磁性铁氧化物纳米材料在肿瘤成像中的应用

Application of magnetic iron oxide nanomaterials in tumor imaging

恶性肿瘤已经成为影响全人类健康的一大疾病,但因为其隐匿性强,且缺乏高效准确的诊断方法,使得早期诊疗目前仍较为困难.磁性铁氧化物纳米材料由于其出色的生物相容性、超顺磁性和尺寸效应等特性在磁共振成像新型造影剂的研发和多模态成像中发挥着重要作用.基于磁性铁氧化物纳米材料开发的新型磁共振成像(MRI)T_(1)造影剂与T_(1)-T_(2)协同造影剂不仅有较高的成像分辨率,且有较好的生物相容性.作为一种优良的多功能纳米平台,磁性铁氧化物纳米材料通过与不同显像模块的连接可以实现MR-光学显像、MR-核素显像以及多种新兴的多模态显像技术,还可以通过与主动靶向分子的连接实现对肿瘤组织的特异性靶向,因此在肿瘤诊疗中具有良好的应用前景.本文结合近年来磁性铁氧化物纳米材料在成像方面的研究工作,深入探讨和分析了磁性铁氧化物纳米材料在肿瘤诊疗中的应用进展.

The incidence of malignant tumor increases year by year,becoming one of the major diseases affecting the health globally.Early diagnosis is the key to reduce the burden of cancer morbidity and mortality.However,due to inconspicuous characteristics in the early stage of cancer development,and the lack of efficient and accurate diagnostic methods,the early cancer diagnosis is far from satisfied.Iron oxide nanomaterials have shown great potential in cancer diagnosis because of their unique size-dependent properties,surface functionalization feasibility and good biocompatibility.As the only inorganic nanomaterials approved by FDA for clinical use,great progress has been achieved recently for iron oxide nanomaterials in materials design and biomedical applications,especially,being used as novel contrast agents for magnetic resonance imaging(MRI).This review will discuss the application of magnetic iron oxide nanomaterials in cancer diagnosis in recent years.At first,magnetic iron oxide nanomaterials are ideal MRI contrast agents,for the imaging modal(T_(1),T_(2) or T_(1)-T_(2))can be adjusted by the magnetic iron oxide nanomaterials diameters and morphologies.Superparamagnetic iron oxide nanoparticles(diameter>5 nm)are typical MRI T_(2) contrast agents,while exceedingly small magnetic iron oxide nanoparticles(ES-MIONs,<5 nm)are an efficient and reliable T_(1) contrast agent.Even T_(1)-T_(2) dual-modal contrast agents can be obtained by separating T_(1) contrast agent(paramagnetic shell)and T_(2) contrast agent(superparamagnetic nanoparticle core)with a non-magnetic silica layer,called artifact filtering nanoparticle imaging agent,AFIA.This dual-mode nanoparticle imaging agent(AFIA)can perform the"AND"logic gate algorithm in the post data processing,displaying areas that only show high MRI contrast differences in both T_(1) and T_(2) images,thereby eliminating the pseudo-errors(artifacts)in the original image.That strategy can help clinicians diagnose and evaluate diseases such as early tumors,vascular systems disease and central nervous system disease that are greatly disturbed by artifacts with more efficiency.Secondly,different imaging technologies(MRI,PET,SPECT,X-ray,optical imaging,etc.)have their pros and cons in terms of spatial resolution,sensitivity,penetration ability,and so on and so forth.If multi-modal imaging can be achieved,it will be possible to diagnose tumor more accurately and sensitively.For example,the optical imaging probes are connected to the magnetic iron oxide nanomaterials to obtain MRI-optical dual-mode imaging agents for highly sensitive imaging of sub-millimeter cell clusters.The dual-modality imaging system combining MRI and PET/SPECT can provide highsensitivity,high-resolution tomographic images,and at the same time obtain biological anatomical structure and biological metabolism information as well.With the quick development in nanomedicine,magnetic nanoparticles-based diagnostics are believed to play vital roles in cancer early diagnosis in the future.Active targeting technology is also an important research field of tumor diagnosis.The combination of bio-active molecules with magnetic iron oxide nanomaterials can increase the active targeting function on the basis of passive target aggregation via EPR effect.It is believed that in the near future,there will be more efficient targeted imaging materials emerging to evaluate and diagnose the basic situation of malignant tumors from multiple layers,making early diagnosis and treatment of cancer possible.