Learning Articles
Author: Eleni Vomhof
Published: 21 Oct 2026 · Last updated: 21 Oct 2026
SWIR spectroscopy is a powerful tool for characterising functionalised molecules, biosensors, and biomarkers used in biomedical research. By combining sensitive detection in the second near-infrared window (NIR-II, ~1000-1700 nm) with techniques such as fluorescence and Raman spectroscopy, researchers can investigate molecular interactions, probe biological processes, and extract clinically relevant information from complex samples. This article highlights three recent studies that demonstrate the breadth of SWIR-enabled characterisation: an NIR-II carbon nanotube biosensor for detecting amyloid beta associated with Alzheimer's disease, a mechanistic study revealing how carbon nanotube biosensors generate optical signals, and a label-free Raman approach for assessing breast tumour margins during surgery. In addition, the article discusses measurement considerations that influence the choice of SWIR spectroscopy detectors and spectrograph configuration. Together, these examples illustrate how advanced spectroscopy in the NIR-II/SWIR region supports biomarker development, biosensor optimisation, and biomedical diagnostics.
New and improved biosensors and biomarkers form the basis for developing next-generation clinical tools required for in situ and in vivo medical diagnostics, cancer and disease screening, image-guided surgery, and targeted drug delivery. Key research targets include functionalised carbon nanotubes, biocompatible quantum dots, molecular fluorophores, biosensors, targeted drug carriers, and disease-specific biomarkers that emit in the second near-infrared window (NIR-II, ~1000-1700 nm). Compared to approaches using shorter wavelengths, these SWIR-active probes offer improved sensitivity for biological imaging due to deeper tissue penetration, reduced light scattering, and lower background autofluorescence.
Accurate characterisation is essential because the optical response of a functionalised molecule or biomarker is closely linked to its chemical composition, surface chemistry, structural integrity, and interactions with complex biological environments. Understanding these relationships helps researchers optimise probe performance and biocompatibility, and support the translation of new diagnostic approaches into clinical use.
Short-wave infrared (SWIR) spectroscopy is a powerful analytical approach for characterising biosensors, biomarkers and functionalised molecules developed for biomedical research and clinical diagnostics. A range of complementary spectroscopy techniques can be used to characterise these materials. SWIR fluorescence and photoluminescence spectroscopy are particularly valuable for evaluating emission characteristics, spectral signatures, quantum yield, photostability, and environment-dependent optical behaviour. Raman spectroscopy can provide information on chemical composition, functionalisation, and material quality, and can even detect intrinsic biochemical signatures without external labels. Reflectance and transmittance measurements can reveal absorption features and optical interactions relevant to sensing and imaging applications. Together, these techniques provide a comprehensive picture of the chemical, structural, and optical characteristics that determine the performance of SWIR-active biomarkers and functionalised molecules in biomedical research and clinical applications.
Short-Wave Infrared (SWIR) refers to the spectral region spanning ~1.0–2.5 µm. In practice, most SWIR imaging systems operate in the range of ~900–1700 nm, which corresponds to the sensitivity of standard InGaAs detectors. Extended SWIR systems push sensitivity up to ~2.2–2.5 µm by tuning InGaAs sensor stoichiometry and manufacturing processes.
In life sciences and biomedical applications, the second near-infrared window (NIR-II), also called the second biological window, is typically defined as ~1000–1700 nm. Compared to shorter wavelengths, NIR-II light can probe deeper into tissue with reduced scattering, while background autofluorescence is lower. This enables higher image contrast and more accurate molecular detection and diagnostics.
This article highlights recent research on biosensors and biomarkers and discusses measurement considerations that influence the choice of SWIR spectroscopy detectors and spectrograph configurations. The following studies illustrate how SWIR and NIR-II detection support:
Detecting and monitoring amyloid beta (Aβ) accumulation remain central challenges in Alzheimer's disease research. Toxic Aβ species can accumulate inside cells long before the plaques typically associated with disease progression become visible. New biosensors capable of detecting Aβ in living cells and organisms could support mechanistic studies of these early disease processes.
In this study, researchers developed a SWIR-emitting optical nanosensor based on single-walled carbon nanotubes (SWCNTs) functionalised with Aβ peptides [1]. This biosensor monitored Aβ accumulation in living cells and discriminated between healthy and Alzheimer's mouse brains in vivo.
Illustration of the Aβ sensing principle in Aβ-functionalised SWCNT nanosensors. Binding of amyloid beta (Aβ) to the nanotube surface alters the detected NIR-II fluorescence intensity and emission wavelength.
Using NIR-II fluorescence spectroscopy, the team showed that the functionalised nanotubes' fluorescence intensity and emission peak wavelength changed upon interacting with Aβ. The nanosensors were able to monitor Aβ accumulation in different neuronal and immune cell lines. After intracranial injection, they also differentiated between healthy and Alzheimer's disease mouse models. Using probes emitting in the NIR-II region was particularly beneficial for the in vivo experiments, as the increased penetration depth and low background fluorescence enabled imaging beyond the brain surface of live organisms.
For optical characterisation both in vitro and in vivo, the researchers employed SWIR fluorescence spectroscopy using Oxford Instruments' Shamrock spectrograph and iDus 1.7 μm InGaAs camera, allowing sensitive detection of SWIR emission from 723 to 1694 nm.
The work demonstrates how NIR-II biosensors can yield biological information that is difficult to obtain with conventional imaging techniques, particularly when probing dynamic molecular processes in complex tissue environments.
Original publication: Merav Antman-Passig, Eitan Wong, Georgia R. Frost, Christian Cupo, Janki Shah, Albert Agustinus, Ziyu Chen, Chiara Mancinelli, Maikel Kamel, Thomas Li, Lauren A. Jonas, Yue-Ming Li, Daniel A. Heller. Optical Nanosensor for Intracellular and Intracranial Detection of Amyloid-Beta. ACS Nano 16 (5): 7269–7283 (2022). https://doi.org/10.1021/acsnano.2c00054
For developing biosensors with improved performance, researchers need to understand the mechanisms of analyte detection and optical signal generation. This study investigated how the binding of target molecules to functionalised single-walled carbon nanotube (SWCNT) biosensors is converted into a detectable NIR-II fluorescence signal [2].
Illustration of SWCNT-based molecular sensors and the spectroscopy techniques used to study how molecular interactions are converted into optical signals. NIR fluorescence spectroscopy monitors the sensor response, while THz spectroscopy probes changes in the surrounding water environment. Reproduced from "Fluorescence changes in carbon nanotube sensors correlate with THz absorption of hydration", Nat. Commun. 15 (2024), by Sanjana S. Nalige, Phillip Galonska et al., licensed under CC BY 4.0.
The researchers investigated the NIR fluorescence changes in DNA-functionalised SWCNTs upon binding to the analytes dopamine and riboflavin. To uncover the sensing mechanism, they combined SWIR fluorescence spectroscopy with terahertz (THz) spectroscopy and molecular dynamics simulations. They discovered that changes in the SWCNTs' hydration layer upon analyte binding correlate directly with changes in fluorescence intensity. The results suggest that interactions of nanotube excitons with nearby water molecules play a central role in determining sensor response.
NIR-II fluorescence measurements were performed using an Oxford Instruments Kymera 193i spectrograph and iDus InGaAs 491 detector, allowing sensitive detection of subtle fluorescence changes associated with analyte binding.
The study provides insights into how SWCNT biosensors convert molecular interactions into optical signals, which can help design and optimise new biosensors.
Original publication: Nalige, S.S., Galonska, P., Kelich, P. et al. Fluorescence changes in carbon nanotube sensors correlate with THz absorption of hydration. Nat. Commun. 15, 6770 (2024). https://doi.org/10.1038/s41467-024-50968-9
Accurately defining tumour margins during breast-conserving surgery remains a significant clinical challenge. If the cancerous tissue is not removed completely, patients may require additional surgery. At the same time, surgeons aim to remove as little healthy tissue as possible. Fast and reliable methods for identifying tumour boundaries can help surgeons make decisions directly in the operating room and improve the outcome for patients.
In this study, researchers used Raman spectroscopy to distinguish healthy from cancerous breast tissue based on biochemical composition [3]. Rather than relying on fluorescent labels or contrast agents, the method measured intrinsic molecular signals from lipids, proteins and water within the tissue.
High-wavenumber Raman spectroscopy for distinguishing healthy and tumour breast tissue. Illustration of the experimental setup (left). Mean Raman spectra and standard deviations of healthy and tumour tissue confirmed by histopathology (right). Cancerous and healthy tissue show spectral differences associated with water, lipid and protein content. Adapted from Figures 1 and 3a of "High wavenumber Raman spectroscopy for intraoperative assessment of breast tumour margins", Analyst 148 (2023), by Jennifer Haskell et al., licensed under CC BY 4.0.
Using high-wavenumber Raman spectroscopy, where the Raman-scattered photons were detected in the NIR-II region, the team investigated freshly excised human breast tissue. The technique enabled rapid differentiation between healthy and cancerous tissue based on differences in water, lipid, and protein content. The analysis showed good agreement with conventional histopathology results.
For the Raman characterisation, the researchers used a homebuilt handheld probe coupled to a spectrometer equipped with an Oxford Instruments iDus InGaAs camera. The detector's high sensitivity was crucial for detecting the high-wavenumber Raman signals in the NIR-II range from the tissue fast enough for rapid molecular classification.
The work demonstrates how Raman spectroscopy can provide clinically relevant information from intrinsic tissue biomarkers. The approach has potential as an intraoperative tool for guiding surgical decision-making for precise cancer removal and tissue conservation.
Original publication: Jennifer Haskell, Thomas Hubbard, Claire Murray, Benjamin Gardner, Charlotte Ives, Douglas Ferguson, Nick Stone. High wavenumber Raman spectroscopy for intraoperative assessment of breast tumour margins. Analyst 148 (18): 4373–4385 (2023). https://doi.org/10.1039/d3an00574g
Different SWIR spectroscopy applications place different demands on instrumentation. Some experiments focus on detecting extremely weak fluorescence, photoluminescence or Raman signals, where maximising sensitivity and minimising noise are critical. Other workflows require high-throughput measurements, rapid acquisition of dynamic processes, or collection of spatially resolved spectral information. Choosing the most suitable instrumentation therefore depends not only on wavelength range, but also on the type of information required from the measurement.
The applications highlighted above ranged from biomarker sensing to tumour diagnostics, but the studies shared the requirement of detecting optical signals in the NIR-II region with high sensitivity and spectral resolution for revealing the relevant biological information. They relied on Oxford Instruments' iDus InGaAs cameras, which provide sensitive detection across the NIR-II/SWIR region for low-light spectroscopy applications. Their low dark current during long integrations enables detection of weak signals in fluorescence and Raman spectroscopy experiments.
Some research questions benefit from adding spatial or temporal information to spectroscopic measurements. Approaches such as hyperspectral imaging, multitrack spectroscopy, and back focal plane imaging can reveal how molecular signatures vary across cells, tissues or materials. Rapid acquisition rates are valuable for studying dynamic biological processes and for high-throughput screening. Oxford Instruments' C-RED 2 for spectroscopy complements traditional spectroscopic detectors by combining SWIR sensitivity with high frame rates and a two-dimensional sensor format. This allows a single detector to support both spectroscopy and imaging experiments, and enables fast, spatially resolved measurements.
A high-performance spectroscopic system requires not only a sensitive detector, but also a high-quality spectrograph. Oxford Instruments' Shamrock and Kymera spectrographs provide high-throughput configurable platforms for photoluminescence, Raman, absorption and emission spectroscopy. Their modular architecture allows researchers to combine complementary diagnostic modalities within a single system and configure measurements across a broad wavelength range spanning the UV, visible, NIR and SWIR regions. Depending on experimental requirements, researchers can optimise the trade-off between spectral resolution and wavelength coverage for their individual applications.
Together, Oxford Instruments detectors and spectrographs support a wide range of SWIR spectroscopy applications. Selecting the appropriate detector and spectrograph combination helps researchers tailor their instrument for the challenge of their experiments, and obtain comprehensive information from their biological samples and functionalised materials.
SWIR spectroscopy provides researchers with powerful tools for characterising functionalised molecules, biomarkers, and biosensors. The examples presented in this article demonstrate how techniques operating in the NIR-II/SWIR region can address different challenges, from detecting disease-associated biomolecules and understanding biosensor mechanisms, to identifying cancerous tissue through intrinsic biomarkers. Selecting the appropriate combination of detector and spectrograph for the respective experimental requirements is crucial for obtaining deep insight into molecular structure, function, and biological behaviour. As new biomarkers, biosensors, and imaging agents continue to emerge, SWIR spectroscopy will play an important role in their development, validation, and translation toward biomedical and clinical applications.
[1] Merav Antman-Passig, Eitan Wong, Georgia R. Frost, Christian Cupo, Janki Shah, Albert Agustinus, Ziyu Chen, Chiara Mancinelli, Maikel Kamel, Thomas Li, Lauren A. Jonas, Yue-Ming Li, Daniel A. Heller. Optical Nanosensor for Intracellular and Intracranial Detection of Amyloid-Beta. ACS Nano 16 (5): 7269–7283 (2022). https://doi.org/10.1021/acsnano.2c00054
[2] Nalige, S.S., Galonska, P., Kelich, P. et al. Fluorescence changes in carbon nanotube sensors correlate with THz absorption of hydration. Nat. Commun. 15, 6770 (2024). https://doi.org/10.1038/s41467-024-50968-9
[3] Jennifer Haskell, Thomas Hubbard, Claire Murray, Benjamin Gardner, Charlotte Ives, Douglas Ferguson, Nick Stone. High wavenumber Raman spectroscopy for intraoperative assessment of breast tumour margins. Analyst 148 (18): 4373–4385 (2023). https://doi.org/10.1039/d3an00574g
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