Selectively Fluorinated PAMAM-Arginine Conjugates as Gene Delivery Vectors

Polyamidoamine (PAMAM)dendrimers are among the most studied cationicpolymers as non-viral gene delivery vectors. However, an idealPAMAM-based gene delivery vector is still missing due to the highmanufacturing costs and non-negligible cytotoxicity associated withthe use of high-generation dendrimers, whereas low-generation dendrimersare far from displaying efficient gene transfection. In order to coverthis gap in the literature, in this study, we propose the functionalizationof the outer primary amines of PAMAM G2 and PAMAM G4 with buildingblocks bearing fluorinated moieties along with a guanidino functionalgroup. We have designed and synthetized two fluorinated arginine (Arg)-basedMichael acceptors which were straightforwardly clickedto PAMAM dendrimers without the need for coupling reagents and/orcatalysts. The obtained conjugates, in particular, derivative 1 formed starting from the low-cost PAMAM G2 and a buildingblock bearing two trifluoromethyl groups, were able to efficientlycomplex plasmid DNA, had negligible cytotoxicity, and showed improvedgene transfection efficiency as compared to undecorated PAMAM dendrimersand a corresponding unfluorinated PAMAM-Arg derivative, withderivative 1 being two orders of magnitude more efficientthan the gold standard branched polyethylenimine, bPEI, 25 kDa. Theseresults highlight the importance of the presence of trifluoromethylmoieties for both gene transfection and a possible future applicationin F-19 magnetic resonance imaging.

Automated summary

In this study, we successfully functionalized PAMAM G2 and PAMAM G4 with fluorinated arginine-based building blocks, resulting in a novel PAMAM-based gene delivery vector. The conjugates showed improved binding capacity to plasmid DNA, reduced cytotoxicity, and enhanced gene transfection efficiency compared to undecorated PAMAM dendrimers. These findings are of great importance for gene delivery research and also have the potential for future application in F-19 magnetic resonance imaging.