LAUSR

ABSTRACT In this study, we developed a peptide‐dendrimer‐drug conjugate system for the pH‐triggered direct cytosolic delivery of the cancer chemotherapeutic doxorubicin (DOX) using the pH Low Insertion Peptide (pHLIP). We synthesized a pHLIP‐dendrimer‐DOX conjugate in which a single copy of pHLIP displayed a generation three dendrimer bearing multiple copies of DOX via disulfide linkages. Biophysical analysis showed that both the dendrimer and a single DOX conjugate inserted into membrane bilayers in a pH‐dependent manner. Time‐resolved confocal microscopy indicate the single DOX conjugate may undergo a faster rate of membrane translocation, due to greater nuclear localization of DOX at 24h and 48h post delivery. At 72h, however, the levels of DOX nuclear accumulation for both constructs were identical. Cytotoxicity assays revealed that both constructs mediated ˜80% inhibition of cellular proliferation at 10&mgr;M, the dendrimer complex exhibited a 17% greater cytotoxic effect at lower concentrations and greater than three‐fold improvement in IC50 over free DOX. Our findings show proof of concept that the dendrimeric display of DOX on the pHLIP carrier (1) facilitates the pH‐dependent and temporally‐controlled release of DOX to the cytosol, (2) eliminates the endosomal sequestration of the drug cargo, and (3) augments DOX cytotoxicity relative to the free drug.