlu and 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—just about a few dozen atoms wide—that they are able to trap electrons inside. This allows them to absorb and emit light at very specific wavelengths, making quantum dots popular across a wide range of applications including screen displays, solar panels, and quantum computers.  

In this case, light emitted by the quantum dots reacts with oxygen to create highly reactive molecules that are toxic to bacteria. Known as reactive oxygen species, these molecules damage the cell wall that protects bacteria and disrupt their antioxidant defenses, making them effective against a broad range of bacteria. 

While the idea of using quantum dots to kill bacteria is not entirely new, earlier attempts have faced some major limitations. A significant drawback is that quantum dots are often made of heavy metals such as cadmium or lead, which makes them toxic to humans. To adapt them for medical applications, the researchers made the antibacterial quantum dots using graphene, a carbon-based material that is harmless to us. Another challenge is that, in previous studies, quantum dots were unable to kill substantial amounts of bacteria, even when activated with high-intensity light.

With a simple chemical modification, Nizamoğlu and his team significantly increased the amount of light quantum dots emit compared to how much light they first absorbed. This increased their efficacy by more than 20 times, making the quantum dots effective at much lower concentrations. 

In fact, experiments in mouse cells showed that this quantum approach could kill S. aureus and E. coli bacteria at the lowest concentration reported to date for any light-activated quantum dots. 

Antibacterial coatings

In liquid form, these quantum dots could be used in creams, gels or wound dressings to prevent and treat skin infections. The scientists also explored coating medical implants with the quantum dots to give them antibacterial properties, as these devices are often prone to causing bacterial infections. 

“Particularly, devices continuously exposed to the patient’s microbiota, such as dental implants, catheters, and wound dressings are among applications that are at risk for infection and could majorly benefit from a bactericidal implant coating,” stated Nizamoğlu.

His team developed thin films containing five layers of quantum dots that could be used to coat implants and other medical devices. The resulting material was highly stable and able to eliminate over 99.9% of S. aureus and E. coli bacteria under low-intensity blue light, including strains from both bacteria types that were resistant to multiple antibiotics.

More work to test this antibacterial strategy both in animals and humans will be needed before they can join the fight against antibiotic resistance. Because graphene is a stable material that is easy and cheap to synthesize, the scientists are confident that these quantum dots could one day offer an effective and accessible alternative to antibiotics.

Reference: Muhammad Hassnain et al., Ultra-Effective Light-Activated Antibacterial Activity via Carboxyl Functionalized Graphene Quantum Dots and Films, Advanced Functional Materials (2025). DOI: 10.1002/adfm.202421537

Featured image: “Test Graphene” by thekirbster via Flickr, CC BY 2.0