Studies On Magnetic Nanocomposite Particles As Drug Carriers For Photodynamic Therapy Agents

Photodynamic therapy (PDT) is a recently developed therapeutic modality for cancer diagnosis and treatment of various types of tumors by irradiating a photosensitizer with light to produce reactive oxygen species in targeted cells. PDT has made great progress in clinical applications, however, it still faces many difficulties such as lower water-solubilty of the photo sensitizers which might reduce their bioavailability and poor selectivity of photosensitizers against tumor cells which might cause side effects. Magnetic nanoparticle has been widely used in drug delivery system in recent years. After surface modifications, the magnetic nanoparticles loaded the photosensitizer may get access to tumor cells more easily in magnetic field, therefore enhancing the bioavailabity of the photosensitizer and reducing its side effects.When consulting large amounts of literature, we synthesised three types of nanocomposite particles, and studied their interactions with DNA when they were used as drug delivery system for PDT drugs. Our work are summarized as follows.1. Superparamagnetic nanoparticles of Fe3O4 were prepared by coprecipitation according to reported procedures, and then were modified with citric acid, tartaric acid and vitamin C respectively. After that, three types of silica magnetic nanocomposite particles, (Fe3O4/CA)@SiO2, (Fe3O4/TA)@SiO2 and (Fe3O4/Vc)@SiO2 were obtained by sol-gel method using TEOS as silicon source. These nanoparticles which were characterized by XRD and IR, had average diameters of about 12 nm.2. When photosensitizers such as Pt(4-CH3-OPDA)(OPDA), Pt(4-NO2-OPDA)(OPDA) and Pt(DABA-Na)(OPDA) were absorbed sufficiently on silica magnetic nanocomposite particles respectively, we obtained nine different types of photosensitizer-loaded silica magnetic nanocomposite particles. These composite nanoparticles were characterized by XRD, IR and UV-Vis spectra, and their drug-loading capability were also determined by UV-Vis spectra.3. Interactions of photosensitizer-loaded silica magnetic nanocomposite particles with plasmid pBR322DNA were investigated by agarose gel electrophoresis. The results showed that photosensitizer-loaded silica magnetic nanocomposite particles could result in apparent damage of DNA under red light. Therefore, these photosensitizer-loaded silica magnetic nanocomposite particles might have potential applications in PDT therapy.