Self‐Immobilizing Fluorogenic Probe for <i>In Situ</i> Labeling of Granzyme B Activity in Host Immune Response to Bacterial Infections

Bacterial infections, particularly those caused by drug-resistant bacteria, represent a pressing global health challenge. During the interaction between pathogen infection and host defense, bacterial infections initiate the host's immune response, which involves the activation of proteases that play a critical role in antibacterial defense. Granzyme B (GzmB), a key immune-related biomarker associated with cytotoxic T lymphocytes (CTLs), plays a pivotal role in this process. Therefore, detecting the activity of GzmB is crucial for understanding the host immune response to bacterial infections and for developing therapeutic strategies to overcome bacterial virulence. In this study, we designed and synthesized three granzyme B-activated near-infrared molecular probes. Among them, the probe HCy-F demonstrates in situ imaging capability, enabling precise quantification of GzmB activity. This development offers a valuable tool for monitoring immune responses and optimizing immunotherapy approaches for combating drug-resistant pathogens.