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.

Encapsulation of methylene blue in polyacrylamide nanoparticle platforms protects its photodynamic effectiveness

“…In recent years, with the advancement of nanotechnology, engineered nanoparticles have received attention as a possible means of encapsulating and delivering PDT agents. Research in our laboratories [17][18][19][20][21][22] and elsewhere [23,24] has demonstrated the utility of nano-structured materials, which employ biocompatible nanoparticle matrices encapsulated with efficient photo-active molecules, for PDT. Our concept of a nanoparticle platform (NP) was initiated by the design of Photonic Explorers for Biomedical use by Biologically Localized Embedding, termed PEBBLEs.…”

Synthesis and Characterization of Star-Shaped Porphyrin-cored Poly(Glutamic Acid) Conjugates as Highly Efficient Photosensitizers

“…The intensities of absorption at 456 nm were plotted against irradiation time. The singlet oxygen quantum yield (η) of SPPLGA in DMF was calculated using following equation [23]:…”

“…DPBF is a singlet oxygen quencher which can qualitatively establish the production of singlet oxygen, which result in a decreased intensity of the DPBF fluorescence band at 414 nm. According to the reported singlet oxygen generation estimation method, The singlet oxygen quantum yield (η) of polymer were evaluated by comparison with those obtained in previous work for 5,10,15,20-tetraphenylporphyrin (TPP) (0.67±0.09) [23]. In Fig.…”

Recent advances in the development of magnetically recoverable metal nanoparticle catalysts

“…The samples were analyzed by transmission electron microscopy (TEM), which revealed particles in the range of 30-40 nm, with predominance of aggregates in a pearl necklace-like-structure. The material, so obtained, was used in applications that included immobilizing of drugs for biomedical applications, 49 as well as catalysts for magnetic separation. 50 Because it requires high dilution of the coating solution, this method limits the amount of material obtained to hundreds of milligrams in each reaction.…”