Cationic amphiphilic calixarenes to compact DNA into small nanoparticles for gene delivery

Macrocycles have been attracting increasing attention as scaffolds for preparation of non-viral vectors for gene delivery. Here, following our earlier report, a series of amphiphilic calixarenes bearing cationic choline or N-(2-aminoethyl)-N,N-dimethylammonium groups at the upper rim and alkyl chains at the lower rim were synthesized. The effect of the length of aliphatic chains and the structure of the head group on their self-assembly, interaction with DNA, properties of their DNA complexes, transfection efficiency and cytotoxicity was studied. It was found that longer alkyl chains favor formation of small virus-sized DNA nanoparticles with low polydispersity. Moreover, longer alkyl chains, such as dodecyl groups, significantly improved the transfection efficiency, so transfection was observed in the presence of fetal bovine serum as well as with or without a helper lipid. Finally, we observed that the cytotoxicity of these calixarenes clearly decreased with increase of the chain length. On the other hand, the presence of four additional amino groups, which could be protonated at pH < 7, affected only the stoichiometry of the complexes with DNA without influencing their transfection efficiency or cytotoxicity. The results obtained provide new insights for designing non-viral vectors based on macrocyclic molecules.