Carboxymethyl chitosan-based nanoparticles of acid response for the synergistic anti-tumor effect of PDT and chemotherapy

The combination of multiple anti-tumor methods has shown significant application potential in overcoming the limitations of monotherapy. Photodynamic therapy (PDT) and chemotherapy combination is a promising strategy for reducing drug resistance and side effects. Here, inspired by the acidic environment of tumors, carboxymethyl chitosan-based pH-responsive nanovesicles were developed to co-deliver the chemotherapeutic drug doxorubicin (DOX) and photosensitizer 5-aminolevulinic acid (5-ALA). The in vitro drug release studies revealed that drugs could be responsively released when nanoparticles were triggered by the acidic environment. The controlled-release behavior improved drug retention and reduced the administration time. Our nanoparticles could significantly enhance the killing effect of drugs on tumor cells and increase intracellular levels of reactive oxygen species (ROS) compared to monotherapy, effectively achieving the effects of combined chemotherapy and PDT. The loaded DOX could kill tumor cells and the loaded 5-ALA could enhance the content of protoporphyrin IX (PpIX), resulting in excess ROS production to improve the effects of PDT. In summary, our nanoparticles could co-deliver the drugs and exert synergistical anti-tumor of PDT and chemotherapy by suppressing tumor cell proliferation and facilitating cell apoptosis.