Abstract
Silver, a very common heavy metal, has been employed in electronics, medicine, jewelry, and catalysis due to its excellent chemical and physical characteristics. Silver-containing wastes can cause environmental pollution, so it is vital to monitor the Ag(I) concentration. Here, a label-free biosensor was developed for the Ag(I) detection, which used single-walled carbon nanotubes/field effect transistor (SWNTs/FET) to functionalize with a specific DNAzyme, containing an Agzyme and a complementary strand DNA (CS-DNA) embedded an RNA-base. The CS-DNA was covalently immobilized on the SWNTs’ surface through peptide bonds, and then combined with the Agzyme. When Ag(I) was bound with the Agzyme, the CS-DNA can be cleaved at the RNA site efficiently. The cleaved DNAzyme induced a remarkable change in the electrical conductivity of SWNTs. The performances of DNAzyme/SWNTs/FET were investigated using different spectroscopy and electrochemical methods. Under the optimized parameters, DNAzyme/SWNTs/FET presented a high sensitivity and selectivity towards Ag(I), in which the linear response range is 10 pM to 106 pM and the limit of detection is 5 pM(S/N = 3). Additionally, the prepared biosensor was applied to measure the Ag(I) concentration in the water sample with good results.
Highlights
Heavy metal pollution [1,2] has attracted attention in many developing countries as heavy metals have acute toxicity that threatens human health [3,4]
With unreasonable mining and waste management, untreated pollutants containing silver and its compounds were discharged into the surrounding
Silver emissions from industrial wastes were approximately 2,500 tons every year, of which 80 tons entered surface waters and 150 tons were released into the sludge of wastewater treatment plants [14,15]
Summary
Heavy metal pollution [1,2] has attracted attention in many developing countries as heavy metals have acute toxicity that threatens human health [3,4]. If humans ingested the polluted water and food for a long period, Ag(I) would be accumulated in human body. It might probably cause serious diseases with various symptoms, including stomach pains, breathing problems, lung and throat irritation, a blue-gray discoloration of the skin, and mild allergic reactions [20,21]. The United States Environmental Protection Agency (USEPA) required the Ag(I) concentration in drinking water to not exceed 0.10 ppb [22]
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