Self-assembled gold nanocrystal micelles act as an excellent artificial nanozyme with ribonuclease activity

Water-soluble Au nanocrystal (NC) micelles with an inserted catalytic Cu(II) center that act as excellent nanoenzyme models for imitating ribonuclease were constructed by supramolecular self-assembly. The dodecane-1-thiol-based Au NC was constructed first, and subsequently the cationic surfactant hexadecyltrimethylammonium bromide and the catalytic ligand (N1,N1-bis(2-aminoethyl)-N2-dodecylethane-1,2-diamine) copper(II) were installed on the surface of the Au NC via hydrophobic interaction. The catalytic capability of the Au NC micelles designed was estimated by the cleavage of a typical RNA analogue, 2-hydroxypropyl p-nitrophenyl phosphate (HPNP). The study of the catalytic behavior of Au NC micelle catalysis showed that the Au NC micelles exhibited dramatic ribonuclease-like activity: a high rate acceleration of k(cat)/k(uncat) = 1.10 x 10(5) for the cleavage of HPNP in comparison with the spontaneous cleavage of HPNP (k(uncat)) was observed. The catalytic capability for HPNP cleavage by these functionalized Au NC micelles can be compared with that of covalent Au nanoparticles reported previously as nanozymes under comparable conditions. A detailed investigation of enzymatic kinetics was carried out and a possible mechanism was suggested.