Label-free electrochemical detection of HepG2 tumor cells with a self-assembled DNA nanostructure-based aptasensor

Abstract The development of rapid, sensitive and convenient methods for the monitoring of rare circulating tumor cells (CTCs) is of great significance in cancer diagnostics and therapy. Herein a label-free and competitive electrochemical aptasensor was proposed for the efficient capture, ultrasensitive detection and controlled release of CTCs. Firstly, the DNA nanotetrahedron (NTH)-based TLS11a aptamer probe was immobilized on a disposable screen-printed gold electrode (SPGE) surface via the Au−S bonds for the highly enhanced capture of liver cancer HepG2 cells. Then, hybrid nanoprobes of Pd-Pt nanocages labeled with complementary DNA (cDNA), hemin/G-quadruplex DNAzyme and horseradish peroxidase (HRP) were attached on the SPGE substrate by the DNA hybridization, resulting in the formation of dendritic structure (DS) nanoprobes with self-assembly methods for the greatly enhanced sensitivity. When the target HepG2 cells existed, they can compete with DS nanoprobes to bind with NTH-based aptamer probe, resulting in the release of the DS nanoprobes from the SPGE. This method exhibits ultrahigh selectivity and sensitivity toward HepG2 with detection limits of 5 cells per ml. Furthermore, our strategy allows for easy detachment of the captured cells from the SPGE without compromising cell viability by an electrochemical cleavage of the Au–S bonds. The present study provides a label-free technique for highly selective and efficient quantification of tumor cells, which is essential in the early cancer diagnosis and treatment of cancer.