Detection of Reactive Oxygen Species during Photodynamic Therapy

Abstract

Reactive oxygen species (ROS), also known as oxidants, are often utilized in a variety of therapies, such as in photodynamic therapy (PDT) which is an emergent cancer and tumor therapy. The production of ROS in cancerous cells induces oxidative stress, promoting apoptotic cell death. Here we utilize fluorescent molecular sensors to quantify the generation of ROS by a photosensitizer and a room-temperature plasma source.  We observe a linear increase in the production of ROS in solution, as a function of light irradiation dose, as measured by the intensity of fluorescence of sensor molecules. The same trend was also observed using the plasma source. It was also observed that in both experiments the signal saturated after prolonged irradiation time. This can be attributed to finite concentration of sensor molecules present in the solution. While ROS production can continue to increase linearly due to further irradiation, the increase in ROS can no longer be detected after prolonged irradiation time due to the limited number of sensors in the sample.