Tunable multi-responsive N-heterocyclic carbene-gold nanoenzyme for tumor-specific pyroptosis and immune activation in cancer therapy

Heterogeneity of the tumor microenvironment (TME) poses significant obstacles to effective tumor treatment. Pyroptosis-based immunogenic cell death (ICD) therapy is an ideal strategy to overcome TME heterogeneity and achieve a satisfactory antitumor effect. However, specific activation of pyroptosis in tumors while sparing normal tissue still remains a great challenge. Here, we have developed novel, biocompatible N-heterocyclic carbenes-gold nanoparticles (NHC@AuNPs) as TME-responsive nanoenzyme and potential pyroptosis inducers through an azide-alkyne cycloaddition “click” reaction and direct aurophilic interaction (Au^I∙∙∙Au^I). The NHC@AuNPs demonstrated tunable multi-responsive abilities within the TME, including superior peroxidase (POD) activity, GSH depletion through on-site cleavage Au-Au bond, inhibition of thioredoxin reductase and enhancement of ROS. This ROS buildup damages mitochondria, further enhancing H₂O₂ release and amplifying the catalytic cycle of ROS production. NHC ligation also exhibited enhanced fusion of NPs with the lipid bilayer, promoting high intracellular uptake in cancer cells. In vitro and in vivo experiments demonstrated that NHC@AuNPs effectively trigger pyroptosis in tumor cells through the ROS-modulated NLRP3/caspase-1/GSDMD pathway and activate antitumor immunity, such as the increased infiltration of CD4⁺ and CD8⁺ T cells, as well as the significant release of proinflammatory cytokines. These findings provide valuable insights for designing pyroptosis-inducer in cancer therapies.