Rotating magnetic field-controlled fabrication of magnetic hydrogel with spatially disk-like microstructures

Composite biomaterials with controllable microstructures play an increasingly important role in tissue engineering and regenerative medicine. Here, we report a magnetic hydrogel composite with disk-like microstructure fabricated by assembly of iron oxide nanoparticles during the gelation process in the presence of rotating magnetic field. It should be mentioned that the iron oxide nanoparticles here were synthesized identically following techniques of Ferumoxytol that is the only inorganic nanodrug approved by FDA for clinical applications. The microstructure of nanoparticles inside the hydrogel was ordered three-dimensionally due to the twist of the aligned chains of magnetic nanoparticles which leads to the lowest state of systematic energy. The size of microstructure can be tuned from several micrometers to tens of micrometers by changing the assembly parameters. With the increase of microstructure size, the magnetothermal anisotropy was also augmented. This result confirmed that the assembly-induced anisotropy can occur even for the several micron aggregates of nanoparticles. The rotating magnetic field-assisted technique is cost-effective, simple and flexible for the fabrication of composite hydrogel with ordered microstructure. We believe it will be favorable for the quick, green and intelligent fabrication of some composite materials.摘要具有可控微结构的复合生物材料在组织工程和再生医学中发挥着越来越重要的作用. 本文报道了在旋转磁场作用下, 通过组装氧 化铁纳米颗粒制备具有盘状微结构的磁性水凝胶复合材料. 组装用的磁性纳米材料是按照合成Ferumoxytol的方法制备而得, 也是唯一的 被FDA批准应用于临床的铁氧化物纳米颗粒. 磁性纳米颗粒的微观结构在水凝胶内部排列为三维有序. 其形成机理是由于磁性纳米颗粒 的排列链受到旋转磁场作用扭曲从而形成了微观结构系统能量的最低态. 通过改变组装参数, 可以将微结构尺寸从几微米调整到几十微 米. 随着组装结构体的增大, 其磁各向异性也得到相应的增强. 这种情况也证明了即使是微米级的纳米粒子聚集体, 也可以通过旋转磁场 组装诱导产生各向异性. 旋转磁场辅助技术制备有序微纳米结构水凝胶具有成本低、操作简单、灵活等优点. 我们相信利用这种方法将 有利于构建一些快速、绿色和智能制造的复合材料.