title: A photodependent switch of liposome stability and permeability.
abstract: Liposomes offer a method to encapsulate high concentrations of a drug, protecting the therapeutic upon in vivo administration. With an appropriate mechanism to manipulate lipid bilayer permeability, liposomes have the potential to deliver encapsulated drugs in a spatially and temporally controlled manner. In this investigation, the photosensitizer aluminum phthalocyanine disulfonic acid (AlPcS(2)) is identified as a modulator of the colloidal properties of liposomes. AlPcS(2) adsorption to liposomes stabilizes lipid bilayers and reduces permeability. Spectroscopic data suggests that AlPcS(2) interacts with the phospholipid to increase lipid bilayer stability. In the presence of AlPcS(2), the liposome permeability was five times lower than that without the photosensitizer. This results in more stable liposome systems that contain higher doses of the encapsulated material for longer. Then, upon irradiation of the AlPcS(2)-liposome system with tissue penetrating red light, lipid bilayer permeability increases 10-fold over the baseline. The release is shown to be a singlet oxygen mediated process, due to the type II photodynamic action of AlPcS(2). It is concluded that this activity provides a novel photorelease mechanism for liposome mediated drug delivery.
authors.affiliation: Department of Biochemistry, Laboratory for Intelligence Modeling & Neurophysics, Boston University School of Medicine, 650 Albany St., X-140, Boston, Massachusetts 02118, United States. erandles@bu.edu
authors.forename: Edward G
authors.initials: EG
authors.lastname: Randles
authors.forename: Peter R
authors.initials: PR
authors.lastname: Bergethon
mesh_terms: D008051:Lipid Bilayers / Q000737:chemistry; D008081:Liposomes / Q000737:chemistry*; D008958:Models, Molecular; D010539:Permeability; D055668:Photochemical Processes
chemical_list: D008051:Lipid Bilayers; D008081:Liposomes