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Hydrolytic Cleavage of Nerve Agent Simulants by Gold Nanozymes
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1  University of Padova


Nerve agents (phosphate esters and related phosphorus(V) materials) are among the most noxious chemical compounds known to mankind. Although procedures for their destruction as bulk stockpiles are well known, still the research is open for catalysts for the deactivation of limited amounts of such chemicals, particularly for the use when civilians or military personnel are affected. Surface-passivated gold nanoparticles (AuNPs) have been shown to be among the most powerful catalysts for the cleavage of phosphate diesters (including DNA), nevertheless they have never been used for the hydrolysis of nerve agents. In this work, we report our results on the hydrolysis of simulants p-nitrophenyl diphenyl phosphate (PNPDPP) and dimethyl p-nitrophenyl phosphate (DMNP, methyl paraoxon) by 2-nm AuNPs passivated with metal complexes of ligands bearing 1,4,7 triazanonane and 1,4,7,10 tetraazadodecane macrocycles. PNPDPP was used for a quick screening of a small 28-member library constituted by these AuNP in the presence of metal ions Zn(II), Cu(II), Co(II), Co(III), Eu(III), Yb(III) and Zr(IV). We show that the presence of the amide connecting the cyclic polyamine to the tether is detrimental for catalysis. From the screening of this small library we selected the five best performing catalysts and tested them in the hydrolysis of DMNP which is more similar to the real nerve agents. The results indicate that 2 nm gold nanoparticles passivated with a monolayer of thiols functionalized with macrocyclic ligands cleave quite efficiently nerve agent simulants PNPDPP and DMPN as Zn(II) and Cu(II) complexes at room temperature and physiological pH. The half-lives determined for the hydrolytic process are of the order of a few minutes. The mild conditions employed, and the use of metal ions present in many enzymes make them rather appealing nerve agent detoxification catalysts.

Keywords: Gold Nanozymes, Nerve Agent, Macrocyclic ligand, Metal ions