A novel strategy of transition-metal doping to engineer absorption of carbon dots for near-infrared photothermal/photodynamic therapies

It is of extreme importance to engineer the structural characteristics of carbon dots (CDs) to satisfy their practical applications in imaging and medical treatments. Here, Cu,N-doped CDs (Cu,N-CDs) are a new class of near-infrared-(NIR) light-induced therapeutic agents that were prepared by a one-step hydrothermal method using EDTA·2Na and CuCl2. Specifically, CuΙΙ was located in the inner of Cu,N-CDs via N-Cu-N complexation, endowing NIR absorption for the production of heat and reactive oxygen species. The relationships between the hydrothermal temperature, NIR absorption, and intrinsic biological activity of the Cu,N-CDs were examined. The hydrothermal temperature significantly affected the latter two when the Cu content in the Cu,N-CDs was changed. The Cu,N-CDs at 180 °C were examined for cancer phototherapeutics in vitro and in vivo. The Cu,N-CDs markedly inhibited cancer via synergistic photothermal/photodynamic therapies. In addition, the Cu,N-CDs could also act as one kind of fluorescence cell-imaging agent and IR thermal imaging agent to visualize the in vitro and in vivo treatment process, respectively. Thus, the present study provides a promising new method to prepare CDs with NIR absorption feature for multifunctional cancer theranostic applications.