A wireless magnetoelastic sensor for uranyl using DNAzyme-graphene oxide and gold nanoparticles-based amplification

A wireless magnetoelastic sensor (WMS) for uranyl detection has been developed using DNAzyme-graphene oxide (GO) and gold nanoparticles (AuNPs)-based amplification. The WMS is fabricated by immobilizing a layer of GO film on a magnetoelastic ribbon-like sensor. When the substrate strand of DNAzyme was cleaved in the presence of UO22+, the single-stranded DNA (ssDNA) was adsorbed onto the GO film of the WMS, resulting in a decrease of resonance frequency of the WMS. HAuCl4 can be reduced by ascorbic acid (AA) to atom Au coated on AuNPs in cetyltrimethyl ammonium bromide (CTMAB) solution, leading to the signal amplification of the system. When the molar ratio of AA and HAuCl4 was 3:2, the response signals linearly correlated with the concentration of UO22+ over the range of 9.57 × 10−9 to 1.20 × 10−7 M in the MES buffer solution of pH 5.0 with a detection limit of 2.87 × 10−9 M. The proposed WMS has additional advantages of being less time-consuming, low cost and remote query, and avoids the interference of some metals such as Cu2+, Fe2+, Fe3+, Hg2+, and Tb3+. It has been successfully applied for detecting UO22+ in real samples with a satisfactory result. A polyacrylamide gel electrophoresis (PAGE) assay, scanning electron microscopy (SEM) and UV-vis spectra were used to confirm the mechanism for structure switching and signal amplification.