Construction of mannose-grafting Fe-doped carbon dots for CpG delivery and photothermal ablation of tumor

Photothermal therapy (PTT) can kill the tumor in situ, but fail to trigger strong antitumor immune response against its recurrence and metastasis. Herein, mannose-grafting Fe-doped carbon dots (M/Fe-CDs) were prepared via hydrothermal carbonization and chemical modification. The prepared M/Fe-CDs had characteristics of excellent optical qualities, good water solubility, and outstanding biocompatibility. Compared with pure CDs, the doping of Fe atom endowed the M/Fe-CDs with a high photothermal conversion efficiency (from 12.1 up to 30.1%). Under 808-nm NIR irradiation, the M/Fe-CDs could lead to local hyperthermia to kill tumor cells. Importantly, the M/Fe-CDs were capable of loading CpG-ODNs via electrostatic absorption and delivering them into the cytoplasm of dendritic cells (DCs). Finally, the CpG-ODNs-loading M/Fe-CDs could significantly increase the CD80/86 expression on the DCs surface. These results demonstrated that the M/Fe-CDs could be used as a versatile nanoplatform to combine the PTT and immune activation for tumor treatment.