Two-photon excited imaging of photosensitizers in tissues

Two-photon microscopy (TPM) is a non-invasive biological imaging technique that can be used to selectively image cellular activity and photosensitizer (PS) localization within highly scattering epithelial tissues at depths of approx. 200 μm with submicron resolution. The principal objective of this study was to develop a model system for understanding the impact of photodynamic therapy on cellular and extracellular matrix remodeling in biological tissues. An artificial tissue model (RAFT) composed of collagen, embedded fibroblasts, and macrophage cells has been developed for this purpose. TPM is utilized to monitor extracellular matrix remodeling following PDT by imaging collagen/elastin autofluorescence. Selective uptake of photosensitizers by specific cellular components in the matrix can also be visualized by TPM