A facile label-free electrochemical aptasensor constructed with nanotetrahedron and aptamer-triplex for sensitive detection of small molecule: Saxitoxin

Abstract

Development of facile electrochemical aptasensors for small molecules is of great significance. Herein, the aptamer technology, DNA nanotetrahedron, DNA triplex, and electrochemistry were combined for the first time to construct a facile label-free electrochemical aptasensor for highly sensitive detection of small molecules. A typical small molecule, saxitoxin (STX, Mw. 299 g/mol), was chosen as a model target. The nanotetrahedron assisted the orientated immobilization of the aptamer- triplex on the surface of screen-printed electrodes, protecting the aptamer-triplex from absorption and entanglement and assisting the aptamer to display full accessibility to STX. Large and sensitive electrochemical signal changes were triggered along with the binding of the aptamer and STX, as the aptamer fold adaptively into specific conformational structure and caused disassembly of the triplex and dissociation of a DNA chain with Mw. exceeding 15,000 g/mol from the electrode. The developed aptasensor provided high sensitivity with a LOD of 0.92 nM and showed good practicability towards STX in real seawater samples, with well-validated recovery data (94.4%–111%), good selectivity, stability and repeatability. This study can be referred for analysis of any other small molecules.