IL2 and neoplasm: Upon intravenous injection, Doxy@CaCO3-PEG enabled the spatially selective activation of tumor-infiltrating Tet-HER1-CAR-T cells without causing any obvious secretion of pro-inflammatory cytokines (e.g. interleukin 2 (IL-2), interferon-γ (IFN-γ) and tumor necrosis factor-α (TNF-α)) into the blood compared with that in mice treated with free Doxy-activated Tet-HER1-CAR-T cells and conventional HER1-CAR-T cells.