RELEASE OF FLUORESCEIN FROM THERMOSENSITI VE LIPOSOMES FOR A QUANTIFICATION OF LASER-INDUCED PHOTOCOAGULATION - IN-VIVO EX-VIVO PRELIMINARY-STUDY

Purpose: The aim of this in-vivo/ex vivo study was to assess the possi ble use of temperature sensitive liposomes in an established model suc h as the liver as a new approach to monitor the temperature induced by a laser. Method: Temperature sensitive liposomes (DSPC: DiStearoylPho phatidyl-Choline: critical temperature: 55 degrees C) loaded with carb oxy-fluoresceine were prepared by the Bancham procedure. These liposom es (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 in frared thermographic camera (Aga). The fluorescence emission was then measured with a fluorescent imaging system (Hamamatsu). Results: The d ye was released in response to laser energy. The amount of the drug re lease increased linearly with increasing temperature in the range 42 t o 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 asseses the possible use of laser- induced release of liposome-encapsulated dye to monitor tissue tempera ture and then thermal damage.