Improvement of water-dispersibility of composite nanoparticles composed of magnetic iron oxide coated with noble metal and dot formation by magnetic field.

我们进行了由金和磁性氧化铁组成的复合纳米粒子的改进研究，其中前者是单纳米颗粒，后者是更大的颗粒。为了合成这些粒子，将含有金离子、预先形成的氧化铁纳米粒子、足够数量的酒精和聚合物的水溶液用^<60>Co γ射线、高能电子或超声波照射。水中的金离子被辐照原位形成的自由基还原成金属颗粒，颗粒在水中同时迁移后成为稳定的氧化铁颗粒。这是一种在室温下的水溶液中进行的非常简单的方法。我们做了很多实验，找到了很好的分散性条件，可以在水中保持一种分散性数周。这种分散性是由湿式磨珠机得到的。我们还研究了它们的性质，并通过利用金对含硫分子的高亲和力和氧化铁的磁性，对它们进行修饰，以用于快速和选择性地分离生物分子，如DNA、蛋白质或抗原。已经证明，这种粒子能够磁性分离核苷酸，其灵敏度高于市售粒子。我们还尝试了将这些粒子带电到亚毫米宽的通道中的实验。将颗粒分散溶液与另一种溶液混合，用小型永磁体芯片施加磁场。我们成功地证实了磁粒子被磁场吸引形成一个点。

We executed studies for improvement of composite nanoparticles consisting of gold and magnetic iron oxide, in which the former is of single-nano-sized grains and the latter is of larger particles. To synthesize the particles, an aqueous solution containing gold ions, preformed iron oxide nanoparticles, adequate amounts of alcohol and polymer is irradiated with ^<60>Co γ-rays, high energy electrons or ultrasonics. Aqueous gold ions are reduced to form metallic grains by radicals in-situ formed by the irradiation, and the grains are stabilized iron oxide particles after meanwhile migration in water. It is a very simple method proceeding in an aqueous solution at room temperature under ambient atmosphere. We tried many experiments and found conditions providing a good dispersiblity, that they kept a dispersion in water for weeks. This dispersibility was given by a wet beads mill. We as well studied their properties and modifying them for application to a quick and selective separation of biomolecules such as DNA, proteins or antigens, by exploiting Au's high affinity to sulfur-containing molecules and magnetism of the iron oxide. It was already demonstrated that the particles are able to magnetically separate nucleotides with sensitivity higher than those of commercially available particles. We also tried experiments that these particles are charged into a channel with sub-millimeter width. The particle dispersing solution was mixed with an another solution and applied with a magnetic field with a small permanent magnet chip. We successfully confirmed the magnetic particles were attracted by the field to form a dot.