CAT and neoplasm: The proposed Ti3C2-MnO2-PDA was acid-responsive since PDA could slowly disintegrate in acidic conditions at tumor sites and expose MnO2, meanwhile, this nanocomposite exhibited peroxidase-like activity and catalase-like activity which can catalyze the production of toxic ∙OH radicals from H2O2 to enable the catalytic therapy with local oxygen supply (Lin et al., 2018b; Ma et al., 2021).