CD274 and neoplasm: Encapsulating PD‐L1 within biomineralized nanoparticles blocks aPD‐L1 binding to normal tissue cells during circulation, significantly enhances the accumulation of aPD‐L1 in tumor tissues via the enhanced permeability and retention (EPR) effect, and enables pH‐responsive degradation in the acidic tumor microenvironment to release aPD‐L1, restoring its activity and enhancing immunotherapy efficacy (Scheme 1C).