Abstract
This paper reports a biosensor based on a MoS2-graphene (MG) composite that can measure the parathyroid hormone (PTH) concentration in serum samples from patients. The interaction between PTH and MG was analysed via an electrochemical sensing technique. The MG was functionalized using l-cysteine. Following this, PTH could be covalently immobilized on the MG sensing electrode. The properties of MG were evaluated using scanning electron microscopy, high-resolution transmission electron microscopy, X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, and Fourier transform infrared spectrometry. Following optimization of immobilized materials—such as MG, PTH, and alkaline phosphatase (ALP)—the performance of the MG sensor was investigated via cyclic voltammetry, to assess its linearity, repeatability, and reproducibility. Electrochemical impedance spectroscopy was performed on graphene oxide (GO) and MG-modified electrodes to confirm the capture of a monoclonal antibody (MAb) targeting PTH. Furthermore, the ALP-PTH-MG sensor exhibits a linear response towards PTH from artificial serum over a range of 1–50 pg mL−1. Moreover, patient sera (n = 30) were evaluated using the ALP-PTH-MG sensor and compared using standard equipment (Roche E 170). The P-value is less than 0.01 when evaluated with a t-test using Welch’s correction. This implies that the fabricated sensor can be deployed for medical diagnosis.
Highlights
Enzymes such as horseradish peroxidase (HRP) on its surface
scanning electron microscopy (SEM) confirmed that the MG composite was formed successfully by Gr self-assembly during the hydrothermal process (Fig. 1a)
During the hydrothermal process graphene oxide (GO) was reduced to Gr, and coalesced particles of the MG composite were formed with a composite particle size of 1 μm[28]
Summary
Nyquist plots were obtained for the modified electrodes at different PTH concentrations, with ALP in AAP substrate (Fig. 3d). We infer from this that the results obtained from the fabricated AP-MG sensor are in good agreement with those of the standard measurement device, E 170 This suggests the possibility of applying the AP-MG sensor to detect the concentration of PTH in human serum samples. The AP-MG sensor performed well, with high sensitivity and reproducibility, when PTH concentrations in artificial serum samples were analysed by cyclic voltammetry within a linear range of 1–50 pg mL−1. Differences between the PTH concentrations measured using the AP-MG sensor, and those measured using the standard device, E 170, were statistically analysed using an unpaired t-test with Welch’s correction This analysis revealed a high correlation with E 170 (R2 > 0.95; P < 0.01). The fabricated AP-MG sensor exhibited similar levels of accuracy and performance relative to E 170 for its ability to analyse PTH concentrations in serum samples from patients
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