Biotin and TAT dual-stage targeting polymersomes for improved nuclear delivery of doxorubicin

A dual-stage targeting Pluronic F127/polylactic acid (PLA) polymersome modified with biotin (cell surface targeting) and trans-activator of transcription (TAT, cell nucleus targeting) [Biotin(TAT)-F127-PLA] was prepared by the biotin-avidin bridging technology to inhibit multidrug resistance (MDR) of cancer cells. Hydrophilic doxorubicin (DOX) was loaded into the polymersome to obtain Biotin(TAT)-F127-PLA/DOX with a size of 127.4 ± 1.7 nm. Its loading efficiency and loading capacity were 23.3% and 8.8%. The cytotoxicity of Biotin(TAT)-F127-PLA/DOX with different molar ratios of Biotin to TAT against doxorubicin-resistant A549/ADR and A549 human non-small-cell lung cancer cells followed the order: 10%:10% > 10%:5% > 10%:20% > 10%:30%. Biotin(TAT)-F127-PLA/DOX showed stronger cytotoxicity, better cellular and nuclear uptake than single-ligand and nontargeted polymersomes. Notably, even though the cellular uptake of TAT-F127-PLA/DOX was 0.95 times that of Biotin-F127-PLA/DOX, it achieved 1.02-fold nuclear uptake compared with Biotin-F127-PLA/DOX, demonstrating the nuclear-localization ability of TAT ligands. The uptake of Biotin(TAT)-F127-PLA/DOX by A549/ADR cells was proved to be related to the endocytosis mediated by biotin receptor. In addition, MDR mechanism study showed that the ability of Biotin(TAT)-F127-PLA/DOX to reduce adenosine-triphosphate (ATP) content and increase reactive oxygen species (ROS) levels in A549/ADR cells was better than other DOX-loaded polymersomes. More importantly, the tumor volume relative to the start point of 4T1 tumor-bearing mice intraperitoneally injected with Biotin(TAT)-F127-PLA/DOX polymersomes was only 451.06% at day 15 at an ultralow DOX dose (0.2 mg/kg), which was 25.09% of that treated with free DOX, indicating the superior tumor growth inhibition of the dual-stage targeting polymersome.