The effect of linkers on the self-assembling and anti-tumor efficacy of disulfide-linked doxorubicin drug-drug conjugate nanoparticles

Drug-drug conjugate nanoparticles (DDC NPs) is a potential method for overcoming poor solubility and nonspecific action in cancer therapy, which is based on its high drug loading efficiency and passive tumor-target properties. Our laboratory has prepared DOX-SS-DOX NPs based on disulfide-linked doxorubicin (DOX) drug-drug conjugate, which showed well physical stability and similar anti-tumor efficacy as liposomes. However, how structures of DDCs influence the self-assembling and anti-tumor efficacy is still seldom clarified and needs further investigation. Here, we discussed the role of linker types, length and linkage site in the NPs self-assembling and anti-tumor efficacy. A series of DOX prodrugs were prepared and all the prodrugs could selfassemble into NPs except DOX-SS-DOX (2), indicating the linker length played an important role during selfassembling process. The linkage sites and types of linker exhibited great influence on in vitro cytotoxicity and in vivo anti-tumor efficacy, particularly, modification on C-14 hydroxyl was more efficient for DOX release than on amino group. Besides, disulfide-bond was not cleaved and DOX-SH release did not occur in the metabolism process. The function of disulfide-bond was to enhance the release of DOX in the hydrolysis process. These findings is meaningful for effective prodrug NPs design for therapeutics.