Oxyhaemoglobin saturation NIR-IIb imaging for assessing cancer metabolism and predicting the response to immunotherapy.

In vivo quantitative assessment of oxyhaemoglobin saturation (sO) status in tumour-associated vessels could provide insights into cancer metabolism and behaviour. Here we develop a non-invasive in vivo sO imaging technique to visualize the sO levels of healthy and tumour tissue based on photoluminescence bioimaging in the near-infrared IIb (NIR-IIb; 1,500-1,700 nm) window. Real-time dynamic sO imaging with a high frame rate (33 Hz) reveals the cerebral arteries and veins through intact mouse scalp/skull, and this imaging is consistent with the haemodynamic analysis results. Utilizing our non-invasive sO imaging, the tumour-associated-vessel sO levels of various cancer models are evaluated. A positive correlation between the tumour-associated-vessel sO levels and the basal oxygen consumption rate of corresponding cancer cells at the early stages of tumorigenesis suggests that cancer cells modulate the tumour metabolic microenvironment. We also find that a positive therapeutic response to the checkpoint blockade cancer immunotherapy could lead to a dramatic decrease of the tumour-associated-vessel sO levels. Two-plex dynamic NIR-IIb imaging can be used to simultaneously observe tumour-vessel sO and PD-L1, allowing a more accurate prediction of immunotherapy response.