Synthesis Of Palladium-Based Nanozyme And Its Application On The Sensing Of Sulphur-Containing Substances

Cysteine?Cys?and homocysteine?Hcy?are the most common biothiols in living organisms.Cys at a deficient level is related with slowed growth,liver damage and edema.An increased level of Hcy is an isolated risk factor causing the development of dementia,Alzheimer's disease as well as cardiovascular diseases.Therefore,it is of great importance in the sensing of Cys and Hcy.Sulfideanions(S^2-)play an important role within bio-geochemical processes.Nevertheless,it is strongly toxic.The presence of excess sulfideanions in aqueous systemsdo harm to ecosystem and human survival.Therefore,the sensitive and rapid detection of S^2-is particularly important.In this work,by usingcytosine-richoligonucleotides d(C₁₀)and nucleic acid monomer guanosine 5'-single phosphoric acid disodium salt?GMP?as templates,two kinds of palladium-based nanozymes with intrinsic peroxidase-like activity are synthesized and applied in the colorimetric detectionfor sulfur-containing substances.Firstly,cytosine-rich oligonucleotides d(C₁₀)are used to stabilize Pd-basedenzymatic nanoparticles with a size distribution of 3.7-5.1 nm,with different surface charge conditions and peroxidase mimicking activities.The d(C₁₀)-Pd nanozyme with an average diameter of 4.8 nm possesses the K_m value of 0.033 mM toward TMB and 91.29 mM toward H₂O₂.On the basis of thiol-induced shielding of peroxidase-like activity of d(C₁₀)-Pd,Pd-based nanozyme is employed for the the sensitive detection of biothiols including Cys and Hcy.The limits of detection are 3.7 nM for Cys and 4.3 nM for Hcy.And the linear ranges are 10-150 nM for Cys and 20-300 nM for Hcy,respectively.This Pd-based peroxidase nanomimetic exhibits a promising application in quantitative detection of thiol-containing compounds in biological fluids.Secondly,GMP is used to stabilize Pd-based enzymatic nanoparticles with a size distribution of 4.9-7.4 nm,with different peroxidase mimicking activities.The GMP-Pd nanozyme with an average diameter of 5.5 nm possesses the K_m value of 0.176 mM toward TMB and 39.76 mM toward H₂O₂.On the basis of sulfideanion-induced inhibition of peroxidase-like activity of GMP-Pd,Pd-based nanozyme is employed for the the sensitive detection of S^2-,with the limit of detection of 1.8 nM and linear range of 5-60 nM.