Synthesis of Magnetite-Silica Core Shell Nanostructures for Photodynamic Therapy

Abstract

Photodynamic Therapy (PDT) is a new and minimally invasive cancer treatment modality based on the photo-activation of a light-sensitive drug, photosensitiser (PS). This drug in turn generates singlet oxygen (when activated) in the malignant tissue and induces tissue necrosis or apoptosis This leads to a number of biological effects including damages to proteins, nucleic acids, lipids, and other cellular components, and often resulting in cell death and possible activation of the immune system to attack the tumour. This mode of therapy is a promising modality of treatment to malignant cancer tumours. Core-shell nanostructures have emerged as an important class of functional materials with potential applications in diverse fields, especially in health sciences. Magnetic nanostructures have potential applications in many biological and medical fields such as drug delivery, hyperthermia treatment, magnetic resonance contrast enhancement and cell separation. In the present work, we report here synthesis and properties of a unique drug delivery system, which could be used for diagnostic and therapy purposes. Magnetite nanoparticles were synthesized by traditional coprecipitation route. These single domain magnetic nanoparticles were loaded into the surface modifiable shell of silica. Photosensitizer drug methylene blue was co-loaded into the silica shell by demethylation reaction. Hydrolysis and condensation kinetics have been established to control the shell size. Fabricated drug delivery system was characterized by XRD, FTIR, TEM, SEM, UV-visible spectroscopy and VSM measurements. X-ray study confirms the formation of single phase magnetite nanoparticles with average size of 13.2 nm. Formation of silica shell was confirmed from the FTIR spectroscopy. Physical size of the magnetite core is 14.4 nm, which was determined through TEM measurements. This is in good agreement with the X-ray analysis. TEM micrograph also reveals that the magnetite nanoparticles are polydispersity in nature. The loading of methylene blue was also confirmed from UV-visible spectra. Room temperature magnetization measurement confirms the superparamagnetic nature of nanoparticles. The saturation magnetization of nanostructures decreases as the amount of silica in the sample increases. This is due to the increasing diamagnetic contribution from the silica shell. The designed drug delivery system can be simultaneously loaded with multiple photosensitizer drugs and may provide a platform for controlled and sustained delivery of toxins to cancer tumors with minimal size effects.