As there are cell-suicide weapons existing in mitochondria, the mitochondria-mediated apoptosis pathway is an effective option for cancer therapy. However, the efficacy of this kind of chemotherapy are greatly reduced due to the apoptosis evading of cancer cells allowed by the anti-apoptotic proteins that are over-expressed in the mitochondria of many malignant tumors, such as Bcl-2 protein.
In order to deliver siRNA and chemotherapeutic agents to tumor cells and mitochondria sequentially, a hierarchy targeted delivery system has been constructed. By the conjugation to the polyethyleneimine in chitosan-graft-PEI (CP) and the complexation with siRNA, the copolymer TPP-CP-LND (TCPL) was synthesized by the mitochondria-targeting ligand triphenylphosphine (TPP) and therapeutic drug lonidamine (LND). The complexes were coated with poly(acrylic acid)-polyethylene glycol-folic acid (PPF) copolymer to form a hierarchical targeted co-delivery system (TCPL/siRNA/PPF NPs) that had a neutral surface charge, exhibited pH-sensitve shell separation and were stable in plasma. After FA-directed internalization, the TCPL/siRNA/PPF NPs simultaneously released siBcl-2 into the cytoplasm, delivered LDN to mitochondria in the same cancer cell, and activated mitochondria apoptosis pathway. The mitochondria apoptosis pathway for cancer therapy can be stimulated by RNA-interference and mitochondria-targeted chemotherapeutics.