[Control of intensity of light coagulation by thermo-induced release of a fluorescent marker encapsulated in liposomes. In vivo/ex vivo preliminary study].

PURPOSE

The aim of this in-vivo/ex vivo study was to assess the possible use of temperature sensitive liposomes in an established model such as the liver as a new approach to monitor the temperature induced by a laser.

METHOD

Temperature sensitive liposomes (DSPC: DiStearoylPhophatidyl-Choline: critical temperature: 55 degrees C) loaded with carboxy-fluoresceine were prepared by the Bancham procedure. These liposomes (1 ml solution) were injected to adult male wistar rats. Two hours later, the liver was exposed and irradiated with a 100 W Nd: YAG laser (single pulse mode, pulses ranging from 100 to 260 ms, spot diameter: 4 mm). Simultaneously, the surface temperature was recorded with a infrared thermographic camera (Aga). The fluorescence emission was then measured with a fluorescent imaging system (Hamamatsu).

RESULTS

The dye was released in response to laser energy. The amount of the drug release increased linearly with increasing temperature in the range 42 to 60 degrees C. The estimated latency of release seems more related to the heating pattern (i.e. to laser parameters) than to the liposomes.

CONCLUSION

This preliminary study assesses the possible use of laser-induced release of liposome-encapsulated dye to monitor tissue temperature and then thermal damage.