The Synthesis And Evaluation Of Stearic Acid Grafted PEI Nanoparticles As Non-viral Gene Vectors In Vitro

Objective:Gene therapy which is a new treatment method has a good application prospect. It has therapeutic potential on genetic disease, cancer and so on. It is a key step to efficiently and safely deliver gene into target cells. At present gene vectors are divided into viral and non-viral gene vector. PEI as a non-viral gene vector has been widely researched. PEI has high transfection efficiency, but it has cytotoxicity. Our study is going to synthetize a new compound PEI-SA to reduce the cytotoxicity of PEI and value the ability of PEI-SA to transport plasmid DNA and siRNA. We hoped that the modified PEI could be used as a new non-viral gene delivery vector for future gene therapy. Methods:Stearic acid (SA) was grafted onto PEI through amidation. The structure of PEI-SA was characterized by FTIR and1H NMR analyses. The size and morphology of polyplexes were observed using transmission electron microscopy (TEM). Size and zeta potential was measured by dynamic light scattering (DLS). The ability of PEI-SA to bind and protect nucleic acids was tested by gel retardation assays. Cytotoxicity of PEI-SA was tested by MTT assays. Transfection results were observed by fluorescence microscopy and flow cytometry. Results:In the FTIR results of PEI-SA we found the peaks which were attributed to the N-H of amido bond bending vibration and C-N of amido bond stretching vibration. In1H NMR spectra results the characteristic peaks of SA and PEI could be seen in the result of PEI-SA. These results indicated that SA was successfully grafted on PEI. The size and zeta potential of PEI-SA was61.2±22.4nm and25.5±4.5mV. When PEI-SA combined nucleic acid molecules, its size and zeta potential was70.9±41.4nm and18.0±4.5mV. PEI-SA exhibited good ability to condense pDNA into compact and spherical nanoparticles. PEI-SA could protect pDNA from degradation by DNase I. When the concentration of PEI-SA was lower than32μg/mL, PEI-SA had no cytotoxicity. However when the concentration of PEI was higher than8μg/mL its cell viability was lower than60%. When the weight ratio between PEI-SA and pDNA was8, the transfection efficiency of PEI-SA was5.1±0.2%; when the weight ratio between PEI-SA and small interfering RNA (siRNA) was32, the transfection efficiency of PEI-SA was93.5%. Conclusion:The SA grafted PEI has lower cytotoxicity than PEI. PEI-SA can be used as an effective non-viral gene delivery vector.