Infrared Near-Field Microscopy as a Platform for Nanoscale Biomedical Spectroscopy and Imaging

Precision medicine requires tools that can resolve molecular information at the nanoscale, where many early biological and pathological changes arise. Scanning near-field optical microscopy (SNOM) combines molecular vibrational fingerprints with nanoscale spatial resolution, providing a unique platform for overcoming the diffraction limit of conventional optics and enabling in situ chemical characterization of biological samples. This paper systematically reviews the development of SNOM from near-field imaging to spectroscopic platforms such as nano-FTIR and AFM-IR, and summarizes the latest advances in ultrafast, liquid-phase, terahertz, and miniaturized systems. Focusing on representative studies involving proteins, nucleic acids, bacteria, viruses, extracellular vesicles, and cell-material interfaces, this paper discusses SNOM's ability to resolve molecular heterogeneity, structural transitions, and local biochemical interactions in near-natural environments. Additionally, the article analyzes the major challenges facing its clinical translation, including sample preparation, signal-to-noise ratio, measurement speed, quantitative analysis, and standardization, and explores its application potential in AI-assisted analysis, portability, and neuroscience. SNOM is expected to become a key technological platform bridging molecular diagnostics and nanobiological imaging.