Nanotechnology: A Gentle Introduction to the Next Big Idea

Photodynamic Therapy

Nearly every child has held up a flashlight to her hand and seen how the light passes through her hand and looks red when it comes out. This red color isn't only because of red blood. Instead, like the blue color of the sky, it arises because the amount of light that is scattered by an object depends on the wavelength of the light. Light with long wavelengths can actually pass through biological tissue without excessive scattering and, therefore, can be used to affect processes within the body.

In photodynamic therapy, a particle is placed within the body and is illuminated with light from the outside—the light could come from a laser or from a light bulb. The light is absorbed by the particle, after which several things ...