A team of American and Chinese researchers have developed a new way to significantly boost the effectiveness of photodynamic therapy in fighting cancer. The traditional technique involves injecting light sensitive drugs that are activated only when illuminated with a certain wavelength of light. For accurate targeting of tumors, the light is aimed directly at neoplastic tissue so that the drug particles coming through the tumors release singlet oxygen that kills live cells around them. While effective in some many instances, the technique has a major limitation because the frequency of light needed to activate photodynamic therapy drugs doesn’t penetrate living tissue very well, so deeply set tumors are impossible to attack this way. The new research uses so called “upconverting nanoparticles” (UCNPs) as a light converter and repeater to activate photodynamic cancer drugs much deeper in the body than ever before.
The UCNPs, which are coated with calcium fluoride and doped with ytterbium, are introduced into the body along with the light sensitive drug. The nanoparticles themselves are energized by an external 980 nm near-infrared light source and in turn emit visible red light that activates the nearby drug particles. Because near-infrared light penetrates the body’s tissues considerably deeper than visible red light, the photodynamic therapy can be used in a wider set of applications