Granzyme B-mimetic nanozyme for nanovesicle targeted anticancer applications

Cytotoxic T lymphocytes play a crucial role in anti-tumour immunity, with granzyme B (GrB) being a decisive factor in this process. Developing a GrB-based delivery system to mimic T cell-based immunotherapy holds promise but remains challenging. Here, we present an artificial metalloenzyme (nanozyme) with GrB-like protease activity capable of inducing caspase-dependent cell apoptosis. The nanozyme is based on the site-specific binding of Pd(II) ions to recombinant human heavy chain apo-ferritin nanocages to generate a binuclear catalytic centre consisting of two Pd atoms with bridging cysteine ligands, monodentate methionine and histidine residues, and two water molecules. We show that encapsulation of the Pd-ferritin complex within membrane-fused lipid nanoparticles comprising surface-displayed single-chain antibodies affords GrB-mimicking nanozyme-based nanovesicles capable of receptor-mediated delivery of the nanozyme into the cytoplasm of tumour cells and induction of caspase-dependent apoptosis. This study provides valuable insights into the construction of nano-delivery systems with artificial GrB activity and presents a promising therapeutic option for solid tumours.