Supramolecular protection-mediated one-pot synthesis of cationic gold nanoparticles

Despite the extended use of cationic gold nanoparticles (AuNPs) in biomedical applications, direct one-pot synthesis of AuNPs with tunable size in aqueous media is limited due to the deleterious electrostatic attraction between AuCl4-anions and positively charged ligands. This paper describes the one-pot synthesis of cationic gold nanoparticles with size tunability based on host-guest chemistry. As the host molecule, cucurbit[7]uril inhibits self-aggregation in aqueous solution by threading positively charged guest ligands, which provides a shielding effect on the ligands. Reduction of the mixtures by directly adding NaBH4 generates cationic AuNPs with narrow size distributions. Furthermore, their potential in biomedical applications is demonstrated by siRNA transfection experiments. This approach relying on supramolecular-mediated interactions may provide new insights into organic/inorganic reactions that involve electrostatic disturbance