الفهرس 
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Abstract
Photosensitive liposomes are the most flexible approach that addresses the problem of slow passive drug release from liposomal vesicles. The present study investigates the photoinduced drug release from different photosensitive liposomal preparations as well as the liposomal membrane behavior of each preparation as a function of different factors. Photosensitive liposomes composed of dipalmitoyl phosphatidylcholine (DPPC) were prepared with various amounts of dioleoyl phosphatidylcholine (DOPC). Zinc (II) phthalocyanine (ZnPc) was used as the membrane sensitizer while rose bengal (RB) as the model drug. The encapsulation efficiencies (EE) of ZnPc and RB as well as the dark and the photo-induced RB release rates were calculated for each formulation. Differential Scanning Calorimetry (DSC) was also performed to study the liposomal membrane behavior after incorporation of DOPC, ZnPc and RB as well as after laser irradiation. The EE of both ZnPc and RB decreased significantly at high DOPC concentrations (50% and 75% w/w). Laser irradiation did not affect significantly the release of RB from DPPC liposomes while significantly increasing its release from all DOPC containing liposomes. DSC measurements showed that under dark conditions DOPC incorporation into the liposomal membrane disrupted the tight packing of DPPC tilted chains causing the disappearance of DPPC pre-transition while ZnPc incorporation increased the membrane packing as evidenced by the increase in the main transition temperature of all formulations. On the other hand, incorporating RB caused membrane destabilization. Upon irradiation membrane disruption occurred only in case of DOPC containing liposomes due to the peroxidation of double bonds of DOPC chains.