Infrared vibrational spectroscopy has long been a powerful tool in biological imaging, promising detailed molecular insights without inflicting any damage on the sample. Now, an exciting leap forward has emerged from a collaboration between Helmholtz-Zentrum Berlin (HZB) and Humboldt University Berlin, employing this technology to explore living animal cells in their native liquid environments with unprecedented nanoscale resolution. This advancement leverages the infrared scattering-type scanning near-field optical microscope, or s-SNOM, integrated with the brilliance of the IRIS beamline at the BESSY II synchrotron source, inaugurating a new era of molecular imaging that combines spatial precision and biological relevance.
Understanding molecular compositions inside living cells has always been a complex task. Traditional infrared spectroscopy, while sensitive to molecular vibrations, suffers from limited spatial resolution and difficulty in analyzing samples in their native, often aqueous, conditions. The use of s-SNOM technology circumvents these limitations by enabling near-field detection of vibrational signals with spatial resolution down to 10 nanometers. Crucially, this study demonstrates the feasibility of applying nano-IR imaging directly to cells immersed in liquid, unlocking the door to observing cellular components in a state closer to their natural physiological environment.
Central to this breakthrough is the use of a highly transparent ultra-thin silicon carbide (SiC) membrane that supports cells during imaging. This biocompatible membrane serves a dual role: it preserves the viability and integrity of fibroblast cells during measurement and allows infrared light to pass through with minimal interference. This innovation enables the s-SNOM tip to probe vibrational spectra effectively through the liquid medium surrounding the cells, a feat previously hampered by the absorbing properties of water in the infrared range.
The team chose fibroblasts—cells pivotal in connective tissue formation and collagen production—as their biological model. These cells were cultured directly on the SiC membrane and imaged live in their liquid culture medium, providing an authentic snapshot of cellular molecular architecture. Infrared vibrational signatures were collected from key biomolecules, including proteins, nucleic acids, carbohydrates, and membrane lipids. These spectroscopic fingerprints allowed identification and mapping at distinct intracellular locations with nanometer precision.
One of the most striking outcomes of this approach was the ability to visualize subcellular structures such as the nucleus and various organelles without any fluorescent labeling or invasive markers. The spatial heterogeneity observed in the IR images corresponded well with known cell biology, reaffirming the accuracy of nano-IR vibrational spectroscopy in mapping biochemical complexity. This label-free modality offers the advantage of preserving cell viability and avoiding photobleaching effects common in fluorescence microscopy.
Beyond two-dimensional imaging, the research team explored how adjustable measurement parameters could modulate the probing depth of the infrared light scattered by the s-SNOM tip. By systematically varying these parameters, they gleaned depth-resolved molecular information, laying groundwork for infrared nano-tomography—a three-dimensional visualization technique that could revolutionize understanding of cell structure and function at the nanoscale. The prospect of reconstructing volumetric maps of molecular distributions inside live cells with such high resolution is tantalizing.
The robust vibrational signatures detected in the living cell environment herald exciting opportunities to study molecular interactions and dynamic processes in situ. Unlike electron microscopy or X-ray techniques, which require fixed or frozen samples, this method preserves biological activity, opening avenues for real-time investigations of cellular responses to stimuli, drug interactions, or pathological changes. The ability to analyze liquid-solid interfaces with such fine granularity broadens its potential in biointerface science and nanomaterials research.
Importantly, this study underscores the versatility of the IRIS beamline at BESSY II. Its extremely broadband, intense infrared light source provides the foundation for generating high signal-to-noise vibrational spectra essential for s-SNOM imaging. The integration of advanced infrared optics and sample handling strategies at this facility positions it at the forefront of nanoscale bio-imaging research, offering national and international users access to groundbreaking methodologies.
Researchers envision the application spectrum of this technology expanding rapidly. By adapting the system, different cell types—including various cancer cells—could be examined under native conditions, potentially revealing subtle molecular alterations associated with disease progression. This may illuminate pathways for diagnostic development or novel therapeutic targets, emphasizing the clinical relevance of nano-infrared vibrational spectroscopy.
The implications extend beyond biology. The ability to characterize molecular compositions and interactions at liquid-solid interfaces with nanometer resolution may significantly impact fields ranging from catalysis and energy materials to sensor development. The adaptability of s-SNOM coupled with synchrotron IR sources renders it a versatile platform for a wide array of scientific inquiries demanding high-fidelity nanoscale chemical mapping.
In sum, the intersection of nano-infrared vibrational spectroscopy with innovative sample support and synchrotron infrared light sources has culminated in a powerful new imaging modality. This approach not only surmounts longstanding challenges of imaging live cells in aqueous environments but also ushers in the possibility of detailed 3D molecular tomography at the nanoscale. As this technique evolves and gains wider adoption, it stands poised to unlock profound insights into cellular and molecular processes fundamental to life sciences and beyond.
The research article detailing these advances is published in the journal Small, highlighting the experimental validation and showcasing the capabilities of nano-IR imaging on living fibroblast cells. This transformative method is now accessible to the global scientific community through the IRIS beamline at BESSY II, signaling a new horizon for nanoscale vibrational spectroscopy and imaging.
Subject of Research: Lab-produced tissue samples
Article Title: Nano-infrared imaging and spectroscopy of animal cells in liquid environment
News Publication Date: 14-Oct-2025
Web References: 10.1002/smll.202507097
Image Credits: A. Veber/HZB
Keywords: Cell biology, infrared spectroscopy, nano-IR, s-SNOM, live-cell imaging, molecular vibrations, nanoscopy, fibroblast cells, silicon carbide membrane, IRIS beamline, BESSY II, nano-tomography
