Institute of Cardiology, Lithuanian University of Health Sciences, Kaunas, Lithuania.
Sci Rep. 2017 Aug 11;7(1):7983. doi: 10.1038/s41598-017-08168-7.
Indocyanine green (ICG) fluorescent dye has been approved by the FDA for use in medical diagnostics. Recently, we demonstrated that ICG dye has voltage-sensitive properties with a dual-component (fast and slow) response in the Langendorff-perfused rabbit heart. Here, we extended our studies by showing the different spectral properties of both components for analysis of the fractional change in ICG fluorescence in response to voltage changes. We used light from four LEDs to obtain excitation; emission was measured using an EMCCD camera with band-pass filters and a spectrometer. We applied a graphical model with Gaussian functions to construct and evaluate the individual emission curves and calculated the voltage-sensitive portion of each component of the ICG fluorescence in the rabbit heart. The results revealed that each isolated component (fast and slow) emanates from a unique ICG pool in a different environment within the cell membrane and that each component is also composed of two constituents (ICG-monomeric and ICG-aggregated). We propose the existence of different voltage-sensitive mechanisms for the components: (I) electrochromism and field-induced reorientation for the fast component; and (II) field-induced dye squeezing that amplifies intermolecular interactions, resulting in self-quenching of the dye fluorescence, for the slow component.
吲哚菁绿（ICG）荧光染料已获得 FDA 批准用于医学诊断。最近，我们证明了 ICG 染料具有电压敏感性，在 Langendorff 灌注兔心中表现出双组分（快速和缓慢）响应。在这里，我们通过显示两个组件的不同光谱特性来扩展我们的研究，以分析 ICG 荧光对电压变化的分数变化。我们使用四个 LED 发出的光进行激发；使用具有带通滤波器和光谱仪的 EMCCD 相机测量发射。我们应用具有高斯函数的图形模型来构建和评估单个发射曲线，并计算兔心中 ICG 荧光的每个组件的电压敏感部分。结果表明，每个分离的组件（快速和缓慢）都从细胞膜内不同环境中的独特 ICG 池中发出，并且每个组件还由两个组成部分（ICG-单体和 ICG-聚集）组成。我们提出了组件的不同电压敏感机制的存在：（I）快速组件的电致变色和场诱导重定向；以及（II）场诱导染料挤压，放大分子间相互作用，导致染料荧光自猝灭，对于缓慢组件。
