Oxygen tension at 50% haemoglobin saturation (P 50 ), which reflects the degree of peripheral oxygen offloading and tissue oxygenation, plays an important role in the diagnosis and treatment of disease, as well as in transfusion research. Blood gas analysers are commonly used in clinical and obtain P 50 values through complex calculations and analysis. Oxygenation-dissociation analysers are specially designed to record the oxygen dissociation curves and obtain P 50 values of whole blood, red blood cells (RBCs), and stroma-free haemoglobin. However, whether the two equipment obtain comparable data is still uncertain. Herein, we used both equipment to detect P 50 values of blood and stroma-free haemoglobin from human and bovine sources, venous and arterial blood of beagle and rat, and stored rat blood. For human blood, both analysers yielded similar data. P 50 of the stroma-free haemoglobin and bovine blood could only be properly detected by oxygenation-dissociation analysers. Blood gas analysers showed different P 50 values, while oxygenation-dissociation analysers got similar P 50 values for arterial and venous samples. Oxygenation-dissociation analysers distinguished changes in P 50 values during RBCs storage. Compared with the blood gas analysers, oxygenation-dissociation analysers had a stronger detection capability in P 50 measurement with regard to both sample types and species.

Introduction: High altitude-related hypoxia-induced organ damage significantly impacts people who are exposed to acute high-altitude environment. At present, kidney injury still lacks effective treatment strategies. Iridium nanozymes (Ir-NPs) are a nanomaterial with various enzymatic activities and are expected to be used in kidney injury treatment.Methods: In this study, we simulated a high-altitude environment (6000 m) to induce a kidney injury model, and explored the therapeutic effect of Ir-NPs in mice with kidney injury in this environment. Changes in the microbial community and metabolites were analyzed to explore the possible mechanism underlying the improvement of kidney injury during acute altitude hypoxia in mice treated with Ir-NPs.Results: It was discovered that plasma lactate dehydrogenase and urea nitrogen levels were considerably increased in mice exposed to acute altitude hypoxia compared to mice in a normal oxygen environment. Furthermore, there was a substantial increase in IL-6 expression levels in hypoxic mice; contrastingly, Ir-NPs decreased IL-6 expression levels, reduced the levels of succinic acid and indoxyl sulfate in the plasma and kidney pathological changes caused by acute altitude hypoxia. Microbiome analysis showed that bacteria, such as Lachnospiraceae_UCG_006 predominated in mice treated with Ir-NPs.Conclusion: Correlation analysis of the physiological, biochemical, metabolic, and microbiome-related parameters showed that Ir-NPs could reduce the inflammatory response and protect kidney function under acute altitude hypoxia, which may be related to intestinal flora distribution regulation and plasma metabolism in mice. Therefore, this study provides a novel therapeutic strategy for hypoxia-related kidney injury, which could be applied to other hypoxia-related diseases.

Hemoglobin-polydopamine particles (Hb-PDA) have shown high stability, with polydopamine (PDA) serving as a protective layer and antioxidant. However, the effects of the PDA coating on the properties and in vivo biosafety of Hb-PDA remain unclear. This work was conducted to characterize Hb-PDA and evaluate its biosafety. Hb-PDA exhibited negative surface charge and their infusion did not cause blood immunotoxicity or significant tissue injury. Hb-PDA were not phagocyted after co-incubation with macrophages for 3 h. Moreover, the particles showed the highest accumulation in the lungs, and a prolonged retention in major organs. It was also found that the particles were cleared by macrophages in splenic tissue and Kupffer cells in hepatic tissue. In summary, this research showed that Hb-PDA has high dispersion stability, low in vivo toxicity, and extended retention, illustrating its potency as a biosafe oxygen carrier.

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