Figure 4: a) Fluorescence spectra of PpIX induced by ALA and ALA-heptyl ester in WiDr cells before and after blue light exposure 400-460 nm. The excitation wavelength was 407nm. b) Fluorescence spectra of PpIX induced by ALA and ALA-heptyl ester in normal mouse skin before and after blue light exposure 400-460 nm