Near-Infrared Imaging Techniques for Biomedical Applications

Near-infrared (NIR) imaging has emerged as a pivotal tool in biomedicine, offering non-invasive visualization with enhanced tissue penetration and reduced background interference. Conventional fluorescence methods operating in the first near-infrared window (NIR-I, 700–900 nm) laid the groundwork for in vivo studies by mitigating visible-light absorption and scattering. The advent of the second near-infrared window (NIR-II, 1 000–1 700 nm) has further revolutionised deep-tissue imaging by exploiting the optical transparency of biological media at longer wavelengths, resulting in higher spatial resolution, deeper penetration depths and lower autofluorescence. A diversity of probes—including rare-earth down-conversion nanoparticles, organic nanofluorophores, quantum dots and bioluminescent constructs—have been tailored to this spectral region. Techniques such as wide-field fluorescence, confocal microscopy, light-sheet imaging and lifetime analysis enable dynamic tracking of vasculature, lymphatics, tumours and immune cells. The integration of energy-transfer strategies, multimodal contrast and stimulus-responsive elements expands functionality to image-guided surgery, drug-release monitoring and real-time assessment of cellular heterogeneity. Ongoing refinements in probe brightness, biocompatibility and clearance pathways continue to bridge preclinical demonstration and clinical translation, underscoring the global significance of NIR imaging for diagnostics, therapeutic monitoring and surgical navigation.

Research from Nature Portfolio

Recent studies have advanced NIR-IIb and NIR-II bioluminescent probes for deep-tissue tracking of immune responses and tumour metastases. Innovative polymer-coated down-conversion nanoparticles emitting at 1 500–1 700 nm enable non-invasive monitoring of vaccine distribution and T-cell migration with wide-field and lifetime imaging, demonstrating complete tumour eradication in murine models. Complementary developments in bioluminescence imaging have yielded ATP-responsive probes emitting at 1 029 nm, integrating bioluminescence resonance energy transfer (BRET) and fluorescence resonance energy transfer (FRET) to achieve fivefold improvements in signal-to-noise ratio and enabling high-contrast detection of metastatic sites. Moreover, bright organic nanofluorophores with emission beyond 1 100 nm have facilitated one-photon three-dimensional confocal imaging of vasculature in fixed tissue at depths exceeding 1.3 mm with sub-10 µm resolution, underscoring the potential for volumetric mapping of microcirculation.

Near-Infrared Imaging Techniques for Biomedical Applications publication trend

The graph below shows the total number of articles in near-infrared imaging techniques for biomedical applications across all publications each year (not limited to Nature Index journals).

Technical terms

Near-infrared I (NIR-I): Spectral region from 700 to 900 nm offering moderate penetration and reduced visible-light absorption.

Near-infrared II (NIR-II): Spectral window from 1 000 to 1 700 nm providing deeper tissue penetration and lower autofluorescence.

Down-conversion nanoparticle: A luminescent nanocrystal that absorbs shorter-wavelength light and emits at longer NIR wavelengths for deep-tissue imaging.

Bioluminescence resonance energy transfer (BRET): A mechanism that transfers energy from a bioluminescent donor to a fluorescent acceptor, enabling emission beyond the donor’s native wavelength.

Fluorescence resonance energy transfer (FRET): Energy transfer between two fluorophores in close proximity, used to enhance emission or sense molecular interactions.

Autofluorescence: Background fluorescence from endogenous biomolecules that can obscure signals from exogenous probes.

References

1. Shortwave-infrared-light-emitting probes for the in vivo tracking of cancer vaccines and the elicited immune responses. Nature Biomedical Engineering (2023).
2. Tracking tumor heterogeneity and progression with near‐infrared II fluorophores. Exploration (2023).
3. Boosting the down-shifting luminescence of rare-earth nanocrystals for biological imaging beyond 1500 nm. Nature Communications (2017).
4. A bright organic NIR-II nanofluorophore for three-dimensional imaging into biological tissues. Nature Communications (2018).
5. NIR-II nanoprobes in-vivo assembly to improve image-guided surgery for metastatic ovarian cancer. Nature Communications (2018).
6. In vivo gastrointestinal drug-release monitoring through second near-infrared window fluorescent bioimaging with orally delivered microcarriers. Nature Communications (2017).
7. NIR-II bioluminescence for in vivo high contrast imaging and in situ ATP-mediated metastases tracing. Nature Communications (2020).
8. Perfecting and extending the near-infrared imaging window. Light: Science & Applications (2021).
9. Recent Progress in NIR-II Contrast Agent for Biological Imaging. Frontiers in Bioengineering and Biotechnology (2020).
10. Highly Fluorescent Ribonuclease-A-Encapsulated Lead Sulfide Quantum Dots for Ultrasensitive Fluorescence in Vivo Imaging in the Second Near-Infrared Window. Chemistry of Materials (2016).
11. NIR-II fluorescence microscopic imaging of cortical vasculature in non-human primates. Theranostics (2020).