近红外二区发光稀土纳米材料的设计及生物成像应用

Design of NIR-Ⅱ Emissive Rare-earth Nanoparticles and Their Applications for Bio-imaging

近年来,近红外二区(NIR-II,1000~1700 nm)荧光成像因其较高的空间分辨率、较深的组织穿透能力,在分子影像领域引起了广泛的关注。常见的NIR-II发光材料(如有机小分子、共轭聚合物、量子点等)通常具有光稳定性差、荧光量子产率低、斯托克斯位移小、荧光峰宽等问题,限制了这一新型成像技术的进一步发展与应用。稀土纳米材料由于其独特的发光特性,能够较好地克服这些不足,近年来不同结构的稀土纳米材料也逐渐被设计开发并应用于近红外二区荧光成像与检测,展示出了巨大的应用潜力。本综述首先介绍了稀土纳米材料的光学特性,然后按敏化离子的不同(Yb^(3+)、Nd^(3+)、Er^(3+)、Tm^(3+))详细介绍了近红外二区稀土纳米材料的设计方法及相关应用,最后对稀土纳米材料在近红外二区成像领域的进一步发展进行了展望。

In recent years, fluorescence imaging in the second near-infrared region (NIR-Ⅱ, 1000~1700 nm) has attracted lots of interests due to its unique advantages such as deep tissue penetration, low background and high spatial resolution. Commonly used NIR-Ⅱ probes such as small molecules, conjugated polymers and quantum dots, usually exhibit poor photostability, low quantum yield, small stokes shift and large half-peak width, which hinders the further development and application of NIR-Ⅱ imaging. Rare-earth based nanomaterials with unique optical properties have exhibited great potential for optical imaging. Rare-earth nanoparticles with metal ions as activators do not suffer from photobleaching and can provide narrow excitation/emission peaks with large stokes shift. Their emission is tuned with the choice of doped rare-earth ions and can maintain high quantum yield, which is different from other fluorophores. The fluorescence lifetime of rare-earth nanoparticles is also much longer than common fluorophores. All these features enable them as novel probes for in vivo fluorescence imaging and diagnosis in the NIR-Ⅱ region. This review briefly introduces the optical features of rare-earth nanoparticles, and discusses the design and application of NIR-Ⅱ emissive rare-earth nanoparticles according to the use of different sensitizers (Yb^(3+), Nd^(3+), Er^(3+) and Tm^(3+)). Finally, the limitations and development direction of rare-earth nanoparticles in NIR-Ⅱ imaging are prospected.