Synthesis of Ag@carbonized Polymer Dots and their Electrochemical Sensing of miRNA

Polyethyleneimine (PEI) is a cationic polymer with a lot of amino groups in its molecular structure that is secure, sterile, and biocompatible. However, it is difficult for PEI molecules to be directly applied in electroanalysis due to their poor electroactivity. Herein, the PEI-based carbonized polymer nanodots (CPDs) with core-shell structure were prepared by hydrothermal method using PEI as the precursors. The results showed that the as-prepared PEI-based CPDs can not only exhibit the unique properties of carbon nanodots but also inherit the properties of PEI. Subsequently, based on the strong coordination interaction between the abundant amino groups on the surface of PEI and silver ions, the electroactive Ag@carbonized polymer dots (Ag@CPDs) were prepared. Furthermore, to investigate the electrochemical behaviors and application of Ag@CPDs, the DNA molecule (double-stranded and single-stranded DNA) was taken as an example. It was found that the interaction of DNA with Ag@CPDs had a significant influence on the current intensity of Ag@CPDs. Based on this phenomenon, a sensitive electrochemical technique for miRNA detection was established and effectively employed to detect miRNA in human serum samples based on the discriminating effect of Ag@CPDs towards ssDNA probes and ssDNA probe/miRNA complex (dsDNA).