Transferrin Conjugated pH- and Redox-Responsive Poly(Amidoamine) Dendrimer Conjugate as an Efficient Drug Delivery Carrier for Cancer Therapy

Introduction: A multifunctional redox- and pH-responsive polymeric drug delivery system is designed and investigated for targeted anticancer drug delivery to liver cancer. Methods: The nanocarrier (His-PAMAM-ss-PEG-Tf, HP-ss-PEG-Tf) is constructed based on generation 4 polyamidoamine dendrimer (G4 PAMAM). Optimized amount of histidine (His) residues is grafted on the surface of PAMAM to obtain enhanced pH-sensitivity and proton-buffering capacity. Disulfide bonds (ss) are introduced between PAMAM and PEG to reach accelerated intracellular drug release. Transferrin (Tf) was applied to achieve active tumor targeting. Doxorubicin (DOX) is loaded in the hydrophobic cavity of the nanocarrier to exert its anti-tumor effect. Results: The results obtained from in vitro and in vivo evaluation indicate that HP-ss-PEG-Tf/DOX complex has pH and redox dual-sensitive properties, and exhibit higher cellular uptake and cytotoxicity than the other control groups. Flow cytometry and confocal microscopy display internalization of HP-ss-PEG-Tf/DOX via clathrin mediated endocytosis and effective endosomal escape in HepG2 cancer cells. Additionally, cyanine 7 labeled HP-ss-PEG-Tf conjugate could quickly accumulate in the HepG2 tumor. Remarkably, HP-ss-PEG-Tf/DOX present superior anticancer activity, enhanced apoptotic activity and lower heart and kidney toxicity in vivo. Discussion: Thus, HP-ss-PEG-Tf is proved to be a promising candidate for effective targeting delivery of DOX into the tumor.