Study On Rapid Determination Of Arsenic And Mercury Based On Aptamer Technology

The problem of arsenic and mercury pollution in water has became extremely serious in China, where has arsenic-rich and mercury-rich mineral resources and their untreated waste massively discharge into water after exploitation and utilization. Particularly, there are quite many water source in China, which makes it difficult to effectively monitor arsenic and mercury levels in water solely relying on instruments. Therefore it is especially critical to develop some simple,rapid and sensitive assay for on-site detection arsenic and mercury in water. Aptamers are single-strand RNA or DNA oligonucleotides with unique conformations that can specifically bind to their targets. Because they own high specificity, good stability and easy synthes is and mo dification, aptamers have attracted considerable attentions from researchers around the world in recent years, expecially, have demonstrated a good prospect in the area of analytical testing. Herein, we build some simple colorimetric and fluorescent method associated the property of aptamers specifically recognizing targets with novel nanoparticles or nanomaterials, which holds great potential for rapid and on-site detection arsenic and mercury in water. The major contents are summarized below:(1) A colorimetric method based Ars-3 aptamer has developed for the ultrasens itive detection of As(III) in aqueous solution via aggregating gold nanoparticles(AuNPs) by the special interactions between aptamer, target and cationic surfactant. Hexadecyl-trimethylammonium bromide(CTAB), a cationic surfactant, has positive charge in its head, which not only can assemble DNAs to form some supramolecule by electrostatic interaction but also can aggregate Au NPs by destroying the balance of AuNPs. In the absence of As(III), the Ars-3 aptamers are free and can assemble to form a supramolecule structure with CTAB, thus the subsequent AuNPs can not aggregate owing to the lack of CTAB and stay red. On adding As(III), the Ars-3 aptamers is exhausted firstly due to the formation of aptamer-As(III) complex, so that the subsequent CTAB can aggregate AuNPs, which lead to the remarkable change in color from wine red to blue. The method exhibited high selectivity and good sensitivity, and can detect the concentration of As(III) in the range of 0~1500 ppb, with the recovery of 94.6%~124% and a detection limit of 40 ppb for naked eyes or 0.6 ppb for colorimetric assay.(2) A “turn-off” fluorescent method based Ars-3 aptamer has developed for the detection of As(III) in aqueous solution via quenching fluorescence by graphene oxide(GO). A short FAM-labled ss DNA has been designed, which could hybridize Ars-3 aptamer to form a partial ds DNA. In the absence of As(III), the partial ds DNA can not absorb on the surface of GO, thus the labled fluorescent molecules still have great fluorescence. On adding As(III), the Ars-3 aptamers is separated firstly from ds DNA probe due to the formation of aptamer-As(III) complex, thus the short FAM-labled ss DNA can be captured and its fluorescence is certainly quenched by GO. The sensing method can detect the concentration of As(III) in the range of 0.1~100 ppb, with a detection limit of 0.37 ppb.(3) A “turn-on” fluorescent method has been build for the detection of Hg2+ in aqueous solution based on a FAM-labeled ss DNA at its 5’-end and graphene oxide, in which FAM-labeled ss DNA can specifically capture mercury and graphene oxide owns high fluorescence quenching ability and different affinity to ss DNA and T-Hg2+-T complex. In the absence of Hg2+, the FAM-T12 are single strand and easy to be adsorbed on the surface of subsequent GO via π-π stacking interactions and their fluorescence are certainly quenched by GO. Upon addition of Hg2+, the FAM-T12 and Hg2+ can quickly and specifically form T-Hg2+-T complex, which show weak binding on GO surface, thus the labled fluorescent molecules still have great fluorescence. The proposed method can detect the concentration of Hg2+ in the range of 0.1~100 ppb, with the recovery of 90.4%~112% and a detection limit of 0.3 ppb.