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Photoacoustic (PA) imaging is emerging as one of the important non‐invasive imaging techniques in biomedical research. Small molecule‐ second near‐infrared window (NIR‐II) PA dyes combined with imaging data can provide comprehensive and in‐depth in vivo physiological and pathological information. However, the NIR‐II PA dyes usually exhibit "always‐on" properties due to the lack of a readily optically tunable group, which hinders the further applications in vivo. Herein, a novel class of dyes GX have been designed and synthesized as an activatable NIR‐II PA platform, in which the absorption/emission wavelength of GX‐5 extends up to 1082/1360 nm. Importantly, the GX dyes have a strong tissue penetration depth and high‐resolution for the mouse vasculature structures in NIR‐II PA 3D imaging and high signal‐to‐noise ratio in NIR‐II fluorescence (FL) imaging. Furthermore, to demonstrate the applicability of GX dyes, the first NIR‐II PA probe GX‐5‐CO activated by carbon monoxide (CO) was engineered and employed to reveal the enhancement of the CO levels in the hypertensive mice by high‐contrast NIR‐II PA and FL imaging. We expect that many derivatives of GX dyes will be developed to afford versatile NIR‐II PA platforms for designing a wide variety activatable NIR‐II PA probes as biomedical tools. [ABSTRACT FROM AUTHOR]

As highly dynamic organelles, lysosomes are involved in various physiological processes. The viscosity of lysosomes plays critical roles in maintaining their normal physiological function and abnormal variations of viscosity are associated with many diseases. Monitoring the changes of lysosomal viscosity could contribute to understanding lysosome-related physiological and pathological processes. In this work, based on an indole fluorophore and fluorescent polymer, poly(2-hydroxyethyl methacrylate) (PHEM), a new polymeric fluorescent probe, In-PHEM, with dual responsive sites for tracking changes of lysosomal viscosity is presented. In-PHEM showed excellent fluorescence properties and high photostability. With this robust probe, the variation of the lysosomal viscosity in cells under different physiological conditions, including inducer stimulation, the process of starvation and apoptosis, was monitored using dual-channel imaging. Therefore, this work may provide a powerful tool for monitoring changes of lysosomal viscosity and helping to understand the relationship between the viscosity changes of lysosomes and their related diseases. [ABSTRACT FROM AUTHOR]

The intensive investigation of chemodynamic therapy (CDT) for tumor eradication revealed that the therapeutic effects of this ROS-mediated therapy are limited by endogenous reductants and inefficient Fenton-like reactions. In this study, we developed a new Fe/Cu–AuNP–PEG nanocomposite to enhance CDT and provide a synergistic treatment for tumors. The Fe/Cu–AuNP–PEG nanocomposite demonstrated effective ˙OH production and high photothermal conversion efficiency under 808 nm illumination, which promoted the ˙OH production, thereby enhancing the CDT efficacy and exhibiting a synergistic treatment for cancer. More importantly, the Fe/Cu–AuNP–PEG nanocomposite showed the ability to deplete GSH and catalyze glucose to generate H2O2, which facilitated the Fenton-like reaction and reduced the antioxidant properties of tumors, further improving the efficacy of CDT. Therefore, the Fe/Cu–AuNP–PEG nanocomposite, with horseradish peroxidase-like, glutathione peroxidase-like, and glucose oxidase-like activities, is a promising anti-tumor agent for integrating enhanced CDT and photothermal therapy (PTT) with the enhancement of synergistic therapeutic effects. [ABSTRACT FROM AUTHOR]