CRGD grafted liposomes containing inorganic nano-precipitate complexed siRNA for intracellular delivery in cancer cells

Abstract

Development of effective vector for intracellular delivery of siRNA has always been a challenge due to its hydrophilicity, net negative surface charge and sensitivity against nucleases in biological milieu. The present investigation was aimed to develop a novel non-viral liposomal carrier for siRNA delivery. Nano-precipitate of calcium phosphate was entrapped in liposomes composed of a neutral lipid (DPPC), a fusogenic lipid (DOPE), a PEGylated lipid (DSPE-mPEG2000) and cholesterol. siRNA was made permeable through liposomal bilayer and complexed to calcium phosphate precipitates inside the liposomes. siRNA entrapped liposomes were further grafted with cRGD to achieve targeting potential against cancer cells. More than 80% of siRNA was entrapped inside the liposomes having average particle size below 150nm. Cryo-transmission electron microscopy revealed the intra-liposomal calcium phosphate precipitation and unilamellar morphology of prepared liposomes. The viability of A549 lung cancer cells was significantly higher after treatment with siRNA entrapped liposomes as compared to Lipofectamine2000 complexed siRNA. Fluorescent intensity in lung carcinoma cells was significantly higher after exposure to fluorescent siRNA entrapped liposomes than with Lipofectamine2000, which were confirmed by both confocal microscopy and flow cytometry. Live imaging by confocal microscopy ascertained the targeting efficacy of cRGD grafted liposomes compared to naked siRNA and non-grafted liposomes. Developed liposomal formulation showed effective protection of siRNA against serum nucleases along with less haemolytic potential and excellent stability against electrolyte induced flocculation. At 5nM concentration gene expression of target protein was reduced up to 24.1±3.4% while Lipofectamine2000 reduced expression level up to 26.35±1.55%. In vivo toxicity in mice suggested admirable safety profile for developed lipid based delivery vector. These results advocate that prepared liposomal system would be of high value for intracellular delivery of siRNA.