Doxorubicin-loaded environmentally friendly carbon dots as a novel drug delivery system for nucleus targeted cancer therapy

Chemotherapy is widely applied against various kinds of carcinoma. Generally, chemotherapeutic agents, such as Doxorubicin (DOX), Paclitaxel (PTX), 5-Fluorouracil (5-FU), Methotrexate (MTX), and Vinblastine (VLB) are combined with a view to maximizing their efficacy. Unfortunately, chemotherapeutics are indiscriminate and also kill normal healthy cells, resulting in serious side effects. This non-productive and destructive distribution of chemotherapeutics is regarded as one of the largest problems associated with chemotherapy. Recently, the application of carbon dots (CDs) in cancer therapy has attracted considerable attention due to their attractive properties, such as biocompatibility and low toxicity. We report herein on the fabrication of CD-DOX antitumor drug complexes, from the combination of CDs and DOX, with a view to providing a novel and efficient strategy for cancer treatment. CDs were synthesized by hydrothermal treatment of milk, a simple and environmentally friendly synthetic process. DOX was conjugated to the CDs through electrostatic interactions via the multiple surface CD functional groups. The CD-DOX complexes exhibited pH-dependent DOX release behavior. A cytotoxicity study demonstrated that the CDs were non-cytotoxic in the range of concentrations used. Compared to free DOX, the CD-DOX complexes were significantly more destructive to the adenoid cystic carcinoma cell line (ACC-2), but exhibited lower toxicity to a mouse fibroblast cell line (L929). Confocal microscopy and flow cytometry confirmed that CD-DOX complexes increased cancer therapy efficiency through the localization of a much higher quantity of drugs in the nuclei of tumor cells and induced a higher rate of apoptosis in ACC-2 cells, compared to DOX alone.