A father-son research team has found a way to zap viruses out of blood with a low-power laser beam in pulses lasting tiny fractions of a second. It holds promise for disinfecting blood for transfusions. Johns Hopkins University student Shaw-Wei David Tsen, an immunology researcher, was looking for a method to rid isolated blood of dangerous pathogens, including HIV and hepatitis C. He says current techniques using UV irradiation and radioisotopes leave a trail of mutated and damaged blood components.

Using ultrasonic vibrations to destroy viruses seemed a possibility. But his father, Kong-Thon Tsen at Arizona State University, suggested that lasers do a better job of getting through the energy-absorbing water surrounding the viruses and vibrating the pathogen.

To test the idea, the team aimed a low-power laser with a pulse lasting 100 femtoseconds (10^-13 sec) into glass tubes containing saline-diluted viruses that infect bacteria. “Our laser repeatedly sends a rapid pulse of light and then relaxes, letting the solution surrounding the virus cool off,” says David Tsen. “This significantly reduces heat damage to normal blood components.” It also sent the percentage of infectious virus in each tube to 0.1 to 1% of pretreatment levels.

The scientists found that their low-power laser selectively destroys viruses and spares normal human cells around them, while a stronger beam kills almost everything. The Tsens speculate that laser vibrations could destroy drug-resistant and sensitive viruses.