The Design And Application Of SERS Sensing Analysis System Via DNAzyme

In this work,a simple and novel DNAzyme-based SERS quadratic amplification method is developed for the detection of Pb²⁺.This strategy possesses some remarkable features compared to the conventional DNAzyme-based SERS methods,which are as follows:（i）Coupled DNAzyme-activated hybridization chain reaction（HCR）with bio barcodes;a quadratic amplification method is designed using the unique catalytic selectivity of DNAzyme.The SERS signal is significantly amplified.This method is rapid with a detection time of 2 h.（ii）The problem of high background induced by excess bio barcodes is circumvented by using magnetic beads（MBs）as the carrier of signal-output products,and this sensing system is simple in design and can easily be carried out by simple mixing and incubation.Given the unique and attractive characteristics,a simple and universal strategy is designed to accomplish sensitive detection of Pb²⁺.The detection limits of Pb²⁺via SERS detection is 70 fM,with the linear range from 1.0×10^-13 M to 1.0×10^-7 M.A simple and novel DNAzyme-based SERS quadratic amplification method is developed for the detection of Pb²⁺.In the presence of Pb²⁺,a DNA-Pb²⁺complex are formed.The complex can perform a catalytic reaction that is the cleavage of the substrate strand at the scissile ribonucleic acid adenosine（rA）The substrate is cleaved,the separated duplex regions lack thermal stability,and the trigger strand region is released into the solution.Trigger strand is complementary to the loop of the block DNA.Through the strand binding with trigger strand,the hairpin structure of the block DNA is opened.The initiate strand of the stem is unlocked;then H1 serves as an initiator to trigger the HCR reaction.A chain reaction of alternating kinetic escapes by the two hairpin species（H2 and H3）correspond to“polymerization”into a nicked double helix.The sticky ends of H2 and H3 are complementary to the capture DNAs（C1）of Rox-bio barcode（the sequence of the stick end is shown in Table S1）,so abundance of SERS bio barcodes is attached to MB.Thus,Pb²⁺could be detected quantitatively by measuring the Raman signal of Rox attached on MB after quadratic signal amplification through the combination of the bio barcode and HCR after magnetic separation.A simple and novel DNAzyme-based SERS quadratic amplification method is developed for the detection of Pb²⁺,to assess the lead ion detection efficiency in the practical samples;the experiment was carried out in buffers containing 5%tap water samples or 1%human serum in two diverse concentration levels of 10 nM,100 nM.Each group was repeated three times and the average values were regarded as the result.The detailed recycling results were displayed in Table 1.The average rate of recovery in practical sample kept in ranging from 92%to 96%,while the standard solution recovery was changing from 98%to 102%,with the acceptable variations that the average relative standard deviation wasless than 7%.Therefore,the experimental results indicate that this method could be utilized for the detection of the lead ions in the practical samples with generally satisfactory.