Light scattering by biological tissues sets a limit to the penetration depth of high-resolution optical microscopy imaging of live mammals in vivo. An effective approach to reduce light scattering and increase imaging depth is to extend the excitation and emission wavelengths to the second near-infrared window (NIR-II) at >1,000 nm, also called the short-wavelength infrared window. Here we show biocompatible core–shell lead sulfide/cadmium sulfide quantum dots emitting at ~1,880 nm and superconducting nanowire single-photon detectors for single-photon detection up to 2,000 nm, enabling a one-photon excitation fluorescence imaging window in the 1,700–2,000 nm (NIR-IIc) range with 1,650 nm excitation—the longest one-photon excitation and emission for in vivo mouse imaging so far. Confocal fluorescence imaging in NIR-IIc reached an imaging depth of ~1,100 μm through an intact mouse head, and enabled non-invasive cellular-resolution imaging in the inguinal lymph nodes of mice without any surgery. We achieve in vivo molecular imaging of high endothelial venules with diameters as small as ~6.6 μm, as well as CD169 + macrophages and CD3 + T cells in the lymph nodes, opening the possibility of non-invasive intravital imaging of immune trafficking in lymph nodes at the single-cell/vessel-level longitudinally.

生物组织的光散射限制了活体哺乳动物体内高分辨率光学显微镜成像的穿透深度。减少光散射和增加成像深度的有效方法是将激发和发射波长扩展到 >1,000 nm 的第二个近红外窗口 (NIR-II)，也称为短波长红外窗口。在这里，我们展示了在 ~1,880 nm 发射的生物相容性核壳硫化铅/硫化镉量子点和超导纳米线单光子检测器，用于高达 2,000 nm 的单光子检测，使单光子激发荧光成像窗口在 1,700–2,000 nm (NIR-IIc) 范围，激发波长为 1,650 nm——迄今为止小鼠体内成像最长的单光子激发和发射。NIR-IIc 共聚焦荧光成像通过完整的小鼠头部达到约 1,100 μm 的成像深度，无需任何手术即可在小鼠腹股沟淋巴结中实现非侵入性细胞分辨率成像。我们实现了直径小至 ~6.6 μm 的高内皮微静脉以及淋巴结中的 CD169 + 巨噬细胞和 CD3 + T 细胞的体内分子成像，开启了淋巴结免疫运输的非侵入性活体成像的可能性在单细胞/血管水平纵向。