PEGylated MoS₂ quantum dots for traceable and pH-responsive chemotherapeutic drug delivery

Since low pH value is widely observed in most of solid tumors, pH-responsive drug delivery system (DDS) can provide a general strategy for tumor-targeting therapy. In this work, a traceable and pH-responsive DDS (MoS₂-PEG-DOX) based on MoS₂ quantum dots (MoS₂ QDs) is successfully developed by covalently grafting MoS₂ QDs with diamine-terminated oligomeric polyethylene glycol (PEG) and then loading with a fluorescent antineoplastic anthracycline drug, doxorubicin (DOX). The functionalization of MoS₂ QDs with PEG imparts the nanocomposite with strong blue photoluminescence, low cytotoxicity, and excellent physiological stability. The MoS₂-PEG-DOX nano-assembly can be effectively taken up by U251 cells, and an accelerated DOX release is then triggered by intracellular acid condition, which in turn diminishing unwanted side effects derived by the incorporation of DOX into healthy cells. Meanwhile, the cellular uptake of the MoS₂-PEG-DOX nano-assembly, consequent DOX release and the localization of nanocarrier can be real-time monitored due to the inherent stable fluorescence of MoS₂-PEG and DOX. These findings demonstrate that MoS₂-PEG-DOX will be promising for high treatment efficacy with minimal side effects in future therapy.