超顺磁性氧化铁纳米粒子在脑磁共振成像中的应用

超顺磁性氧化铁纳米粒子的磁性及生物相容性，使其在生物医学多个领域的应用研究都逐渐发展起来。本文介绍磁共振成像（MRI）及脑功能磁共振成像（fMRI）基本原理。列举不同性能的磁性氧化铁粒子作为磁共振成像对比剂在脑科学应用中的研究进展。表面结合单克隆抗体、蛋白质、多肽、核苷酸分子或其它特殊聚合物的磁性氧化铁粒子具有吸收特异性（靶向性），结合MRI可实现对脑部病变前期改变、药物输运及治疗的监测，对细胞、生物分子包括mRNA的成像及探测。经葡聚糖或聚乙二醇修饰的超顺磁性氧化铁纳米粒子血液半衰期较长，可作为对比剂用于脑fMRI成像。控制氧化铁纳米粒子的粒度及表面修饰物的物理化学性质、提高饱和磁化强度、借以接枝以各种靶向性的物质、开发具有荧光-磁性等多种性能的复合纳米粒子及掌握纳米粒子与生物分子、细胞、及生物组织之间的相互作用，则需要更深入的研究。

Application of superparamagnetic iron oxide nanoparticles as contrast agents in brain magnetic resonance imaging

Superparamagnetic iron oxide nanoparticles have a variety of biomedical applications because of their magnetic property and biocompatibility. The basic principles and parameters of the magnetic resonance imaging （MRI） and functional magnetic resonance imaging （fMRI） are presented. Recent advances of iron oxide nanoparticles with various properties acting as MRI contrast agents are described. The iron oxide nanoparticles modified or conjugated with monoclonal antibodies, proteins, peptides, nucleotides, and other particular polymers, are taken up specifically, and can be used as contrast agents in MRI to enhance detection of neurodegenerative diseases, to monitor targeted drug delivery and therapeutic processes, and to image targeted biomolecules or cells; Iron oxide nanoparticles coated with dextran or polyethylene glycol （PEG） have long blood half-life, and are used as fMRI contrast agents to measure haemodynamic changes after enhanced neural activity. Further studies are needed on the control of particle sizes and the physicochemical properties of the modifications, increase of crystallinity and consequently saturation magnetization, conjugation with different targeting substances, the development of hybrid nanoparticles with optical and magnetic properties, and comprehension of the interactions between the nanoparticles and biomolecules, cells and tissues.