Investigation of factors affecting controlled release from photosensitive DMPC and DSPC liposomes.

Aysegul Aygun, Kathryn Torrey, Ashok Kumar, Larry D Stephenson

Index: Appl. Biochem. Biotechnol. 167(4) , 743-57, (2012)

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Abstract

An investigation of liposomes comprised of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) or 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC) lipids with cholesterol and zinc phthalocyanine (ZnPC) revealed that several fundamental liposome properties are influenced by composition and by lipid-specific features. DMPC and DSPC liposomes were synthesized, and their compositional changes, encapsulation capacities, morphologies, and release properties were evaluated. In this research, liposome degradation, lysis, and content release were initiated by photolysis, i.e., rupture induced by exposure to light. A controlled release mechanism was created through the introduction of photosensitizers (i.e., ZnPC) embedded within the cholesterol-stabilized liposome membrane. The light wavelength and light exposure time accelerated photodegradation properties of DMPC liposomes compared to DSPC liposomes, which exhibited a slower release rate. Morphological changes in the liposomes were strongly influenced by light wavelength and light exposure time. For both the DMPC and DSPC liposomes, visible light with wavelengths in the red end of the spectrum and broad spectrum ambient lighting (400-700 nm) were more effective for lysis than UV-A light (365 nm). Heating liposomes to 100 °C decreased the stability of liposomes compared to liposomes kept at room temperatures. In addition, the optimal lipid-to-cholesterol-to-photoactivator ratio that produced the most stable liposomes was determined.