State Key Laboratory for Mechanical Behavior of Materials, School of Materials Science and Engineering, Xi'an Jiaotong University, Xi'an 710049, People's Republic of China.
The MOE Key Laboratory of Biomedical Information Engineering, School of Life Science and Technology, Xi'an Jiaotong University, Xi'an 710049, People's Republic of China.
Nanotechnology. 2017 Apr 28;28(17):175702. doi: 10.1088/1361-6528/aa6564. Epub 2017 Mar 30.
Fluorescent composite hydrogels have found widespread applications, especially in spatial and temporal monitoring of in vivo hydrogel behaviors via the emitting optical signal. However, most existing fluorescent composite hydrogels suffer from limited capability of deep tissue imaging and complicated fabrication routes. We herein report a facile method for fabricating fluorescent composite hydrogels based on the in situ synthesis of NaYF:Yb, Er upconversion nanoparticles (UCNPs). This approach employs polyacrylamide (PAAm) hydrogels as a template, where the interconnected pores within the hydrogel act as nanoreactors to confine the growth of nanocrystals. We then obtained a fluorescent composite hydrogel exhibiting upconversion fluorescence and enhanced mechanical properties. The fluorescence spectra show that the fluorescence intensity decreases with decreasing size of the UCNPs. We investigated the relationship between the optical properties of the fluorescent composite hydrogel and the incorporated UCNPs based on the morphology, size, and distribution of the UCNPs by using scanning electron microscopy and transmission electron microscopy. In addition, we demonstrated the applicability of the synthesized hydrogel for deep tissue imaging through an in vitro tissue penetration experiment. Compressive and dynamic rheological testing reveal enhanced mechanical properties with increasing UCNP concentration. The fabricated upconversion fluorescent composite hydrogel may pave the way for monitoring the in vivo behavior of biomimetic materials via deep tissue imaging.
荧光复合水凝胶具有广泛的应用，特别是在通过发射光学信号对体内水凝胶行为进行时空监测方面。然而，大多数现有的荧光复合水凝胶在深层组织成像方面的能力有限，且制造工艺复杂。本文报告了一种基于原位合成 NaYF:Yb,Er 上转换纳米粒子（UCNPs）制备荧光复合水凝胶的简便方法。该方法采用聚丙烯酰胺（PAAm）水凝胶作为模板，水凝胶内的相互连通的孔作为纳米反应器来限制纳米晶体的生长。然后，我们获得了一种具有上转换荧光和增强机械性能的荧光复合水凝胶。荧光光谱表明，荧光强度随 UCNPs 尺寸的减小而降低。我们通过扫描电子显微镜和透射电子显微镜研究了荧光复合水凝胶的光学性质与所掺入的 UCNPs 之间的关系，包括 UCNPs 的形态、尺寸和分布。此外，我们通过体外组织穿透实验证明了所合成的水凝胶在深层组织成像中的适用性。压缩和动态流变学测试表明，随着 UCNP 浓度的增加，机械性能得到增强。所制备的上转换荧光复合水凝胶可能为通过深层组织成像监测仿生材料的体内行为铺平道路。
