Two-photon excitation studies of m-THPC photosensitizer and photodynamic activity in an epithelial cell line

SummaryA femtosecond laser delivering pulses of wavelength 800 nm and 124 fs duration at rates of 1 kHz has been used to investigate the two-photon excited fluorescence in the photosensitizer m-THPC. The scaling of fluorescence amplitude with laser power and fluorescence sidelight imaging are found to support a predominantly two-photon excitation mechanism. A value for the two-photon cross-section of δ = 1.8 × 10−57 m4 s is derived by comparing the fluorescence signals excited by wavelengths of 800 and 400 nm. Preliminary results demonstrating the two-photon induced PDT activity of m-THPC in an epithelial cell line are also reported.