CAT and neoplasm: The Gel-HCeC-CaO2 system showed the following advantages: (i) utilized the catalase activity of HCeC to produce O2; (ii) good retention of the HCeC in the tumor; (iii) no severe systemic toxicity; (iv) alleviate tumor hypoxia environment, meeting the repeated photodynamic therapy strategy and effectively inhibiting tumor metastasis.