Fabrication of electrochemical biosensor composed of multi-functional DNA/rhodium nanoplate heterolayer for thyroxine detection in clinical sample

Thyroxine (T4) contains four iodine atoms and is a major thyroid hormone synthesized in the thyroid gland. Abnormal levels of T4 in the body cause various endocrine diseases. The present study describes the fabrication of an electrochemical biosensor composed of a multi-functional DNA structure/rhodium nanoplates heterolayer for precise detection of T4 concentration. A DNA 3-way junction (3WJ) structure was designed as a multifunctional bioprobe to perform several functions (including target detection, electrochemical signal reporting, and immobilization) simultaneously. Binding between T4 and the T4 DNA aptamer was confirmed through enzyme-linked aptamer assays (ELAAs) and filtration experiments. The multi-functional DNA was immobilized on porous rhodium nanoplates (pRhNPs)-heterolayer modified Au micro-gap electrode. The pRhNPs provided an increment in the surface area and amplification of the electrochemical signal. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were used to detect T4. Under optimal conditions, the limit of detection of T4 was found to be 10.33 pM. Furthermore, up to 11.41 pM of T4 could be detected in clinical samples. This study demonstrates the possibility of label-free detection of the T4 with multi-functional DNA/pRhNPs heterolayer that can be applied to small molecule detection platform in the near future.