Mid-wave infrared photothermal microscopy for molecular and metabolic imaging in deep tissues and spheroids
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.
Keywords
Cite
@article{arxiv.2603.05785,
title = {Mid-wave infrared photothermal microscopy for molecular and metabolic imaging in deep tissues and spheroids},
author = {Mingsheng Li and Yuhao Yuan and Guangrui Ding and Hongli Ni and Biwen Gao and Dashan Dong and Qinshu He and Hongjian He and Xinyan Teng and Yuwei Sun and Dingcheng Sun and Qing Xia and Thao Pham and Ji-Xin Cheng},
journal= {arXiv preprint arXiv:2603.05785},
year = {2026}
}