Triphenylphosphonium-modified poly(ethylene glycol)-poly(ε-caprolactone) micelles for mitochondria- targeted gambogic acid delivery

Mitochondria are important targets for the intracellular delivery of drugs and DNA. For mitochondria-targeted delivery, a mitochondriotropic molecule, triphenylphosphonium (TPP), was applied to the synthesis of amphiphilic TPP-poly(ethylene glycol)-poly(ε-caprolactone) (TPP-PEG-PCL) polymers. The TPP-PEG-PCL polymer was used to prepare micelles using a solvent evaporation method for the delivery of gambogic acid (GA) (GA-TPP). The micelles were obtained with a favorable particle size of 150.07 ± 11.71 nm and an encapsulation efficiency of 80.78 ± 1.36%, and they displayed homogeneous spherical shapes. The GA-TPP micelles exerted enhanced cytotoxic and pro-apoptotic effect against A549 cells compared to free GA and GA-loaded PEG-PCL (GA-PP) micelles, due to the inhibition of the expression of apoptosis-related proteins and promotion of caspase 3/7 and caspase 9 activity. Notably, the mitochondria-targeting GA-TPP micelles selectively accumulated in the mitochondria, inducing the loss of mitochondrial membrane potential and the release of cytochrome c, thereby achieving improved mitochondria-targeting effects. In conclusion, the GA-TPP micelle system shows great promise for lung cancer treatment by inducing an apoptotic effect via the mitochondrial signaling pathway.