Acid-sensitive PEG-removable nanoscale liposomes for delivery of doxorubicin in A549/ADR therapy

Abstract

Polyethylene glycol (PEG), which can impart long cycling performance to drug carriers, has been commonly used for drug carrier modification. However, PEG modification impedes cellular uptake of drug carriers and intracellular release of drugs, a problem known as the “PEG dilemma” that limits its application. In this study, we designed and synthesized mPEG-NCH-DOB molecules with acid-sensitive hydrazone bonding for the responsive removal of PEG. Drug-loaded lipid PHDGX for doxorubicin (DOX) delivery was obtained by compounding mPEG-NCH-DOB with lipid DOPG, which possess the capability for long cycling, and acid-sensitive PEG-removal to accelerate drug release and enhance cellular uptake. mPEG-NCH-DOB could reach 50% fracture rate after 24 h at pH 5.0. The cytotoxicity assay and flow cytometry (FCM) results showed that PHDGX could enter A549/ADR cells more easily than free DOX at low DOX concentrations and has stronger anti-cancer ability. Through a confocal laser-scanning microscopy (CLSM) study, PHDGX was found to enter the nucleus of A549/ADR cells more easily than free DOX at the same time point, which indicated that PHDGX could overcome the DOX resistance of A549/ADR at low DOX concentrations. The 3D tumor microsphere (MC) growth inhibition assay showed that PHDGX not only has the best MC inhibition ability but also has better MC penetration ability than free DOX. Therefore, this drug-loaded liposome has good stability under conventional conditions and responsive PEG removal in the tumor acid environment, offering a potential strategy for utilizing PEG in drug carrier modification and overcoming tumor resistance to free drugs.