Whereas, there was covered with catalytically active sites in the edge plane with high surface energy (Tan et al., 2015). The previous study demonstrated that the basal plane of MoS 2 was catalytically inert. Recently, considerable attention has been drawn to Molybdenum disulfide (MoS 2) as the typical representatives of transition metal dichalcogenides in the field of nanoelectronics (Radisavljevic and Kis, 2013), because of its fantastic electronic and physical properties and promising applications in electrocatalysis, photocatalysis, supercapacitors, lithium-ion batteries, and chemical sensors (Maitra et al., 2013, Wang et al., 2013). To detect biomarkers, immunosensors demand a highly conductive and catalytic substrate by an easily constructed protocol. Therefore, the electrochemical immunosensor, based on the highly antigen-antibody specific interaction, has attracted extensive attention, due to its advantage of high sensitivity and specificity, fast response, ease of operation, easy miniaturization, and simple instrumentation (Han et al., 2016, Jiang et al., 2015, Li et al., 2015). Nonetheless, some of the analytical strategies have been too cumbersome, time-consuming, and expensive, hindering the universal detection of insulin. Therefore, it is significant to propose a highly sensitive and specific strategy for highly electrocatalytic activity toward the reduction of H 2O 2 to achieve the diagnosis of insulin in clinical analysis.Īs the rapid development of analytical technique, more and more methods have been used to diagnose the insulin, such as high performance liquid chromatography (HPLC) (Mercolini et al., 2008), enzyme-link immunosorbent assays (ELISA) (Heyduk et al., 2010), flow injection analysis (Salimi et al., 2009), turbidimetry (Jasuja et al., 2012), and so forth. Hydrogen peroxide (H 2O 2) is not only of great significance in the fields of bioanalysis as well as clinical, pharmaceutical, and environmental applications but also playing a momentous role in regulating various biological processes, including vascular remodeling, immune cell activation, and apoptosis, as a byproduct of large-scale biological processes (Wang et al., 2013). If insulin dysfunctions, it will trigger diabetes mellitus and heighten the risk of kidney failure, myocardial infarction, obesity, and neurodegenerative disease in patients with diabetes and hyperinsulinemia (Schutte et al., 2015, Wang et al., 2018). Once insulin diffused to the human brain, learning and memory can be promoted, especially for verbal memory (Benedict et al., 2004). More importantly, insulin can also affect vascular cognition and compliance. Meanwhile, circulating insulin can influence proteins synthesis in widely various tissues (Saltiel and Kahn, 2001). For example, a high concentration of insulin in the blood strongly inhibits the production and secretion of hepatic glucose (Zhu et al., 2017). It not only promotes absorption of glucose from the blood into adipocytes, liver and skeletal muscle cells but also regulates the metabolism of carbohydrates, fat, and protein. Insulin, a peptide hormone produced by pancreatic islet beta cells, is regarded as the key anabolic hormone in vivo (Hsieh et al., 2006). Characterized by good reproducibility, specificity, and stability, the fabricated immunosensor may blaze a path for insulin detection in a real sample. Under the optimal conditions, the proposed immunosensor exhibited a sensitively linear relation with logarithmic insulin concentrations from 0.01 to 100 ng/mL with a low detection limit of 3.0 pg/mL (S/N = 3). Especially, SEM, TEM, and XPS information further confirmed nanomaterial's surface morphology and amorphous structure. Attributed to the excellent property, electrochemical signals could be greatly amplified, contributing to improving detection sensitivity. Furthermore, Pd MoS x with favorable biological compatibility can conjugate a great many antibodies to capture insulin. In this work, Pd MoS x prepared in the presence of CTAB possessed an excellent catalytic activity for the reduction of H 2O 2. Here, a novel H 2O 2 -based electrochemical immunosensor utilizing Pd nanoparticles functionalized three-dimensional wrinkly amorphous MoS x composites (Pd MoS x) as the platform was developed for the determination of insulin.
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