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目的：制备并表征柠檬酸（citric acid，CA）修饰的超顺磁性氧化铁纳米粒（superparamagnetic iron oxide nanoparticles，SPIONs）用于磁靶向、热疗和磁共振成像（magnetic resonance imaging，MRI）。方法：通过共沉淀法制备柠檬酸修饰的 SPIONs（CA-SPIONs），并通过磁铁、透射电子显微镜、激光粒度测定仪、傅里叶转换红外（fourier transform infrared，FT-IR）光谱仪、热重-差热同步分析仪、振动样品磁强计、X 射线衍射仪分别对 CA-SPIONs 的磁响应性、形态、粒径、红外特征、柠檬酸的质量分数、磁学性质、X 射线衍射图谱等进行表征；通过高频感应加热机对 CA-SPIONs 的发热性能进行考察；通过 3.0 T 的 MRI 扫描仪对 CA-SPIONs 的横向弛豫效能（r2）进行评价。结果：制备的CA-SPIONs 在水中分散性良好，呈深黑色，具有良好的磁响应性，其形态圆整、大小均一，平均粒径在 12 nm 左右，水力学平均粒径为（72.35 ± 4.47） nm，多分散系数为 0.231 ± 0.029。红外光谱结果证明 CA-SPIONs 表面成功修饰上了柠檬酸，修饰的柠檬酸所占的重量百分比为 9.0%。CA-SPIONs 具有良好的超顺磁性，其饱和磁化强度为 63.58 emu/g；CA-SPIONs为反尖晶石型结构，经Debye-Scherrer 半宽公式可计算出晶粒大小为 12.4 nm；在 9 A和 45~50 k Hz 的交变电磁场下，CA-SPIONs 呈现出良好的发热性能，比吸收率（specific absorption rate，SAR）值为 26 W/g；在 3.0 T 的 MRI 扫描仪下，测得 CA-SPIONs 的 r2为 338 (mmol/L)-1·s-1，表明 CA-SPIONs 具有良好的 MRI 负性对比增强作用。结论：柠檬酸修饰的 SPIONs 有希望用于磁靶向、热疗和 MRI 诊断。
Objective: To prepare and characterize superparamagnetic iron oxide nanoparticles (SPIONs) modified by citric acid (CA) for magnetic targeting, hyperthermia and magnetic resonance imaging (MRI). METHODS: Citric acid-modified SPIONs (CA-SPIONs) were prepared by co-precipitation method and characterized by means of magnet, transmission electron microscopy, laser particle sizer, Fourier transform infrared spectroscopy, Differential thermal synchronous analyzer, vibrating sample magnetometer and X-ray diffractometer were used to measure the magnetic response, morphology, particle size, infrared characteristics, mass fraction of citric acid, magnetic properties and X-ray diffraction of CA-SPIONs The thermal performance of CA-SPIONs was investigated by high-frequency induction heating machine. The lateral relaxation efficiency (r2) of CA-SPIONs was evaluated by 3.0 T MRI scanner. Results: The prepared CA-SPIONs was well dispersed in water with a dark black color and good magnetic responsiveness. The average diameter of the CA-SPIONs was about 12 nm and the mean size of hydraulics was (72.35 ± 4.47 ) Nm, polydispersity coefficient is 0.231 ± 0.029. The result of FTIR showed that the surface of CA-SPIONs was successfully modified with citric acid, and the percentage of modified citric acid was 9.0%. CA-SPIONs have good superparamagnetism with a saturation magnetization of 63.58 emu / g; CA-SPIONs are anti-spinel structures with a calculated Debye-Scherrer half-width formula of 12.4 nm; A and 45 ~ 50 k Hz alternating electromagnetic field, CA-SPIONs showed good heating performance, the specific absorption rate (SAR) value of 26 W / g; 3.0 T MRI scanner, measuring The r2 of CA-SPIONs was 338 (mmol / L) -1 · s-1, which indicated that CA-SPIONs had a good MRI negative contrast enhancement effect. Conclusion: Citrate-modified SPIONs are promising for magnetic targeting, hyperthermia and MRI diagnosis.