Dual stimuli-responsive nanocarriers based on polyethylene glycol-mediated schiff base interactions for overcoming tumour chemoresistance.

Multifunctional and stimulus-sensitive intelligent nanodrug delivery systems (NDDSs) can significantly optimize the effectiveness of theranostic agents for cancer treatment. In this study, redox and pH dual-responsive nanocarriers (CPNPs) were prepared through molecular assembly by utilizing the Schiff base interactions of cystamine (Cys), PEG-NH2 and formaldehyde (FA) under aqueous conditions with a one-pot, one-step technique. First, the degradation products of CPNPs exhibited good biocompatibility, and the high concentration of intact CPNPs (200 µg/mL) could inhibit the growth of cells. In addition, doxorubicin (DOX) was encapsulated in CPNPs simply by changing the pH (DOX@CPNPs), and pH/GSH-responsive release behaviour was confirmed. In vitro, CPNPs significantly increased the uptake of DOX and enhanced the cytotoxicity of DOX to tumour cells. More importantly, DOX@CPNPs strongly reversed drug resistance in three different types of cancer cells, exhibiting significant anticancer effects. Collectively, this study presents the easy preparation of nanomedicines that respond to multiple stimuli, which highlights the advantages of Schiff base-based nanomedicines for cancer therapy and reversing chemoresistance.