Objective      To prepare polyethyleneimine (PEI) capped Au nanoparticles for gene vector and investigate their physicochemical prosperities and transfection efficiency in vitro.       Methods      PEI-capped Au nanoparticles acting as gene carrier were prepared by using PEI as the reductant of hydrogen tetrachloroaurate (HAuCl4). pAcGFP-N1 DNA was used as reporter gene bind to Au nanoparticles by electrostatic adsorption. The appearance and morphology of nanoparticles were characterized by ultraviolet spectrophotometry and transmission electron microscopy (TEM)

respectively. The grain distribution and zeta potentials of the nanoparticles were determined with laser grain analyzer. DNA binding capacity of PEI capped Au nanoparticles was detected by agarose gel electrophoresis. The cytotoxicity of PEI-capped Au nanoparticles to HEK293 cells was examined by CCK-8 assay. The transfection activities of PEI-capped Au nanoparticles was assessed by in vitro gene transfection. The transfection of the vector pAcGFP-N1 to HEK293 cells was observed by fluorescence microscopy and the efficiency was determined.       Results      Our prepared PEI capped nanoparticles were distributed dispersely

in spherical shape of 12.3±3.3 nm in diameter

with zeta potential of 29.7±5.1 mV under the pH value of 7.2

and could obtain positively charged nanoparticles. Agarose gel electrophoresis indicated that when the weight ratio of AuNP to DNA≥0.5

DNA could bind to the Au nanoparticles completely. In vitro transfection showed that the DNA-PEI nanoparticles could be transfected into HEK293 cells

and the gene could be expressed in the cells with a transfection efficiency of 25%.       Conclusion      PEI capped Au nanoparticles is a novel non-viral gene vector

with the advantages of high transfection efficiency and low cytotoxicity.