Construction Of Bifunctional Biosensing Platform P-DNA@MOF For The Selective Detection Of Hg²⁺,Ag⁺ And Biothiols

Mercury ions(Hg2+)and silver ions(Ag+)are a wide range of contaminants with serious toxicity,which are hardly degraded naturally in the environment and are easily accumulated in the human body through the food chain.Even at low concentration,chronic exposure can also be harmful to human health,especially to the central nervous system.On the other hand,the abnormal expression of thiols,including cysteine(Cys),glutathione(GSH)and homocysteine(Hcy)in the body,is also associated with many diseases of the central nervous system.Therefore,it is of great significance to construct a suitable sensing platform with high sensitivity and selectivity for the simultaneous detection of Hg2+,Ag+ and biothiols.In this thesis,three novel water-stable metal organic frameworks(MOFs)1,2 and 3 have been constructed using quaternized-carboxylate ligands with Cu(Ⅱ).Among them,MOF 1 has a three-dimensional structure,MOF 2 has a one-dimensional zwitterionic chain structure,and MOF 3 has a two-dimensional grid structure.On the surface of these MOFs are enriched with Cu2+,the positive charges of quaternary ammonium salts and the fused rings from ligands.These structural features enable them to form sensing platforms with metal ion-specific probe DNA(P-DNA)via electrostatic,hydrogen bonding,and π-π stacking interaction to construct a P-DNA@MOF sensing platform,these platforms may find applications in the continuous detection of metal ions and biothiols.Based on MOF 1,a mercury ion sensor P-DNA-1@1 was constructed with FAM-labeled thymidine(T)-rich single-stranded probe DNA(P-DNA-1),followed by addition of mercury ions to further construct a T-Hg2+-T biothiols sensor l+ds-DNA-1@Hg2+.The detection limits of Hg2+,Cys,GSH and Hey were 2.4 nM,13.2 nM,11.1 nM and 8.5 nM,respectively.Based on MOF 2,a silver ion sensor P-DNA-2@2 was constructed with TAMRA-labeled cytosine(C)-rich single-stranded probe DNA(P-DNA-2),followed by addition of silver ions to further construct C-Ag+-C biothiols sensor 2+ds-DNA-2@Ag+.The detection limits of Ag+,Cys,GSH and Hey were 5.3 nM,14.2 nM,13.5 nM and 9.1 nM,respectively.Based on MOF 3,a dual-sensing platform of P-DNAs@3 was constructed with FAM-labeled T-rich single-stranded probe DNA(P-DNA-1’)and TAMRA-labeled C-base-rich single-stranded probe DNA(P-DNA-2),this sensor can be used for the simultaneous detection of mercury ions and silver ions using the constant-wavelength synchronous fluorescence technology.The detection limits for Hg2+ and Ag+ were 2.6 nM and 7.5 nM,respectively.