Viruses lurking in biological samples could be killed off with an intense pulse of visible light, new research shows.

Scientists in the US say the technique seems to have significant advantages over alternative methods, including use of UV irradiation or microwaves, as it kills viruses more effectively and safely.

The technique destroys a virus with a pulse of light from a low-power laser. The pulse produces mechanical vibrations in the virus shell, or capsid, irreversibly damaging and disintegrating it, and so "deactivating" the virus for good. The technique might be used to kill HIV, as well as hepatitis C, say the researchers involved.

Traditional methods of destroying viruses, such as UV irradiation, can cause mutations, which eventually make the micro-organisms resistant. UV light can also damage the DNA of surrounding healthy cells.

Scientists have also tried using microwaves to kill viruses but this is even less promising since the water in and around a micro-organism strongly absorbs this frequency of light. Most of the energy from the microwave radiation is absorbed by the water and does not even reach the virus itself.

Human cells undamaged

Kong-Thon Tsen of Arizona State University, and colleagues at Johns Hopkins School of Medicine, and the Uniformed Services University of The Health Sciences, all in the US, found that visible light can overcome this problem.

The researchers applied pulses of purple-coloured light lasting just 100 femtoseconds (10^-15 seconds) to viruses called M13 bacteriophages. It takes just a single pulse to destroy the viruses completely, say the researchers.

The "power density" of the laser is just 5 microjoules per square centimetre, which is low enough to leave surrounding human cells and tissue undamaged, but high enough to produce large-amplitude vibrations in a virus's capsid. It is also too low to cause genetic mutations, meaning the virus will not build up resistant to the treatment over time.

Disinfecting blood

Tsen told New Scientist that the technique could be used to disinfect blood or other biological samples in hospitals.

"In addition, we believe that the method may be especially important in designing novel treatments for blood-borne viral diseases," he said. "For example blood dialysis allows us to irradiate a patient's blood outside the body and potentially cleanse it of infectious virus particles before reintroducing it into the patient. In this way, we could reduce mortality associated with diseases like hepatitis C and AIDS."

The team now plans to test the efficacy of its technique in killing a wide range of deadly viruses, including HIV and hepatitis C. "We also plan to conduct further tests on the effects of the low-power visible laser on mammalian cells to determine any potential side effects and confirm that it selectively kills viruses," said Tsen.

Journal reference: Journal of Physics: Condensed Matter (19 322102)