title: Methylene blue-containing silica-coated magnetic particles: a potential magnetic carrier for photodynamic therapy.
abstract: We present the preparation and characterization of methylene blue-containing silica-coated magnetic particles. The entrapment of methylene blue (MB), a photodynamic therapy drug under study in our group, in the silica matrix took place during the growth of a silica layer over a magnetic core composed of magnetite nanoparticles. The resulting material was characterized by transmission electron microscopy (TEM), light scattering, and X-ray diffraction. It is composed of approximately 30 nm silica spheres containing magnetic particles of 11 +/- 2 nm and methylene blue entrapped in the silica matrix. The immobilized drug can generate singlet oxygen, which was detected by its characteristic phosphorescence decay curve in the near-infrared and by a chemical method using 1,3-diphenylisobenzofuran to trap singlet oxygen. The lifetime of singlet oxygen was determined to be 52 micros (in acetonitrile) and 3 micros (in water), with both values being in good agreement with those in the literature. The release of singlet oxygen (etaDelta) was affected by the encapsulation of MB in the silica matrix, which caused a reduction to 6% of the quantum yield of MB free in solution. The magnetization curve confirmed the superparamagnetic behavior with a reduced saturation magnetization in respect to uncoated magnetic nanoparticles, which is consistent with the presence of a diamagnetic component over the magnetite surface. The result is a single particle platform that combines therapy (photosensitizer) and diagnostic (MRI contrast agent) possibilities at the same time, as well as drug targeting.
authors.affiliation: Institute of Chemistry, University of São Paulo, São Paulo 05508-000, São Paulo, Brazil.
authors.forename: Dayane B
authors.initials: DB
authors.lastname: Tada
authors.forename: Lucas L R
authors.initials: LL
authors.lastname: Vono
authors.forename: Evandro L
authors.initials: EL
authors.lastname: Duarte
authors.forename: Rosangela
authors.initials: R
authors.lastname: Itri
authors.forename: Pedro K
authors.initials: PK
authors.lastname: Kiyohara
authors.forename: Maurício S
authors.initials: MS
authors.lastname: Baptista
authors.forename: Liane M
authors.initials: LM
authors.lastname: Rossi
mesh_terms: D003287:Contrast Media / Q000737:chemistry*; D052203:Ferrosoferric Oxide / Q000737:chemistry*; D008279:Magnetic Resonance Imaging; D008280:Magnetics; D008751:Methylene Blue / Q000737:chemistry* / Q000627:therapeutic use; D046529:Microscopy, Electron, Transmission; D053758:Nanoparticles / Q000737:chemistry* / Q000627:therapeutic use / Q000648:ultrastructure; D010778:Photochemotherapy; D017319:Photosensitizing Agents / Q000737:chemistry* / Q000627:therapeutic use; D012822:Silicon Dioxide / Q000737:chemistry* / Q000627:therapeutic use; D026082:Singlet Oxygen / Q000737:chemistry
chemical_list: D003287:Contrast Media; D017319:Photosensitizing Agents; D026082:Singlet Oxygen; D012822:Silicon Dioxide; D008751:Methylene Blue; D052203:Ferrosoferric Oxide