Fast laser-induced solute release from liposomes sensitized with photochromic lipid: Effects of temperature, lipid host, and sensitizer concentration

Liposomes of gel-phase phospholipid have been prepared containing a photoch romic lipid sensitizer. A fast UV laser pulse isomerizes the sensitizer des tabilizing the lipid bilayer structure and causing release of trapped solut e. The kinetics of solute release have been investigated as a function of h ost lipid chain length, sensitizer concentration, and temperature, and the limits of liposome stability have been established. At low concentrations o f sensitizer, pulsed laser irradiation induces some solute release when con tinuous UV illumination is ineffective. Although rates of solute release us ually increase with temperature, at low sensitizer concentration in a rigid host, leakage at first increases but then decreases rapidly above a thresh old temperature. The results presented are relevant to the design of photos timulated drug delivery systems and to potential applications of photosensi tive liposomes as caging agents for biological effecters. (C) 1999 Academic Press.