Optical Oxygen Sensing Techniques in Biomedicine

Optical oxygen sensing has emerged as a pivotal tool in biomedical research, offering non-invasive, spatiotemporal measurements of oxygen distribution across scales ranging from single cells to intact tissues. Techniques based on luminescent and phosphorescent probes exploit the quenching of excited-state emission by molecular oxygen, enabling quantitative readouts via changes in intensity, lifetime or emission ratio. Advances in indicator chemistry have yielded nitrogen- and platinum-based porphyrins, iridium complexes and aza-BODIPY fluorophores that emit in the red to near-infrared region, minimising background autofluorescence and maximising tissue penetration. Integration with confocal, two-photon and wide-field microscopy has facilitated three-dimensional mapping of oxygen tension in live cell cultures, multicellular spheroids and microvascular networks. Complementary planar and fibre-optic sensor formats deliver point- or surface-resolved monitoring for applications in high-throughput screening, wound assessment and implantable devices. Recent developments emphasise ratiometric designs and lifetime imaging to circumvent artefacts due to probe concentration or photobleaching, while polymeric matrices and nanocarriers enhance biocompatibility and probe retention. Collectively, these innovations underpin new insights into cellular metabolism, tumour hypoxia, vascular function and therapeutic response, and define a versatile toolkit for both fundamental research and translational diagnostics.

Research from Nature Portfolio

High-resolution intracellular oxygen imaging has been realised through phosphorescence lifetime mapping within living cells. By combining a ubiquitous phosphorescent dye with a high-repetition-rate confocal lifetime microscope, it is now possible to visualise oxygen changes at subcellular resolution in both monolayer cultures and multicellular spheroids. This system captures reversible quenching of dye phosphorescence as cells transition from normoxia to anoxia, revealing oxygen depletion patterns that co-localise with mitochondria and respond dynamically to metabolic stimuli such as glucose. Improved spatial fidelity and reduced acquisition times enable successive monitoring of oxygen gradients during cellular activation, offering a powerful approach to interrogate physiological and pathological oxygen metabolism in real time.

Optical Oxygen Sensing Techniques in Biomedicine publication trend

The graph below shows the total number of articles in optical oxygen sensing techniques in biomedicine across all publications each year (not limited to Nature Index journals).

Technical terms

Phosphorescence lifetime: The average time an excited phosphorescent molecule remains in an excited state before emitting a photon; inversely related to local oxygen concentration.

Ratiometric sensing: A technique that measures the ratio of emissions from two fluorophores (one oxygen-sensitive, one reference), minimising errors from probe concentration or excitation intensity.

Luminescence quenching: The process by which molecular oxygen interacts with an excited luminophore, reducing its emission intensity or lifetime in proportion to oxygen concentration.

Two-photon phosphorescence lifetime microscopy (2PLM): An imaging modality that uses near-infrared excitation to excite phosphorescent probes via simultaneous absorption of two photons, enabling deeper tissue penetration and three-dimensional pO2 mapping.

Oxygen gradient: A spatial variation in oxygen concentration, often arising in three-dimensional cell cultures or tissues due to diffusion limitations and metabolic consumption.

References

1. Live Microscopy of Multicellular Spheroids with the Multimodal Near-Infrared Nanoparticles Reveals Differences in Oxygenation Gradients. ACS Nano (2024).
2. Optical methods for sensing and imaging oxygen: materials, spectroscopies and applications. Chemical Society Reviews (2014).
3. High resolution imaging of intracellular oxygen concentration by phosphorescence lifetime. Scientific Reports (2015).
4. Robust optical oxygen sensors based on polymer-bound NIR-emitting platinum( ii )–benzoporphyrins. Journal of Materials Chemistry C (2014).
5. Ratiometric Molecular Probes Based on Dual Emission of a Blue Fluorescent Coumarin and a Red Phosphorescent Cationic Iridium(III) Complex for Intracellular Oxygen Sensing. Sensors (2015).
6. Nanostructured Oxygen Sensor - Using Micelles to Incorporate a Hydrophobic Platinum Porphyrin. PLOS ONE (2012).
7. Three-dimensional mapping of oxygen tension in cortical arterioles before and after occlusion. Biomedical Optics Express (2013).