Department of Applied Physics, University of Granada, Granada, Spain.
Soft Matter. 2017 Apr 19;13(16):2928-2941. doi: 10.1039/c7sm00388a.
We analyze the effect of nanoparticle concentration on the physical properties of magnetic hydrogels consisting of polymer networks of the human fibrin biopolymer with embedded magnetic particles, swollen by a water-based solution. We prepared these magnetic hydrogels by polymerization of mixtures consisting mainly of human plasma and magnetic nanoparticles with OH functionalization. Microscopic observations revealed that magnetic hydrogels presented some cluster-like knots that were connected by several fibrin threads. By contrast, nonmagnetic hydrogels presented a homogeneous net-like structure with only individual connections between pairs of fibers. The rheological analysis demonstrated that the rigidity modulus, as well as the viscoelastic moduli, increased quadratically with nanoparticle content following a square-like function. Furthermore, we found that time for gel point was shorter in the presence of magnetic nanoparticles. Thus, we can conclude that nanoparticles favor the cross-linking process, serving as nucleation sites for the attachment of the fibrin polymer. Attraction between the positive groups of the fibrinogen, from which the fibrin is polymerized, and the negative OH groups of the magnetic particle surface qualitatively justifies the positive role of the nanoparticles in the enhancement of the mechanical properties of the magnetic hydrogels. Indeed, we developed a theoretical model that semiquantitatively explains the experimental results by assuming the indirect attraction of the fibrinogen through the attached nanoparticles. Due to this attraction the monomers condense into nuclei of the dense phase and by the end of the polymerization process the nuclei (knots) of the dense phase cross-link the fibrin threads, which enhances their mechanical properties.
我们分析了纳米粒子浓度对由聚合物网络组成的磁性水凝胶的物理性质的影响，聚合物网络由嵌入磁性粒子的人类纤维蛋白生物聚合物和水基溶液组成。我们通过聚合主要由人类血浆和具有 OH 官能化的磁性纳米粒子组成的混合物来制备这些磁性水凝胶。显微镜观察表明，磁性水凝胶呈现出一些簇状的结，由几条纤维连接。相比之下，非磁性水凝胶呈现出均匀的网状结构，只有纤维对之间的单独连接。流变分析表明，刚性模量以及粘弹性模量随纳米粒子含量的增加呈二次方关系，遵循类似平方的函数。此外，我们发现存在磁性纳米粒子时凝胶点的时间更短。因此，我们可以得出结论，纳米粒子有利于交联过程，充当纤维蛋白聚合物附着的成核位点。纤维蛋白原的正基团与磁性粒子表面的负 OH 基团之间的吸引力定性地证明了纳米粒子在增强磁性水凝胶的机械性能方面的积极作用。事实上，我们开发了一个理论模型，通过假设通过附着的纳米粒子间接吸引纤维蛋白原，半定量地解释了实验结果。由于这种吸引力，单体凝结成密集相的核，并且在聚合过程结束时，密集相的核（结）交联纤维蛋白纤维，从而增强了它们的机械性能。
