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Methylene blue-containing silica-coated magnetic particles: a potential magnetic carrier for photodynamic therapy
Dayane B Tada1, Lucas L R Vono, Evandro L Duarte
1Institute of Chemistry, University of São Paulo, São Paulo 05508-000, São Paulo, Brazil.
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.
Insights
We developed silica-coated magnetic nanoparticles loaded with methylene blue for photodynamic therapy. These particles can generate singlet oxygen, offering potential for combined therapeutic and diagnostic applications.
Area of Science:
- Materials Science
- Nanotechnology
- Biomedical Engineering
Background:
- Methylene blue (MB) is a photosensitizer with potential in photodynamic therapy.
- Developing targeted drug delivery systems is crucial for enhancing therapeutic efficacy.
- Magnetic nanoparticles offer possibilities for MRI contrast enhancement and targeted delivery.
Purpose of the Study:
- To prepare and characterize methylene blue-loaded silica-coated magnetic nanoparticles.
- To evaluate the singlet oxygen generation and release properties of the encapsulated MB.
- To assess the magnetic properties and potential for combined therapy and diagnostics.
Main Methods:
- Synthesis of silica-coated magnetic nanoparticles with entrapped methylene blue.
- Characterization using transmission electron microscopy (TEM), light scattering, and X-ray diffraction.
- Detection of singlet oxygen using phosphorescence and chemical trapping methods.
- Magnetization measurements to confirm superparamagnetic behavior.
Main Results:
- Successfully synthesized ~30 nm silica spheres containing 11 nm magnetic nanoparticles and entrapped MB.
- Confirmed singlet oxygen generation by immobilized MB, with determined lifetimes in acetonitrile and water.
- Observed a reduced singlet oxygen quantum yield (6%) upon encapsulation.
- Demonstrated superparamagnetic behavior with reduced saturation magnetization.
Conclusions:
- The developed silica-coated magnetic nanoparticles effectively encapsulate methylene blue.
- The platform shows potential for photodynamic therapy due to singlet oxygen generation.
- The magnetic properties suggest utility as MRI contrast agents.
- This particle platform offers combined therapeutic and diagnostic capabilities with drug targeting potential.
