Thyroid-stimulating hormone detection by a novel electrochemical aptasensor based on foldable origami hybrid electrode constructed from stone paper and SnO2 NPs-modified carbon cloth as a contamination-free platform.

Thyroid-stimulating hormone (TSH) is recognized as one of the most sensitive biomarkers for diagnosis and monitoring of thyroid dysfunction, including hypothyroidism and hyperthyroidism. Accordingly, the design and development of rapid, sensitive, accurate and accessible diagnostic methods for measuring this hormone are of particular importance. In this study, a label-free and paper-based electrochemical aptasensor with an origami structure was designed and fabricated for TSH detection. Reference and counter electrodes were prepared using graphite ink via a stencil-based hand-printing method on a stone paper substrate. Furthermore, the working electrode was made of carbon cloth (CC) and its surface was modified with tin dioxide nanoparticles (SnO2 NPs) synthesized via a hydrothermal method, then placed within the origami structure for immobilization of aptamer. The origami design allowed the working electrode to be physically separated from the reference and counter electrodes during the biofunctionalization steps; thereby preventing surface contamination of these electrodes and improving the stability and performance of the prepared aptasensor. The developed aptasensor was able to detect TSH in the concentration range of 0.001 to 150 μIU/mL with a very low limit of detection of 0.0003 μIU/mL using square wave voltammetry method (SWV). This sensor also showed high selectivity against other thyroid hormones and its efficiency was confirmed in real blood serum samples with a recovery rate of 97 to 103%. The proposed aptasensor with its high sensitivity, low fabrication cost, portability and ease of use can be used as a practical tool for rapid and point-of-care diagnosis in monitoring thyroid disorders.