Polyethyleneimine-Coated Gold Nanoparticles: Straightforward Preparation of Efficient DNA Delivery Nanocarriers

A novel one-pot method for the synthesis of polyethyleneimine (PEI)-coated gold nanoparticles (AuPEI-NPs) that combines the reductant-stabilizer properties of PEI with microwave irradiation starting from hydrogen tetrachloroaurate acid (HAuCl₄ ) and branched PEI 25 kDa (b25kPEI) was explored. The method was straightforward, green, and low costing, for which the Au/PEI ratio (1:1 to 1:128 w/w) was a key parameter to modulate their capabilities as DNA delivery nanocarriers. Transfection assays in CHO-k1 cells demonstrated that AuPEI-NPs with 1:16 and 1:32 w/w ratios behaved as effective DNA gene vectors with improved transfection efficiencies (twofold) and significantly lower toxicity than unmodified b25kPEI and Lipofectamine 2000. The transfection mediated by these AuPEI-NP-DNA polyplexes preferentially used the caveolae-mediated route for intracellular internalization, as shown by studies performed by using specific internalization inhibitors as well as colocalization with markers of clathrin- and caveolae-dependent pathways. The AuPEI-NP polyplexes preferentially used the more efficient caveolae internalization pathway to promote transfection, a fact that supports their higher transfection efficiency relative to that of Lipofectamine 2000. In addition, intracellular trafficking of the AuPEI-NPs was studied by transmission electron microscopy.