Light-Based Approach Pushes PDT Deeper into Body Tissue

Photodynamic therapy (PDT) for years has proven to be an effective cancer treatment, although only on easily accessible tumors such as in oral and skin cancers.

A new technique — developed by a team from the University at Buffalo in collaboration with researchers at Shenzhen University and Korea University — uses NIR light to push such treatment deeper into body tissue than ever before.

In current photodynamic therapy, cancer cells are injected with a drug containing a photosensitizing agent activated by visible light — but only on a superficial level.

A new approach to PDT penetrates deeper into body tissue and cancer cells (shown here), effectively killing more types of cancer than was possible before. Courtesy of the University at Buffalo.

Under the new approach, NIR beams — upon penetrating deep into body tissue — are converted into visible light through second-harmonic generation.

“We expect this will vastly expand the applications for an effective cancer phototherapy that’s already in use,” said team member Dr. Tymish Ohulchanskyy, a professor and deputy director of photomedicine at the UB Institute for Lasers, Photonics and Biophotonics (ILPB).

Essentially, the tumors’ natural environment is used to tune the light into the necessary wavelengths. Natural proteins and lipids within the cells interact with NIR laser light, the researchers said, which changes to visible light through four-wave mixing. Visible light can then be generated in tumors deep inside the body, activating the drugs to destroy the tumors.

A less-invasive, more-targeted alternative to surgery, PDT does not have long-term side effects, said lead researcher Dr. Paras Prasad, a professor and executive director of ILPB.

“With our approach, PDT is enriched to provide another tool that doctors can use to alleviate the pain of millions of people suffering from cancer,” he said.

The UB team has applied for a patent for this new technique.

The work was funded by a grant from the U.S. Air Force Office of Scientific Research and published in Nature Photonics (doi: 10.1038/nphoton.2014.90).

For more information, visit www.buffalo.edu.