Colorimetric Assay Based On DNA-Ag/Pt Nanoclusters Mimic Enzyme

Many bimetallic nanomaterials were known as the “nanomimic enzymes” for owning excellent catalytic activity,and applied to many fields.Lots of sensor detection methods have been developed and attracted more attention from researchers.Based on a novel DNA-Ag/Pt nanoclusters?NCs?mimic enzyme,colorimetric detection methods for mercury ion,L-cysteine and copper ion were established in this paper.1.A colorimetric method for detection of Hg²⁺ was established.A kind of nanoclusters consisting of Ag+ and Pt²⁺ were induced by NaBH4 with a single strand DNA as the template named DNA-Ag/Pt NCs,which have the peroxdiase-like activity.The activity of DNA-Ag/Pt NCs can be inhibited selectively by Hg²⁺,the interaction between Hg²⁺ and the NCs was discussed through characterization by TEM,DLS,XPS and EPR,etc.It was found that the absorbance at 652 nm was decreasing as the Hg²⁺ concentration increasing from 10 nmol/L to 200 nmol/L,and the linear relationship between the concentration of Hg²⁺ and A652 nm was established for Hg²⁺ with a detection limit of 3.0 nmol/L and a linear range of 10 nmol/L-200 nmol/L.The method was highly selective toward Hg²⁺ over other common metal ions,low-cost and simple,which facilitated the application of detecting Hg²⁺ in tap water.2.A colorimetric method for detection of L-Cys was established.The peroxidase-like activity of DNA-Ag/Pt NCs can be inhibited significantly by L-Cys,and the interaction between this was discussed through characterization by TEM,DLS and CD,etc.It was found that A652 nm was decreasing as the L-Cys concentration increasing from 5.0 nmol/L to 500 nmol/L,and the linear relationship between the concentration of L-Cys and A652 nm was established for L-Cys with a detection limit of 2.0 nmol/L.This method facilitated the detection of L-Cys in biological samples.3.A colorimetric method for detection of Cu²⁺ was established.It was found that MPA can inhibit the peroxidase-like activity of the DNA-Ag/Pt NCs.However,after incubated with Cu²⁺,MPA lost the inhibition toward catalytic activity of NCs.The interaction during Cu²⁺,MPA and NCs was discussed through characterization by TEM,EPR and EDX,etc.It was found that A652 nm was increasing as the Cu²⁺ concentration increasing from 10 nmol/L to 100 nmol/L,and the linear relationship between the concentration of Cu²⁺ and A652 nm was established.Based on this finding,a colorimetric detection for Cu²⁺ was developed with a detection limit of 5.0 nmol/L and a linear range from 10 nmol/L to 100 nmol/L.This method exhibited high sensitivity and selectivity toward Cu²⁺ over a panel of other metal ions,and was also applied to detect real water samples.