Glass Nanopore Detection of Copper Ions in Single Cells Based on Click Chemistry

As a common redox metal ion pair in cells, copper ions (Cu²⁺/Cu⁺) often transform between oxidation (Cu²⁺) and reduction (Cu⁺) states. They play important roles in the redox process, so monitoring the change of intracellular copper ions helps understand the redox balance and events in cells. In this study, by self-assembling a thiolated ssDNA (with an alkyne end group) onto a gold-coated glass nanopore (G-nanopore) via the Au-S bond, an alkyne-end single-stranded DNA (ssDNA)-functionalized G-nanopore sensing platform (AG-nanopore) was developed to detect copper ions in cells. In the presence of Cu²⁺ or Cu⁺, the introduction of another ssDNA with an azide group will be ligated with an alkyne group on the functionalized nanopore via a copper-catalyzed azide-alkyne 1,3-cycloaddition (CuAAC) click reaction and hence cause the change of the rectification behavior of the AG-nanopore. The rectification ratio variation of the AG-nanopore had a good response to the intracellular copper ion concentration, and the sensing platform was further applied to the study of the relationship between intracellular oxidative stress and the value of Cu²⁺/Cu⁺.