Quantitative assessment of cell migration in vitro is often required in fundamental and applied
research from different biomedical areas including wound repair, tumor metastasis or developmental
biology. A collection of assays has been established throughout the years like the most widely used
scratch assay or the so-called barrier assay. It is the principle of these assays to introduce a lesion into
an otherwise confluent monolayer in order to study the migration of cells from the periphery into this
artificial wound and determine the migration rate from the time necessary for wound closure. A novel
assay makes use of photosensitizers doped into a polystyrene matrix. A thin layer of this composite
material is coated on the bottom of regular cell culture ware showing perfect biocompatibility. When
adherent cells are grown on this coating, resonant excitation of the photosensitizer induces a very
local generation of 1O2, which kills the cells residing at the site of illumination. Cells outside the site
of illumination are not harmed. When excitation of the photosensitizer is conducted by microscopic
illumination, high-precision wounding in any size and geometry is available even in microfluidic
channels. Besides proof-of-concept experiments, this study gives further insight into the mechanism
of photosensitizer-mediated cell wounding.