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 (N ¹,N ¹-bis(2-aminoethyl)-N ²-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 × 10⁵ 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.