Laser mediated release of dye from liposomes

Liposomes made from phospholipids and containing sulforhodamine dye (1-50 mM) have been irradiated with nanosecond and picosecond laser pulses. Individual liposomes were locally heated by laser absorption of dye dimers during a single laser pulse, and heating was sufficient to release the liposome contents. The extent of dye release produced by a single laser pulse was shown to be quantitatively dependent on several interdependent variables, including dye concentration, liposome size, laser excitation parameters and initial temperature of the dye-liposome system. Fluorescence lifetime data having three components have been obtained and analyzed in terms of three dye environments. Quantitative estimates support a photo-induced thermal mechanism for liposome lysis and release of its contents. These results may be useful for laser induced delivery of therapeutic agents or other applications of lasers in biological systems.