Synthesis and physicochemical characteristics of galactosylated poly(ethylene glycol)-graft-polyethylenimine as a hepatocyte-targeting nano-gene carriers

Background: Galactosylated poly(ethylene glycol)-graft-polyethylenimine (Gal-PEG-PEI) can be prepared as a nano-gene carrier of hepatocyte-targeting plasmid siRNA (psiRNA) through the glycosyl galactose of PEG-PEI. Objective: To synthesize Gal-PEG-PEI and study its physicochemical characteristics, so as to provide references for further study on the transfection. Design, time and setting: The controlled experiments concerning about gene engineering were accomplished in Biomedical Engineering Centre of Sun Yat-sen University from October 2007 to June 2008. Materials: The Gal-PEG-PEI was synthesized by two-step method. Methods: The physicochemical characteristics of the Gal-PEG-PEI/psiRNA nanoparticles were measured by nanoparticle-zeta electric potential instrument, transmission electron microscopy, gel retardation and ethidium bromide binding assay. Cytotoxicity of Gal-PEG-PEI was studied in cultured HepG2 cells by Cell Counting Kit-8 assay. The transfection experiments were performed with the Gal-PEG-PEI/psiRNA in HepG2 cells and the transfection efficiency was determined. Main outcome measures: The particle sizes and zeta potentials of Gal-PEG-PEI/psiRNA; Encapsulation ability; Cytotoxicity results; Transfection efficiency in HepG2 cells. Results: The particle sizes of Gal-PEG-PEI/psiRNA decreased with increasing charge ratios of Gal-PEG-PEI to psiRNA and had a minimum value of 81.1 nm, while the zeta potentials were increased accordingly. Gal-PEG-PEI had a perfect ability to encapsulate psiRNA. Cytotoxicity of Gal-PEG-PEI was lower than that of PEI and transfection efficiency of Gal-PEG-PEI was higher than that of PEI without modification in HepG2 cells. Conclusion: The Gal-PEG-PEI nano-gene carrier can be synthesized successfully, it displays perfect ability to hepatocyte-targeting and little cytotoxicity.