While UV light can reduce the spread of tuberculosis, UV radiation unfortunately targets both nucleic acids and proteins, killing both the viral particles and healthy mammalian cells. But researchers at Arizona State University (Tempe, AZ), Washington University School of Medicine (St. Louis, MO), and Johns Hopkins (Baltimore, MD) have discovered that another photonic approach—a near-IR ultrashort pulsed, subpicosecond fiber laser—can be used to selectively kill viruses.

By using an appropriate laser power density, the near-IR fiber laser targets only the weak links on the protein shells of viral particles. The ultrashort pulse excites the vibrational modes on the protective shells to high energy states, breaking off the weak links on the shell through impulsive stimulated Raman scattering. Once these protein shells are damaged, the viral particles are inactivated, leaving sensitive particles like human Jurkat T cells, human red blood cells, and mouse dendritic cells unharmed. A 776 nm fiber laser with a laser power density of 1 GW/cm² is powerful enough to inactivate a virus, while 10 GW/cm² can kill mammalian cells, meaning that the right laser power density is critical for successful viral inactivation without harming desirable cells. The method is now being studied for clinical treatment of blood-borne diseases like HIV and for disinfecting viral pathogens in blood products. Contact Kong-Thon Tsen at tsen@asu.edu.

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