Electrochemical immunoassay for one-pot detection of thyroxin (T4) and thyroid-stimulating hormone (TSH) using magnetic and Janus nanoparticles.

Abstract

Concurrent measurement ofthyroid-stimulating hormone (TSH) and thyroxine (T4) hormones profoundly help clinicians diagnose hyper- and hypothyroidism. This work demonstrates the development of a sandwich-type electrochemical immunoassay using Janus and magnetic nanoparticles for one-pot detection of thyroxine (T4) and thyroid-stimulating hormone (TSH). The signaling probe was developed by preparing Janus cadmium (CdO) and zinc oxide (ZnO) NPs decorated by T4/TSH-specific molecularly imprinted polymers (MIPT4-CdO and MIPTSH-ZnO). The capture probe was obtained by coating magnetic Fe3O4 NPs with 1,3-Bis(3-carboxy propyl) tetramethyl disiloxane and activating using N-hydroxy succinimide (NHS) and 1-ethyl-3-(3-dimethyl aminopropyl) carbodiimide (EDC), and finally conjugating with T4/TSH-specific antibodies. To analyze T4 and TSH in actual samples, MIPT4-CdO and MIPTSH-ZnO were added to the sample solutions, and after incubation, capture probes (Fe3O4-AbTSH and Fe3O4-AbT4) were added. An external magnetic field was used to separate the sandwiched nanosystem, followed by adding a dilute solution of nitric acid (HNO3) to dissolve CdO and ZnO NPs and free Cd(II) and Zn(II) cations. The concentration of these cations was determined using constant-current potentiometric stripping analysis (cc-PSA) on screen-printed electrodes (SPE) modified with multi-walled carbon nanotubes (MWCNT). The obtained signals for Cd(II) and Zn(II) were proportional to T4 and TSH concentrations. Limits of detection (LOD) for T4 and TSH analyses were respectively 0.02ng.dL-1 and 0.0002 µU.mL-1 with a linear range of 0.05-50ng.dL-1 and 0.001-100 µU.mL-1. The proposed nanosystem's main advantage is the simultaneous detection of T4 and TSH in clinical samples with high sensitivity, selectivity, and stability.