Preparation, Characterization, and Spectral Property Studies on Methotrexate Conjugated Multifunctional Fe₃O₄-Pyropheophorbide-a Fluorescence Nanoparticles

Novel antitumor drug methotrexate (MTX) and fluorescence photosensitizer pyropheophorbide-a (PPa) conjugated multifunctional magnetic fluorescence nanoparticles Fe₃O₄@SiO₂–NH₂@MTX@PPa (MFMTXPPa) were designed and prepared for chemotherapy, photodynamic therapy (PDT) and medical fluorescence imaging. Fe₃O₄@SiO₂–NH₂ nanoparticles were firstly synthesized by a sol–gel process. Then methotrexate and pyropheophorbide-a were successively anchored on the surface of core–shell Fe₃O₄@SiO₂–NH₂ nanoparticles via covalently imide bond. The phase structure, composition, morphology, zeta potential, magnetic properties of nanoparticles were characterized by X-ray powder diffraction, Fourier transform infrared spectrometer, transmission electron microscopy, zeta potential, vibration sample magnetometer, thermogravimetric analysis, respectively. Meanwhile, we studied the effect of pH and different polar solvents on the absorption and fluorescence spectrum of MFMTXPPa. Our results indicated that MFMTXPPa preferentially aggregated in the acidic conditions but maintained monomeric form in alkaline conditions. Aggregations exhibit markedly influence on the absorbance and fluorescence intensity. In addition, we found that MFMTXPPa has high magnetization (46.7 emu/g), good water-solubility and dispersity in polar solvents, strong fluorescence intensity in near neutral conditions, and excellent stability in the acid-base system, which may be a potential candidate in the field of chemotherapy, PDT and fluorescence imaging.