Design and In Vivo Evaluation of Breast CancerTargeted pH-Responsive DOX/PEG Nanoliposomes

Abstract

 The systemic administration of doxorubicin (DOX) in the treatment of breast cancer is frequently compromised by dose-limiting cardiotoxicity and insufficient accumulation within the tumor microenvironment. To address these limitations, this study details the design, synthesis, and comprehensive in vivo evaluation of a novel pHresponsive polyethylene glycol (PEG)-modified nanoliposome system for the targeted delivery of DOX. We engineered a lipid formulation incorporating a pH-sensitivehydrazone bond that remains stable at physiological pH (7.4) but undergoes rapid hydrolysis in the acidic extracellular environment of solid tumors (pH 6.5) and endosomes (pH 5.0). The nanoliposomes were prepared via the thin-film hydration method followed by ammonium sulfate gradient loading, resulting in high encapsulation efficiency and uniform particle size distribution. Physicochemical characterization confirmed a mean hydrodynamic diameter of approximately 110 nm with a negative zeta potential that shifts towards neutrality in acidic conditions to facilitate cellular uptake. In vitro release profiles demonstrated significantly accelerated drug liberation under acidic conditions compared to physiological pH. Furthermore, in vivo pharmacokinetics and biodistribution studies in tumor-bearing mice revealed that the pH-responsive nanoliposomes exhibited prolonged circulation times and enhanced tumor accumulation via the enhanced permeability and retention effect. Crucially, the therapeutic efficacy evaluation showed superior tumor growth inhibition compared to free DOX and non-responsive liposomes, with a marked reduction in systemic toxicity and cardiotoxicity. These findings suggest that the developed pH-responsive nanocarrier represents a promising strategy for improving the therapeutic index of anthracyclines in breast cancer therapy.