pH ‐Sensitive Cationic Liposomes for Oridonin and siRNA Co‐Delivery to Inhibit Triple‐Negative Breast Cancer

ABSTRACT To investigate the therapeutic efficacy of co‐delivering a small molecule compound and an interfering RNA in triple‐negative breast cancer (TNBC), a disease characterized by poor prognosis, this study developed pH‐sensitive nanocomposite cationic liposomes for the simultaneous delivery of oridonin and siCX26. CX26 (Connexin 26), a gap junction protein associated with stem‐like properties and chemoresistance, was targeted to enhance therapeutic efficacy against this aggressive subtype. Oridonin liposomes were prepared using thin‐film dispersion followed by hydrated ultrasonication. Subsequently, siCX26 was incorporated and modified with carboxymethyl chitosan (CMCS) to produce pH‐sensitive nanocomposite cationic liposomes (CMCS‐Ori‐siCX26‐LipoPH + ). Liposome stability was assessed via particle size analysis and zeta‐potential measurement. TUNEL staining and western blotting were performed to evaluate apoptosis and related intracellular signaling. The effect of CMCS‐Ori‐siCX26‐LipoPH + on tumor apoptosis was further assessed in animal models. CMCS‐Ori‐siCX26‐LipoPH + preserved siRNA integrity for up to 8 h and maintained stable particle size for up to 12 days. TUNEL staining and western blotting showed that the liposomes significantly enhanced apoptosis in MDA‐MB‐231 breast cancer cells at extracellular pH 6.5. Moreover, the liposomes delivered siRNA into the cytoplasm while protecting it from lysosomal degradation. Animal studies confirmed that CMCS‐Ori‐siCX26‐LipoPH + inhibited tumor growth and induced tumor cell apoptosis in nude mice. The CMCS‐Ori‐siCX26‐LipoPH + liposome system effectively delivers oridonin to TNBC, inducing tumor cell apoptosis.