Effect of mouse skin autofluorescence on the measurement of photosensitizer fluorescence

<strong>Background: </strong>Mouse model is a unique tool for preclinical evaluation of photosensitizing drugs for their potential applications in photodynamic therapy (PDT). The fluorescent property of photosensitizer provides a useful means for in situ measurement of photosensitizer distribution. However, the autofluorescence of mouse tissues might potentially affect in situ photosensitizer fluorescence measurement. <strong>Objectives: </strong>The aim of this study was to evaluate the autofluorescence in lab mice and its influence on the in situ measurement of photosensitizer fluorescence. <strong>Materials and Materials and methods: </strong>ICR mice, commonly used lab animal model, were used. Mice were fed with regular diet and clean water. Domestically produced photosensitizing drug Hemoporfin&#174; was used as a model sensitizer. Costume-built fluorescence imaging and spectroscope systems were used for fluorescence examination under the excitation wavelength of 400 &plusmn; 5 nm, generated from a laser or LED panel. In situ fluorescence was examined before and after i.v. injection of Hemoporfin&#174;. <strong>Results: </strong>Epifluorescence imaging examination showed yellowish and reddish autofluorescence fluorescence in the mouth, nose, paws and tail areas. The absorption and emission spectra of mouse tissue overlaid to some degrees with that of Hemoporfin&#174;. In situ fluorescence examination of ICR mice showed significant influence of autofluorescence on the spectral and intensity measurement of Hemoporfin&#174; fluorescence. Such influence might be eliminated by post-measurement spectral correction algorithms. Conclusions: The autofluorescence in mouse tissues poses a significant influence on the in situ measurement of fluorescence emission of Hemoporfin&#174;. Careful postmeasurement spectral correction is needed for accurately measuring photosensitizer fluorescence.