In vitro and in vivo evaluation of the induced PDT response using a femtosecond laser

摘要

One of the limitations of PDT in the treatment of bulk tumors is the light penetration in biological tissues at the red spectrum. PDT illumination at short pulsed regime may present a higher light penetration compared to the CW regime, and potentially a higher volume of induced necrosis. The major goal of this study was an in vitro and in vivo evaluation of PDT response after illumination using a 630 nm femtosecond laser. Photogem~? in distilled water solution was illuminated either with CW or femtosecond laser under the same fluence and fluence rate parameters. Wistar rats weighting between 280 and 300 g were intravenously photosensitized with Photogem. Thirty minutes after drug injection, the normal liver was irradiated either with the CW or the femtosecond laser (fluence: 150 J/cm~2). The in vitro results showed that, under the same conditions, the degradation rate evaluated via fluorescence spectroscopy was higher under femtosecond laser irradiation. Histological analysis of the induced necrosis showed that there was a significant higher depth of necrosis when the femtosecond laser was used. Based on these results, femtosecond lasers seem to be an alternative in PDT applications, improving results for the treatment of lesions for which a larger light penetration is required.