Design and synthesis of a broccoli-based carrier and photosensitizer for chemo-photodynamic therapy of cancer.

Cancer is one of the major threats to human health. Conventional single-drug chemotherapy has limitations, including low drug utilization, severe side effects, poor efficacy, and high recurrence risk. Combination therapies have proven effective for antitumor treatment. In this study, biomass carbon dots (CDs) were synthesized via one-step hydrothermal carbonization using broccoli as the only precursor. Double-stranded DNA containing an i-motif structure, which responds to environmental pH, was conjugated to the biomass CDs through an amide bond. The anticancer drug doxorubicin (DOX) was intercalated into the double-stranded 5'-GC-3' or 5'-CG-3' DNA duplex sequences via hydrophobic and hydrophilic interactions to form a CD-D(DOX) that may serves as a non-toxic carrier and photosensitizer. After cellular uptake, the C-rich strands in CD-D(DOX) responded to the acidic lysosomal environment, resulting in the formation of a stable C-tetrad (i-motif) structure, dehybridization of the complementary strands, and triggered drug release. Under light irradiation, the biomass CDs generated singlet oxygen and thus enabled photodynamic therapy. Upon 660 nm laser irradiation, CD-D(DOX) exhibited excellent synergistic antitumor efficacy. These findings may support the treatment of solid tumors through synergistic therapy.