Self‐Assembly of Drug–Drug Conjugates as Drug Self‐Delivery System for Tumor‐Specific pH‐Triggered Release

An acid‐labile doxorubicin dimer (D‐DOX) is designed as drug–drug conjugate for tumor intracellular pH‐triggered release, by conjugating doxorubicin (DOX) with adipic acid dihydrazide (ADH). The dimer‐based surfactants modified with polyethylene glycol (PEG), DOX‐ADH‐DOX‐PEG or are synthesized by mono‐PEGylation and bi‐PEGylation, respectively. Then the prodrug nanoparticles are fabricated with different drug contents via dialyzing the mixture solution of D‐DOX and the PEGylated surfactants in dimethyl sulfoxide (DMSO) with different mass ratios against water. It is found that the smaller prodrug nanoparticles (142–163 nm) could be obtained with the mono‐PEGylated surfactant, than those of 157–225 nm with the bi‐PEGylated surfactant. Furthermore, the mono‐PEGylated surfactant results in a higher drug content of 51% due to their lower PEG contents. All prodrug nanoparticles could release DOX completely within 36 h at pH 5.0, with the premature drug leakage of less than 10% at pH 7.4. The 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide (MTT) assays demonstrate the proposed drug self‐delivery system possessed an enhanced anticancer efficacy against HepG2 cells than the free DOX.