title: Photochemical and photodynamic properties of vitamin B2--riboflavin and liposomes.
abstract: Ocular neovascular disease represents an important cause of blindness today. In this paper, it was used a model to evaluate the vaso-occlusive potential of photodynamic therapy with B2 vitamin. Neovascularization induced în an occular cornea consists of an easily accessible monolayer-like neovascular net within a transparent matrix. This fact allows studying the efficiency of occlusion în an isolated neovascular structure. This study is a requirement for the transport evaluation and photodynamic efficiency of this drug. Both riboflavin and the DPBF are embedded în the phospholipid bilayer. The quantum yield of DPBF photooxidation and riboflavin singlet oxygen generation are higher by comparison with water (13-35 s în liposomes and 0.4 s în water), due to the higher lifetime of singlet oxygen în liposomes and due to the special transport mechanism of B2 inside of liposomes. The photochemical behavior of riboflavin (Vitamin B2) aqueous solution and în unilamellar liposomes of dipalmitoyl phosphatidylcholine (DPPC) during the sensitized photooxidation of 1,3-diphenylisobenzofuran (DPBF) are discussed în this paper. Some structural aspects of DPPC liposomes, have been studied, too. The first step în the sequence of vesicle shape transformations, the spherical to polygonal shape transition, occurs în a very narrow temperature range, i.e., during the gel-to-liquid crystalline phase transition. At different temperatures (30,37-42 degrees C) could be seen the sequence for the vesicle form: spherical-polygonal-ellipsoidal, attributable to the lipid domain coexistence on the macroscopic structure of liposomes. The incorporation of B2 Vitamin eliminates the ellipsoidal form of DPPC, even at high temperature, because B2 has a very small molecule able to be encapsulated into DPPC vesicle. Also, the incorporation of B2 increase the DPPC diameter, all these observations being obtained by optical confocal microscopy.
authors.affiliation: Institute for Chemical Research-Icechim, Chemical Analysis Department, Splaiul Independentei 202, Bucharest-79611, Romania.
authors.forename: M A
authors.initials: MA
authors.lastname: Ioniţă
authors.forename: R M
authors.initials: RM
authors.lastname: Ion
authors.forename: B
authors.initials: B
authors.lastname: Cârstocea
mesh_terms: D006801:Humans; D008081:Liposomes; D008268:Macular Degeneration / Q000188:drug therapy; D017319:Photosensitizing Agents / Q000008:administration & dosage / Q000737:chemistry*; D012256:Riboflavin / Q000008:administration & dosage / Q000737:chemistry*; D013050:Spectrometry, Fluorescence
chemical_list: D008081:Liposomes; D017319:Photosensitizing Agents; D012256:Riboflavin