pH/GSH Dual-Responsive Copolyprodrug for Tumor-Specific Chemo/Ferroptosis Combination Therapy

The efficacy of conventional chemotherapy is often limited by tumor heterogeneity, multidrug resistance, and off-target toxicity. Via a nonapoptotic, iron-dependent cell death mechanism, ferroptosis has emerged as a promising complement to chemotherapy. To achieve tumor-selective and synergistic treatment, pH/GSH dual-responsive amphiphilic copolyprodrug P(DOXss-Fc)-PEG was designed with high drug content (63.9% for DOX and 17.2% for FcDH), by polycondensation of disulfide-linked doxorubicin dimer (DOXss) and ferrocene dicarbohydrazide (FcDH), with DOX-PEG₂₀₀₀ as end-capping group. The self-assembled P(DOXss-Fc)-PEG-NP nanoparticles exhibited uniform spherical morphology around 95 nm, favorable stability, and minimal premature drug leakage under normal physiological condition, while efficient intracellular release of DOX, accompanied by GSH depletion and Fc-mediated Fenton reactions to enhance ferroptosis in the acidic and high-GSH tumor-like conditions. In vitro assays demonstrated efficient internalization by HepG2 cells, nuclear accumulation of DOX, and markedly reduced cytotoxicity toward normal L02 cells. Compared with free DOX, the nanoparticles exhibited enhanced antitumor activity with a lower IC₅₀ (9.11 vs 10.61 μg/mL) and a combination index (CI) of 0.95, indicating a synergistic therapeutic effect.