Detection Of Hg²⁺ Based On Electrode Modification And Multiple Amplification Strategies

Heavy metal ions can cause serious diseases and environmental pollution,which has become one of the main problems of global public health.Mercury ion(Hg²⁺)is a kind of highly toxic heavy metal ion.As a highly toxic soluble heavy metal ion,it not only pollutes the environment,but also destroys human metabolism,causing permanent damage to the human central nervous system and immune system,posing a serious threat to the life system.Therefore,it is of great significance to develop a rapid and ultrasensitive method for the determination of Trace Mercury in the environment.In this paper,the detection technology of Hg²⁺was studied by using fluorescence and electrochemical methods through electrode modification,synthesis of high surface area nanomaterials and various nucleic acid signal amplification strategies.（1）Rapid fluorescence detection of Hg²⁺based on magnetic bead and exonuclease III-assisted double cycle amplification reaction:In this study,a rapid fluorescence detection method for Hg²⁺was designed based on magnetic bead separation and exonuclide III-assisted double cycle amplification reaction.First of all,the captured probe labeled with biotin was fixed to a magnetic bead modified with streptavidin.Then it was paired with reporter DNA（RDNA）generated by cyclic amplification of hairpin probe triggered by exonuclide III in the presence of Hg²⁺.Subsequently,the probe DNA was modified by the fluorescence group FAM at one end and the corresponding fluorescence quenching group BHQ1 at the other end,and the probe DNA was complementary paired with part of the RDNA bases.Finally,exonuclide III was added to cut the base paired with RDNA and fluorescent probe,and the second exonuclide III-assisted cyclic amplification reaction was realized,and the effect of fluorescence group FAM signal amplification was finally achieved.（2）An electrochemical biosensor based on electrode modification and triple amplification strategy for ultrasensitive detection of Hg²⁺:we designed a novel Hg²⁺detection electrochemical biosensor based on the triple signal amplification strategy of DNA dual cycle,Cu₃（PO₄）₂ HNFs and Au NP probe.The first strategy of the DNA dual cycle amplification was triggered by Exo III to digest the thymine bases rich（T-rich）DNA formed through T-Hg²⁺-T coordination to release Hg²⁺for the next cycle.Simultaneously,large amounts of report DNA（RDNA）were released to form new double stranded DNA（ds DNA）structure with hairpin 2（HP2）on electrode.Subsequently,the introduction of hairpin 3（HP3）opened the new ds DNA to release RDNA again for the next cycle.After the DNA dual cycle amplification,the special probe was eventually formed on the electrode.Cu₃（PO₄）₂HNFs were synthesized via a facile green synthetic method.Au NPs labeled with c-probe were effectively anchored on the Cu₃（PO₄）₂HNFs（c-probe/Au NPs/Cu₃（PO₄）₂HNFs）,thus improving the distribution homogeneity of Au NPs and improved the efficiency.Then,the c-probe/Au NPs/Cu₃（PO₄）₂HNFs were connected to the probe on the electrode.Finally,Au NPs modified with R-probe（r-probe 1 and r-probe 2 marked with ferrocene）were connected by the c-probe on the Cu₃（PO₄）₂HNFs,resulting in further electrochemical signal amplification.The results suggested that the proposed electrochemical biosensor displayed remarkable amplification efficiency,rapid response,and high sensitivity and selectivity for the detection of Hg²⁺.This strategy was successfully applied to detect Hg²⁺from spiked water sample.