Indocyanine green (ICG) is a human compatible dye and is ideal for deep‐tissue two‐photon fluorescence (2PF) microscopy excited at the 1700‐nm window in vivo. However, the two‐photon excitation and emission properties of this dye remain unknown. Here we demonstrate measurement of the two‐photon excitation and emission properties of ICG in both water and human plasma, using home‐built two‐photon action cross‐sectional measurement and two‐photon emission spectrum measurement systems. Our results show that excited from 1600 to 1800 nm, 2PF can be generated from ICG dissolved in both water and human plasma. The measured two‐photon action cross‐sectional ησ₂ of ICG dissolved in human plasma is an order‐of‐magnitude larger than that dissolved in water. The measured two‐photon emission spectrum overlaps with the one‐photon emission spectrum for ICG dissolved in both human plasma and water. Our results will provide key two‐photon parameters for the clinical use of ICG.

中文翻译：

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在1700 nm窗口激发的水和人体血浆中吲哚菁绿的双光子性质的测量

吲哚菁绿（ICG）是一种与人类兼容的染料，非常适合在1700 nm窗口处在体内激发的深层组织双光子荧光（2PF）显微镜。但是，该染料的双光子激发和发射特性仍然未知。在这里，我们演示了使用自制的双光子作用横截面测量和双光子发射光谱测量系统测量ICG在水和人血浆中的双光子激发和发射特性。我们的结果表明，在水和人体血浆中溶解的ICG可以在1600至1800 nm的激发下生成2PF。所测量的双光子动作剖ησ ₂溶解在人血浆中的ICG的数量级比溶解在水中的ICG大一个数量级。测得的双光子发射光谱与溶解在人血浆和水中的ICG的单光子发射光谱重叠。我们的结果将为ICG的临床使用提供关键的两光子参数。