A MoS2–Au nanoparticle-modified immunosensor for T3 biomarker detection in clinical serum samples

Abstract

A label-free and highly sensitive impedimetric sensor was developed based on electrodeposited molybdenum disulfide (MoS2)-gold (Au) nanoparticles for the detection of total triiodothyronine (T3) in human serum samples. The first step was the electrodeposition of MoS2 and Au on ITO substrates followed by the formation of a monolayer of dithiobis(succinimidyl propionate) (DSP) for binding of T3 antibodies (anti-T3) through coordination of amine coupling to form Au–MoS2/anti-T3 electrode transducers. The resulting film was characterized by SEM-EDS, XRD, FT-IR spectroscopy and electrochemical methods. The electrode kinetics of both MoS2 and Au–MoS2 electrodes were examined through impedance and cyclic voltammetry techniques. The impedance sensor was applied for the label-free detection and quantification of T3 via impedimetric measurements. The T3 binding on the SAM layer on the hybrid electrodes was examined through electrochemical impedance spectroscopy (EIS), and the relative change in the charge transfer resistance was used to quantify T3 in both serum and PBS samples. A linear quantification of T3 was obtained in the range of 0.01–100 ng/mL with a detection limit of 2.5 pg/mL. Also, to test the selectivity, Au–MoS2/anti-T3 electrodes were incubated with similar types of thyroid biomarkers (TSH and cortisol), which did not exhibit non-specific reactions with the transducer surface. Moreover, the sensor has been applied to real samples from healthy individuals and patients diagnosed with cancer and was compared with conventionally available methods.