Modern Optics and Spectroscopy Seminar

Photodynamic therapy (PDT) naturally lends itself to the use of optical methods for predicting and monitoring a number of quantities that are relevant to the molecular, cellular and tissue response to treatment. Fluorescence imaging and spectroscopy report the intracellular, intratumoral and whole organism distributions of the photosensitizer. Fluorescent photoproduct formation and irreversible sensitizer photobleaching during irradiation may be related to dose deposition in useful ways. At the cellular level, confocal fluorescence anisotropy images suggest that at least one photosensitizer is highly oriented in the nuclear envelope. In multicell aggregates of tumor cells subjected to PDT, confocal fluorescence imaging reports a therapy-induced reduction in light scattering. These scattering changes are correlated with dramatic changes in mitochondrial morphology observed under electron microscopy. Finally, the PDT induction of the stress protein hsp70 is observed in intact cells and in spheroids through a GFP reporter construct.