Lagarto João L, Credi Caterina, Villa Federica, Tisa Simone, Zappa Franco, Shcheslavskiy Vladislav, Saverio Pavone Francesco, Cicchi Riccardo
National Institute of Optics, National Research Council (INO-CNR), Via Nello Carrara 1, 50019 Sesto Fiorentino, Italy.
European Laboratory for Non-linear Spectroscopy (LENS), Via Nello Carrara 1, 50019 Sesto Fiorentino, Italy.
Sensors (Basel). 2019 Jun 13;19(12):2678. doi: 10.3390/s19122678.
Single Photon Avalanche Diode (SPAD) arrays are increasingly exploited and have demonstrated potential in biochemical and biomedical research, both for imaging and single-point spectroscopy applications. In this study, we explore the application of SPADs together with fiber-optic-based delivery and collection geometry to realize fast and simultaneous single-point time-, spectral-, and depth-resolved fluorescence measurements at 375 nm excitation light. Spectral information is encoded across the columns of the array through grating-based dispersion, while depth information is encoded across the rows thanks to a linear arrangement of probe collecting fibers. The initial characterization and validation were realized against layered fluorescent agarose-based phantoms. To verify the practicality and feasibility of this approach in biological specimens, we measured the fluorescence signature of formalin-fixed rabbit aorta samples derived from an animal model of atherosclerosis. The initial results demonstrate that this detection configuration can report fluorescence spectral and lifetime contrast originating at different depths within the specimens. We believe that our optical scheme, based on SPAD array detectors and fiber-optic probes, constitute a powerful and versatile approach for the deployment of multidimensional fluorescence spectroscopy in clinical applications where information from deeper tissue layers is important for diagnosis.
单光子雪崩二极管（SPAD）阵列正越来越多地得到应用，并已在生化和生物医学研究中展现出在成像及单点光谱应用方面的潜力。在本研究中，我们探索了将SPAD与基于光纤的传输和收集结构相结合的应用，以实现在375 nm激发光下快速且同时进行单点时间分辨、光谱分辨和深度分辨荧光测量。光谱信息通过基于光栅的色散在阵列的列间编码，而深度信息则由于探测收集光纤的线性排列在行间编码。最初的表征和验证是针对基于分层荧光琼脂糖的模型进行的。为了验证该方法在生物样本中的实用性和可行性，我们测量了来自动脉粥样硬化动物模型的福尔马林固定兔主动脉样本的荧光特征。初步结果表明，这种检测配置能够报告源自样本内不同深度的荧光光谱和寿命对比度。我们相信，我们基于SPAD阵列探测器和光纤探头的光学方案，构成了一种强大且通用的方法，可用于在临床应用中部署多维荧光光谱，在这些应用中，来自更深组织层的信息对诊断很重要。
