Xi Jiefeng, Chen Yongping, Li Xingde
Department of Biomedical Engineering, Johns Hopkins University, Baltimore, MD 21205, USA.
Biomed Opt Express. 2013 May 9;4(6):842-51. doi: 10.1364/BOE.4.000842. Print 2013 Jun 1.
We report a cross-referencing method to quickly and accurately characterize the optical properties of nanoparticles including the extinction, scattering, absorption and backscattering cross sections by using an OCT system alone. Among other applications, such a method is particularly useful for developing nanoparticle-based OCT imaging contrast agents. The method involves comparing two depth-dependent OCT intensity signals collected from two samples (with one having and the other not having the nanoparticles), to extract the extinction and backscattering coefficient, from which the absorption coefficient can be further deduced (with the help of the established scattering theories for predicting the ratio of the backscattering to total scattering cross section). The method has been experimentally validated using test nanoparticles and was then applied to characterizing gold nanocages. With the aid of this method, we were able to successfully synthesize scattering dominant gold nanocages for the first time and demonstrated the highest contrast enhancement ever achieved by the gold nanocages (and by any nanoparticles of a similar size and concentration) in an in vivo mouse tumor model. This method also enables quantitative analysis of contrast enhancement and provides a general guideline on choosing the optimal concentration and optical properties for the nanoparticle-based OCT contrast agents.
我们报告了一种交叉参考方法，通过单独使用光学相干断层扫描（OCT）系统来快速准确地表征纳米颗粒的光学特性，包括消光、散射、吸收和后向散射截面。在其他应用中，这种方法对于开发基于纳米颗粒的OCT成像造影剂特别有用。该方法包括比较从两个样品（一个含有纳米颗粒，另一个不含纳米颗粒）收集的两个深度相关的OCT强度信号，以提取消光系数和后向散射系数，进而可以推导出吸收系数（借助已建立的散射理论来预测后向散射与总散射截面的比率）。该方法已通过测试纳米颗粒进行了实验验证，然后应用于表征金纳米笼。借助这种方法，我们首次成功合成了以散射为主的金纳米笼，并在体内小鼠肿瘤模型中展示了金纳米笼（以及任何尺寸和浓度相似的纳米颗粒）所实现的最高对比度增强。这种方法还能够对对比度增强进行定量分析，并为选择基于纳米颗粒的OCT造影剂的最佳浓度和光学特性提供一般指导。
