Co-Polymer Functionalised Gold Nanoparticles Show Efficient Mitochondrial Targeted Drug Delivery in Cervical Carcinoma Cells

The mitochondria have recently become a novel target in the treatment of cancer. Targeted delivery by nanoparticles (NPs) has shown potential in enhancing existing therapeutic principles. With toxicity remaining a recurring issue, the green synthesis of inorganic NPs and modification with polymers may help to improve stability and biocompatibility. We synthesized epigallocatechin gallate (EGCG)-capped gold NPs (AuNPs), and functionalized with poly-D-lysine grafted polyethylene glycol (PDL-g-PEG), and the mitochondrial targeting triphenylphosphonium cation, and thereafter assessed their mitochondrial delivery capacity of paclitaxel in cancer cells in vitro. This PDL-g-PEG coated EGCG-AuNPs were further assessed for their laminin receptor avidity and mitochondrial localisation potential, upon functionalisation with the delocalised cation, triphenylphosphine. The laminin receptor dependent uptake and mitochondrial localisation of targeted T-Au(PDL-g-PEG) NPs were confirmed by ICP-OES and fluorescent microscopy. Their delivery of paclitaxel to the mitochondria of cancer cells elicited significant cytotoxicity especially in the human cervical carcinoma (HeLa) cell line, compared to the untargeted T-Au(PDL-g-PEG) and free drugs. Mechanistic studies implicated caspase dependent apoptosis as the mechanism of cell death. Our findings demonstrate the capacity of T-Au-[PDL-PEG] NPs to preferentially localize in the tumour mitochondria, and confirms the potential impact of subcellular targeting, especially to the mitochondria in cancer cells for an improvement in the therapeutic indices of these drugs.