Redox and pH dual sensitive carboxymethyl chitosan functionalized polydopamine nanoparticles loaded with doxorubicin for tumor chemo-photothermal therapy.

The high expression of reduced glutathione (GSH) and low pH in tumor sites have encouraged new ideas for targeted drug release. The tumor microenvironment is a crucial target for studying the anti-tumor efficiency of photothermal therapy because the microenvironment plays a key role in cancer progression, local resistance, immune escaping, and metastasis. Herein, active mesoporous polydopamine nanoparticles loaded with doxorubicin and functionalized with N,N'-bis(acryloyl)cystamine (BAC) and cross-linked carboxymethyl chitosan (CMC) were used to induce simultaneous redox- and pH-sensitive activity to achieve photothermal enhanced synergistic chemotherapy. The inherent disulfide bonds of BAC were able to deplete glutathione, thus increasing the oxidative stress in tumor cells and enhancing the release of doxorubicin. Additionally, the imine bonds between CMC and BAC were stimulated and decomposed in the acidic tumor microenvironment, improving the efficiency of light conversion through exposure to polydopamine. Moreover, in vitro and in vivo investigations demonstrated that this nanocomposite exhibited improved selective doxorubicin release in conditions mimicking the tumor microenvironment and low toxicity towards non-cancerous tissues, suggesting there is high potential for the clinical translation of this synergistic chemo-photothermal therapeutic agent.