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arXiv · 2603.05785

Mid-wave infrared photothermal microscopy for molecular and metabolic imaging in deep tissues and spheroids

Mingsheng Li·Yuhao Yuan·Guangrui Ding·Hongli Ni·Biwen Gao·Dashan Dong·Qinshu He·Hongjian He·Xinyan Teng·Yuwei Sun·Dingcheng Sun·Qing Xia·Thao Pham·Ji-Xin Cheng
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Abstract

High-resolution chemical imaging within deep tissues and intact spheroids remains a grand challenge. Here, we introduce mid-wave infrared photothermal (MWIP) microscopy operating in the underexplored 2000-2500 nm spectral window for submicron-resolution molecular and metabolic imaging in intact tumor spheroids and deep tissues. A dark-field photothermal detection scheme significantly suppresses water background and enhances contrast. By accessing strong carbon-hydrogen combination absorptions, a detection limit of 0.12% for dimethyl sulfoxide is achieved, comparable to stimulated Raman scattering microscopy. Depth-resolved imaging of endogenous biomolecules up to 500 micrometers in excised mouse skin and brain tissues is demonstrated. MWIP further enables depth-resolved tracking of transdermal drug transport via carbon-deuterium overtone absorption. Using deuterium metabolic probes, fatty-acid metabolism is imaged at 200 micrometers deep within intact tumor spheroids through carbon-deuterium overtone and combination bands. Collectively, MWIP offers a platform for functional imaging of 3D biological systems in their native environments.

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Mingsheng Li, Yuhao Yuan, Guangrui Ding, Hongli Ni, Biwen Gao, Dashan Dong, Qinshu He, Hongjian He, Xinyan Teng, Yuwei Sun, Dingcheng Sun, Qing Xia, Thao Pham, Ji-Xin Cheng. 2026-03-06. Mid-wave infrared photothermal microscopy for molecular and metabolic imaging in deep tissues and spheroids. https://arxiv.org/abs/2603.05785

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