Johns Hopkins University student Shaw-Wei David Tsen says that it was during a stroll in the park with his father that the idea was born. David, an immunology researcher in the laboratory of T.C. Wu at Hopkins' Kimmel Cancer Center, sought a new method to free isolated blood of dangerous pathogens, including the viruses HIV and hepatitis C. He says current techniques using UV irradiation and radioisotopes can leave a trail of mutated or damaged blood components, and could destroy viruses.
However, David said that his father, Kong-Thon Tsen, a laser expert at Arizona State University, had a better idea: Lasers, unlike ultrasound, can penetrate energy-absorbing water surrounding the viruses and directly vibrate the pathogen itself.
The researchers aimed a low-power laser with a pulse lasting 100 femtoseconds (10-13 second) into glass tubes containing saline-diluted viruses that infect bacteria, also known as bacteriophages. The amount of infectious virus within each cube plummeted 100- to 1000-fold after the laser treatment.
"I had to repeat the experiment several times to convince myself that the laser worked this well," says David.
He says that their laser is different from those emitting a continuous beam of visible light.
"Our laser repeatedly sends a rapid pulse of light and then relaxes, allowing the solution surrounding the virus to cool off. This significantly reduces heat damage to normal blood components," he adds.
Developing the idea that vibration wrecks a virus' outer shell, the scientists found that their low-power laser selectively destroys viruses and spares normal human cells around them, while stronger beams kill almost everything.
Prof Wu says that the technique his student developed "could potentially be used to control communicable diseases by giving infusions of laser-treated blood products."
The scientists published their results in the July 13 issue of the Journal of Physics: Condensed Matter.