【摘要】 具有超顺磁特性的Fe3O4纳米磁性粒子在外场中被极化时会产生沿极化方向的宏观磁矩,当撤销极化磁场后,利用高灵敏的高温超导量子干涉仪(SQUID)测量磁性粒子的磁弛豫行为.由于小尺度的磁性粒子磁性衰减很快,其行为遵循布朗弛豫;相较而言,通过生物待标记物连接的较大尺度磁性粒子或发生偶连的磁性团簇磁性衰减较慢,满足尼尔弛豫的条件.根据磁性颗粒的磁弛豫特性配合超导SQUID的低噪声实现对磁性粒子标记的微量生物待标记物的免疫检测.分别对平均尺寸为144nm的聚苯乙烯磁珠和406nm的二氧化硅磁珠的磁性衰减信号进行测量,得到了一些初步的实验结果.前者聚苯乙烯磁珠样品因磁珠尺寸太小,磁弛豫太快,未见明显的响应曲线;而后者的弛豫曲线遵循尼尔弛豫指数关系.结果表明粒子的有效弛豫依赖于磁性团簇的尺度.并且通过加大极化场,可以增强磁珠的尼尔弛豫信号,提高测量灵敏度。更多还原

【Abstract】 Magnetization of superparamagnetic Fe3O4 magnetic nanoparticles(MNPs)induces with the external magnetic field,MNPs relax when the field is turned off and relax signal can be detected by the sensitive high temperature superconducting quantum interference device(SQUID).Small MNPs relax rapidly by Brownian rotation;relatively,MNPs that are bound to the big bio-target recover slowly and undergo Néel relaxation.The immunoassay of MNPs bound bio-target with Néel relaxation is realized basing on SQUID with excellent noise level.We get primary results through detecting 144nm diameter polystyrene beads and 406nm diameter silica beads as a contrast sample.The former sample rotates too quickly to be detected because of its small size;the latter follows Néel curve.The measurement shows that effective relaxation signal depends on the size of bound clusters.Bigger magnetic field may enhance Néel signal and improve sensitivity.更多还原