Hybridization Chain Reaction-DNAzyme Amplified Switch Micro-plate Assay for Magnesium Ions

Abstract

It is recognized that metal ion contaminants present in food and the environment posed a serious threat to human health and contributed to huge economic losses. Therefore, the development of simple, rapid, sensitive, and on-site methods for the detection of metal ion has become an urgent need. Here, we combined the isothermal hybridization chain reaction (HCR) and DNAzyme to develop a dual signal amplification sensing assay for ultrasensitive Mg2+ detection on microplates. In this assay, the linker DNA strand (LDNA) that triggered the formation of HCR structure was immobilized on a microplate by biotin-streptavidin conjugation. Upon the addition of the substrate strand H5 sequence to form a DNAzyme structure, an amplification switch microplate with 2n signaling amplification sites was established. The HCR-DNAzyme switch was acti-vated by capturing Mg2+and the methylene blue (MB) labeled H5 was released. It generated an electrochemical signal after being captured by the reporter electrode attached with its complementary sequence (CDNA), accomplishing an efficient detection of Mg2+. Moreover, due to the 2n signal amplification of the HCR-DNAzyme system with the simple separation and purification processing of microplate, the detection limit of this strategy for Mg2+ was as low as 0.6 fM. Furthermore, the method could be employed for other targets by simply changing the recognition structure of DNAzyme, revealing the poten-tial practical applications in a wide range of fields.