Nitric oxide (NO), a pivotal signalling molecule, plays multifaceted roles in physiological and pathological processes, including cardiovascular and immune functions, neurotransmission and cancer progression. Nevertheless, measuring NO in vivo is challenging due to its transient nature and the complexity of the biological environment. Here we describe NO-responsive magnetic probes made of crosslinked superparamagnetic iron oxide nanoparticles tethered to a NO-sensitive cleavable linker for highly sensitive and selective NO magnetic resonance imaging in vivo. These probes enable the detection of NO at concentrations as low as 0.147 μM, allowing for the imaging and quantification of NO in mouse tumour models, studying its effects on tumour progression and immunity and assessing the response of tumour-associated macrophages to cancer immunotherapeutic agents. Additionally, they facilitate concurrent anatomical and molecular imaging of organs, helping to identify pathological alterations in the liver. Overall, these probes represent promising non-invasive tools for investigating the dose-dependent conflicting role of NO in physiological and pathophysiological processes.

一氧化氮 （NO） 是一种关键的信号分子，在生理和病理过程中发挥着多方面的作用，包括心血管和免疫功能、神经传递和癌症进展。然而，由于其瞬时性和生物环境的复杂性，体内测量 NO 具有挑战性。在这里，我们描述了由交联超顺磁性氧化铁纳米颗粒制成的 NO 响应性磁性探针，这些纳米颗粒与 NO 敏感的可切割接头相连，用于体内高灵敏度和选择性的 NO 磁共振成像。这些探针能够检测浓度低至 0.147 μM 的 NO，从而可以在小鼠肿瘤模型中对 NO 进行成像和定量，研究其对肿瘤进展和免疫的影响，并评估肿瘤相关巨噬细胞对癌症免疫治疗剂的反应。此外，它们还有助于器官的同步解剖和分子成像，有助于识别肝脏的病理改变。总体而言，这些探针代表了有前途的非侵入性工具，用于研究 NO 在生理和病理生理过程中的剂量依赖性冲突作用。