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Hydroxyl radical (•OH), a highly reactive oxygen species (ROS), is assumed as one of the most aggressive free radicals. This radical has a detrimental impact on cells as it can react with different biological substrates leading to pathophysiological disorders, including inflammation, mitochondrion dysfunction, and cancer. Quantification of this free radical in‐situ plays critical roles in early diagnosis and treatment monitoring of various disorders, like macrophage polarization and tumor cell development. Luminescence analysis using responsive probes has been an emerging and reliable technique for in‐situ detection of various cellular ROS, and some recently developed •OH responsive nanoprobes have confirmed the association with cancer development. This paper aims to summarize the recent advances in the characterization of •OH in living organisms using responsive nanoprobes, covering the production, the sources of •OH, and biological function, especially in the development of related diseases followed by the discussion of luminescence nanoprobes for •OH detection. [ABSTRACT FROM AUTHOR]

Cancer detection and inflammation monitoring during photothermal therapy (PTT) enable timely cancer intervention and precise inflammation control, advancing to address inflammation‐related tumor recurrence and metastasis associated with PTT. This can be achieved through real‐time monitoring biomarker for cancer and inflammation, like hypochlorous acid (HOCl), a highly reactive oxygen species (hROS) in body with elevated levels in inflammation. Here, a HOCl‐responsive theranostic nanoprobe is introduced, AuNRs@SiO2‐CAA for ratiometric photoacoustic (PA) cancer detection and inflammation monitoring during PTT. AuNRs@SiO2‐CAA emits PA signals at 680 and 820 nm, with only PA680 undergoing changes in the presence of HOCl, enabling precise HOCl imaging via recording changes of ratiometric PA signals (PA680/PA820). AuNRs@SiO2‐CAA exhibits high selectivity and sensitivity, with a detection limit of 0.34 µM for ratiometric PA imaging of HOCl. In vivo, it effectively detects tumor, drives PTT, and monitors inflammation during PTT by sensing HOCl. The successful development of AuNRs@SiO2‐CAA offers a novel theranostic nanoprobe system for cancer diagnosis, poised to enhance PTT through precise inflammation control. [ABSTRACT FROM AUTHOR]

Quantification of hydroxyl radicals (˙OH), one form of reactive oxygen species (ROS), plays critical roles in early diagnosis and treatment monitoring of various diseases. In this work, we report the development of a responsive nanoprobe for ratiometric fluorescence detection and imaging of ˙OH in macrophage polarization. The nanoprobe, BSA-CCA@LDH-SRB, was designed and prepared using coumarin 3-carboxylic acid (CCA) as the sensing unit for ˙OH, and sulforhodamine B (SRB) loaded on layered double hydroxide (LDH) served as the fluorescent reference component. The coupling of CCA to bovine serum albumin (BSA) and the loading of BSA-CCA on the surface of LDH enabled the nanoprobe for fluorescence detection of ˙OH with high sensitivity and minimal interference from other biomolecules, ions, and ROS. The emission of the prepared BSA-CCA@LDH-SRB at 444 nm emerged and the intensity was increased according to the concentration of ˙OH, while the emission at 580 nm was maintained, allowing the nanoprobe for ratiometric fluorescence ( F 444/580 ) detection of ˙OH. Loading of the BSA protein on the LDH surface and the biocompatibility and colloidal stability of the LDH-based fluorescent nanoprobe were further improved, facilitating the detection of ˙OH generation in macrophage polarization stimulated by both biomolecules and physical ultrasound irradiation. This study thus offers a new nanoprobe as the tool for investigating ˙OH evolutions, advancing the biomedical investigations of macrophage polarization associated inflammation.