Gene delivery using dendrimer-entrapped gold nanoparticles as nonviral vectors

Development of highly efficient nonviral gene delivery vectors still remains a great challenge. In this study, we report a new gene delivery vector based on dendrimer-entrapped gold nanoparticles (Au DENPs) with significantly higher gene transfection efficiency than that of dendrimers without AuNPs entrapped. Amine-terminated generation 5 poly(amidoamine) (PAMAM) dendrimers (G5.NH(2)) were utilized as templates to synthesize AuNPs with different Au atom/dendrimer molar ratios (25:1, 50:1, 75:1, and 100:1, respectively). The formed Au DENPs were used to complex two different pDNAs encoding luciferase (Luc) and enhanced green fluorescent protein (EGFP), respectively for gene transfection studies. The Au DENPs/pDNA polyplexes with different N/P ratios and compositions of Au DENPs were characterized by gel retardation assay, light scattering, zeta potential measurements, and atomic force microscopic imaging. We show that the Au DENPs can effectively compact the pDNA, allowing for highly efficient gene transfection into the selected cell lines as demonstrated by both Luc assay and fluorescence microscopic imaging of the EGFP expression. The transfection efficiency of Au DENPs with Au atom/dendrimer molar ratio of 25:1 was at least 100 times higher than that of G5.NH(2) dendrimers without AuNPs entrapped at the N/P ratio of 2.5:1. The higher gene transfection efficiency of Au DENPs is primarily due to the fact that the entrapment of AuNPs helps preserve the 3-dimensional spherical morphology of dendrimers, allowing for more efficient interaction between dendrimers and DNA. With the less cytotoxicity than that of G5.NH(2) dendrimers demonstrated by thiazoyl blue tetrazolium bromide assay and higher gene transfection efficiency, it is expected that Au DENPs may be used as a new gene delivery vector for highly efficient transfection of different genes for various biomedical applications.