Polyethylenimine modified calcium phosphate nanoparticles for efficient siRNA delivery and K-ras gene knockdown

摘要

Introduction: As one of the important ways of gene therapy, RNA interference has attracted more and more attention. Developing a safe and efficient carrier to guide siRNA into target cytoplasm is a critical challenge in RNA interference field. Calcium phosphate nanoparticles were developed as a carrier nearly 40 years ago and it got enormous attention due to its ability to condense and release cargo efficiently. Materials and Methods: In this study, calcium phosphate nanoparticles were synthesized with the regulation of PEG and then modified by polyethylenimine (PEI). The prepared nanoparticles were mixed with siRNA and then used to transfect human pancreatic cancer cell lines. The efficiency of the delivered siRNA and its K-ras gene knockdown effect were also studied. Results and Discussion: The prepared spherical nanoparticle was confirmed to have a diameter of ＜ 50 nm with a narrow size distribution. As a natural inorganic material, the nanoparticle has little cytotoxicity on normal human pancreatic ductal epithelial cell line HPDE6-C7 and human pancreatic cancer cell lines PANC-1, BXPC-3, CFPAC-1. After 3 months' degradation in PBS solution with pH value of 5.6,6.5,7.4, the degradation percentage of nanoparticles reached 80%, 50%, 40% respectively. When the quality ratio of the nanoparticle and RNA was 8:1, the loading efficiency of RNA was almost 100%. The in vitro test indicated that luciferase FAM-siRNA delivered by the nanoparticle could enter PANC-1 and CFPAC-1 cells successfully, and the transfection efficiency is higher than the conventional siRNA-MateTM. Real-time fluorescent quantitative PCR and western blotting results demonstrated that the siRNA loaded by nanoparticle could silence k-ras gene in RNA and protein expression levels. Meanwhile, knockdown k-ras by transfection complex could significantly induce the apoptosis of PANC-1 cells in vitro. Conclusion: Cytotoxicity studies demonstrated that the prepared nanoparticles have excellent biocompatibility which is most important to be used as an siRNA carrier. Degradation experiment showed the good biodegradation ability of the synthesized nanoparticles. Transfection and silence experiments proved that the carrier can be applied to knockdown k-ras gene and promote the apoptosis of tumor cells successfully. All the results illustrated the prepared nanoparticles could be used as a safe and effective siRNA delivery system for anticancer therapy.