Institute of Natural Sciences and Mathematics, Ural Federal University, Ekaterinburg 620002, Russia.
Institute of Electrophysics, Ural Division RAS, Ekaterinburg 620016, Russia.
Sensors (Basel). 2018 Jan 16;18(1):257. doi: 10.3390/s18010257.
Magnetic biosensors are an important part of biomedical applications of magnetic materials. As the living tissue is basically a "soft matter." this study addresses the development of ferrogels (FG) with micron sized magnetic particles of magnetite and strontium hexaferrite mimicking the living tissue. The basic composition of the FG comprised the polymeric network of polyacrylamide, synthesized by free radical polymerization of monomeric acrylamide (AAm) in water solution at three levels of concentration (1.1 M, 0.85 M and 0.58 M) to provide the FG with varying elasticity. To improve FG biocompatibility and to prevent the precipitation of the particles, polysaccharide thickeners-guar gum or xanthan gum were used. The content of magnetic particles in FG varied up to 5.2 wt % depending on the FG composition. The mechanical properties of FG and their deformation in a uniform magnetic field were comparatively analyzed. FG filled with strontium hexaferrite particles have larger Young's modulus value than FG filled with magnetite particles, most likely due to the specific features of the adhesion of the network's polymeric subchains on the surface of the particles. FG networks with xanthan are stronger and have higher modulus than the FG with guar. FG based on magnetite, contract in a magnetic field 0.42 T, whereas some FG based on strontium hexaferrite swell. Weak FG with the lowest concentration of AAm shows a much stronger response to a field, as the concentration of AAm governs the Young's modulus of ferrogel. A small magnetic field magnetoimpedance sensor prototype with CoFeMoSiB rapidly quenched amorphous ribbon based element was designed aiming to develop a sensor working with a disposable stripe sensitive element. The proposed protocol allowed measurements of the concentration dependence of magnetic particles in gels using magnetoimpedance responses in the presence of magnetite and strontium hexaferrite ferrogels with xanthan. We have discussed the importance of magnetic history for the detection process and demonstrated the importance of remnant magnetization in the case of the gels with large magnetic particles.
磁性生物传感器是磁性材料在生物医学应用中的重要组成部分。由于生物组织基本上是一种“软物质”，本研究开发了具有微米级磁性颗粒的铁凝胶（FG），这些颗粒模拟了生物组织。FG 的基本组成包括聚丙烯酰胺的聚合物网络，通过单体丙烯酰胺（AAm）在水溶液中的自由基聚合在三个浓度水平（1.1 M、0.85 M 和 0.58 M）下合成，以提供具有不同弹性的 FG。为了提高 FG 的生物相容性并防止颗粒沉淀，使用了多糖增稠剂-瓜尔胶或黄原胶。FG 中磁性颗粒的含量根据 FG 的组成变化高达 5.2 wt%。比较分析了 FG 的机械性能及其在均匀磁场中的变形。填充有锶铁氧体颗粒的 FG 的杨氏模量值大于填充有磁铁矿颗粒的 FG，这很可能是由于聚合物亚链在颗粒表面的附着的特定特征所致。与瓜尔胶相比，基于黄原胶的 FG 更坚固且模数更高。基于磁铁矿的 FG 在磁场中收缩 0.42 T，而一些基于锶铁氧体的 FG 则膨胀。具有最低 AAm 浓度的弱 FG 对磁场的响应要强得多，因为 AAm 的浓度控制着铁凝胶的杨氏模量。设计了基于 CoFeMoSiB 快淬非晶 ribbon元件的小型磁阻抗传感器原型，旨在开发一种与一次性条形敏感元件配合使用的传感器。所提出的方案允许在存在含有黄原胶的磁铁矿和锶铁氧体铁凝胶的情况下，使用磁阻抗响应测量凝胶中磁性颗粒的浓度依赖性。我们讨论了磁历史对检测过程的重要性，并证明了在具有大磁性颗粒的凝胶的情况下，剩余磁化强度的重要性。
