Study of magnetic ferrite nanoparticles labeled with 99mTc-pertechnetate

This study examined the applications of novel non-polymer magnetic ferrite nanoparticles (Fe₃O₄ NPs) labeled with ^99mTc-pertechnetate (^99mTcO₄ ⁻). The radiochemistry, chemistry, and biodistribution of Fe₃O₄ NPs labeled with ^9mTcO₄ ⁻ were analyzed. This paper employed instant thin layer chromatography and magnetic adsorption to evaluate the labeling efficiency and stability of ^99mTc-Fe₃O₄ at various reaction conditions. A scanning electron microscope, X-ray diffractometer, Fourier transform infrared spectrometer, laser particle size analyzer, and superconducting quantum interference device magnetometer were used to analyze the physical and chemical properties of the Fe₃O₄ and ⁹⁹Tc-Fe₃O₄ nanoparticles. The biodistribution and excretion of ^99mTc-Fe₃O₄ were also investigated. Radiochemical analyses showed that the labeling efficiency was over 92% after 1 min in the presence of a reducing agent. Hydroxyl and amine groups covered the surface of the Fe₃O₄ particles. Therefore, ⁹⁹Tc (VII) reduced to lower oxidation states and might bind to Fe₃O₄ NPs. The sizes of the ⁹⁹Tc-Fe₃O₄ NPs were about 600 nm without ultrasound vibrations, and the particle sizes were reduced to 250 nm under ultrasound vibration conditions. Nonetheless, Fe₃O₄ NPs and ⁹⁹Tc-Fe₃O₄ NPs exhibited superparamagnetic properties, and the saturation magnetization values were about 55 and 47 emu/g, respectively. The biodistribution showed that a portion of the ^99mTc-Fe₃O₄ nanoparticles might embolize in a pulmonary capillary initially; the embolism radioactivity was cleared from the lungs and was then taken up by the liver. ^99mTc-Fe₃O₄ metabolized very slowly only 1–2% of the injected dose (ID) was excreted in urine and about 2.37% ID/g was retained in the liver 4 h after injection. Radiopharmaceutically, ^99mTc-Fe₃O₄ NPs displayed long-term retention, and only ^99mTc-Fe₃O₄ NPs that dissociated to free pertechnetate could be excreted in urine. This research evaluated the feasibility of non-polymer magnetic ferrite NPs labeled with technetium as potential radiopharmaceuticals in nuclear medicine.