Charge Conversional Biomimetic Nanosystem for Synergistic Photodynamic/Protein Therapy

Cytochrome C (Cytc) has received considerable attention due to its ability to induce tumor apoptosis and generate oxygen to improve photodynamic therapy (PDT) efficiency. However, the damage to normal tissues caused by nonspecific accumulation of Cytc limits its application. Herein, in order to reduce its toxicity to normal tissues while retaining its activity, a charge conversional biomimetic nanosystem (CA/Ce6@MSN-4T1) is proposed to improve the tumor targeting ability and realize controlled release of Cytc in the tumor microenvironment. This nanosystem is constructed by coating tumor cell membrane on mesoporous silica nanoparticles coloaded with a photosensitizer (chlorin e6, Ce6) and the citraconic anhydride conjugated Cytc (CA) for synergistic photodynamic/protein therapy. The coating of the tumor cell membrane endows the nanoparticles with homologous targeting ability to the same cancer cells as well as immune escaping capability. CA undergoes charge conversion in the acidic environment of the tumor to achieve a controlled release of Cytc. The released Cytc can relieve cellular hypoxia to improve the PDT efficiency of Ce6 and can induce programmed cell death. Both in vitro and in vivo studies demonstrated that CA/Ce6@MSN-4T1 can efficiently inhibit the growth of tumors through synergistic photodynamic/protein therapy, and meanwhile show reduced side effects on normal tissues.