Small‐molecule‐based second near‐infrared (NIR‐II) activatable fluorescent probes can potentially provide a high target‐to‐background ratio and deep tissue penetration. However, most of the reported NIR‐II activatable small‐molecule probes exhibit poor versatility owing to the lack of a general and stable optically tunable group. In this study, we designed NIRII‐HDs, a novel dye scaffold optimized for NIR‐II probe development. In particular, dye NIRII‐HD5 showed the best optical properties such as proper pKa value, excellent stability, and high NIR‐II brightness, which can be beneficial for in vivo imaging with high contrast. To demonstrate the applicability of the NIRII‐HD5 dye, we designed three target‐activatable NIR‐II probes for ROS, thiols, and enzymes. Using these novel probes, we not only realized reliable NIR‐II imaging of different diseases in mouse models but also evaluated the redox potential of liver tissue during a liver injury in vivo with high fidelity.

The second near-infrared (NIR-II) fluorescent imaging shows great potential for deep tissue analysis at high resolution in living body owing to low background autofluorescence and photon scattering. However, reversible monitoring of redox homeostasis using NIR-II fluorescent imaging remains a challenge due to the lack of appropriate probes. In this study, a series of stable and multifunctional NIR-II dyes (NIR-II Cy3s) were constructed based on trimethine skeleton. Significantly, introducing the 1,4-diethyl-decahydroquinoxaline group to the NIR-II Cy3s not only effectively increased the wavelength, but also served as an effective response site for HClO, which can be restored by reactive sulfur species (RSS). Based on this, NIR-II Cy3s were used for reversible monitoring of HClO/RSS-mediated redox processes in the pathophysiology environment. Finally, NIR-II Cy3-988 was successfully utilized for assessment of the redox environments and drug treatment effects in acute inflammation model.

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Small‐molecule‐based second near‐infrared (NIR‐II) activatable fluorescent probes can potentially provide a high target‐to‐background ratio and deep tissue penetration. However, most of the reported NIR‐II activatable small‐molecule probes exhibit poor versatility owing to the lack of a general and stable optically tunable group. In this study, we designed NIRII‐HDs, a novel dye scaffold optimized for NIR‐II probe development. In particular, dye NIRII‐HD5 showed the best optical properties such as proper pKa value, excellent stability, and high NIR‐II brightness, which can be beneficial for in vivo imaging with high contrast. To demonstrate the applicability of the NIRII‐HD5 dye, we designed three target‐activatable NIR‐II probes for ROS, thiols, and enzymes. Using these novel probes, we not only realized reliable NIR‐II imaging of different diseases in mouse models but also evaluated the redox potential of liver tissue during a liver injury in vivo with high fidelity.

Bacterial infections can easily occur when patients mishandle wounds or eat moldy food. The prompt diagnosis of a bacterial infection could effectively reduce the risk of possible anatomical damage. However, non-invasive early detection of bacterial infections is difficult to achieve due to the lack of favorable tools. Here, we designed two hNQO1 fluorescent probes (RX2 and RX3) to visualize bacterial infection after deep learning on the pathogenesis of bacterial infection. RX2 and RX3 enable early detection of bacterial infection and are verified to be, respectively, suitable for fluorescence imaging (FLI) and photoacoustic imaging (PAI) by comparing the signal-to-background ratio of both probes in a mouse model of myositis caused by Escherichia coli infection. In view of the difference in penetration depth between the two imaging modalities, we further applied RX2 for FLI of E. coli-infected wounds and RX3 for PAI of E. coli-infected inflammatory bowel disease, suggesting the great potential of both probes for early diagnosis of bacterial infections.

The second near-infrared (NIR-II) fluorescent imaging shows great potential for deep tissue analysis at high resolution in living body owing to low background autofluorescence and photon scattering. However, reversible monitoring of redox homeostasis using NIR-II fluorescent imaging remains a challenge due to the lack of appropriate probes. In this study, a series of stable and multifunctional NIR-II dyes (NIR-II Cy3s) were constructed based on trimethine skeleton. Significantly, introducing the 1,4-diethyl-decahydroquinoxaline group to the NIR-II Cy3s not only effectively increased the wavelength, but also served as an effective response site for HClO, which can be restored by reactive sulfur species (RSS). Based on this, NIR-II Cy3s were used for reversible monitoring of HClO/RSS-mediated redox processes in the pathophysiology environment. Finally, NIR-II Cy3-988 was successfully utilized for assessment of the redox environments and drug treatment effects in acute inflammation model.