A series of Fe_3-xGd_xO₄ (x = 0, 0.1, 0.2) nanoparticles with an average diameter of around 8 nm were prepared by the coprecipitation method and coated by citric acid (CA). The nanoparticles show superparamagnetic behavior at room temperature and transition to a blocked state, at a temperature from ~ 89 K to ~ 213 K, depending on Gd concentration. The saturation magnetization of Fe_3-xGd_xO₄ tended to drop for samples with a higher content of Gd. High colloidal stability is mandatory in medical applications of magnetic nanoparticles, and here we demonstrate a new procedure for its improvement. A colloidal sample of Fe₃O₄@CA was mechanically milled, after which dynamic light scattering and zeta potential measurements were used to monitor the hydrodynamic size and colloidal stability of the acquired suspensions. After 90 min of milling, the average hydrodynamic diameter decreased by 40%, and size distribution changed from polymodal to monomodal, while the negative zeta potential increased from − 30.5 mV to − 52.8 mV. Additionally, Fe_2.80Gd_0.20O₄@CA nanoparticles were embedded in human serum albumin to produce magnetic microspheres (MMS), which could be used as a drug delivery platform. FE-SEM images showed that magnetic nanoparticles form clusters within MMS.

 通过共沉淀法制备了一系列平均直径约为8 nm的Fe _3-x Gd _x O ₄（x = 0，0.1，0.2）纳米颗粒，并用柠檬酸（CA）包被。纳米粒子在室温下显示超顺磁性行为，并在约89 K至213 K的温度下转变为封闭状态，具体取决于Gd浓度。Fe _{3- x} Gd _x O ₄的饱和磁化强度对于具有较高Gd含量的样品而言趋于下降。高胶体稳定性在磁性纳米粒子的医学应用中是必不可少的，在这里我们展示了一种改进它的新方法。Fe ₃ O的胶体样品机械研磨₄ @ CA，然后使用动态光散射和ζ电势测量来监测获得的悬浮液的流体动力学尺寸和胶体稳定性。研磨90分钟后，平均流体动力学直径减小了40％，尺寸分布从多峰变为单峰，而zeta负电位从-30.5 mV增加到-52.8 mV。另外，将Fe _2.80 Gd _0.20 O ₄ @CA纳米颗粒嵌入人血清白蛋白中以产生磁性微球（MMS），该磁性微球可用作药物递送平台。FE-SEM图像显示磁性纳米颗粒在MMS中形成簇。