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Connective tissue growth factor (CTGF) is a disease marker of rheumatoid arthritis (RA), and its rapid and sensitive detection is essential for the diagnosis of RA. In this work, a three-dimensional pore structure of alkali-activated nitrogen-doped graphene (aN-G) was used as an electrode modification material, and a label-free electrochemical immunosensor for the sensitive detection of CTGF was successfully constructed by the formation of an amide bond between amino groups in protein and carboxyl groups on the carbon surface. Under optimized conditions, the sensor achieved accurate detection of CTGF in the wide range of 0.0625 ~ 2000 pg mL−1. It had good accuracy (95.0 ~ 100.1%), repeatability (1.2 ~ 2.2%), stability, selectivity, and a low limit of detection (0.0424 pg mL−1, S/N = 3). The sensor was used in serum samples of patients with RA, and CTGF was also successfully detected. Based on this, the electrochemical sensor is expected to become an effective method for RA diagnosis and treatment effect evaluation. [ABSTRACT FROM AUTHOR]

Scheme The construction process of flexible immunosensor for DCNP1. [Display omitted] • A selective quantitative detection method for depression marker DCNP1 was established for the first time. • The construction of the label-free flexible immunosensor is facile, and the required detection time is short. • Pioneering application of NG/TiO 2 in the construction of immunosensors. • The developed immunosensor features a satisfactory linear range, low detection limit, excellent reproducibility, selectivity, and stability. • The constructed immunosensor has been successfully used to determine DCNP1 in brain tissue homogenate samples. In this work, a label-free flexible immunosensor for selective and sensitive detection of dendritic cell nuclear protein-1 (DCNP1), a newly discovered potential marker of depression, was successfully constructed. At first, a highly conductive nanomaterial nitrogen-doped graphene with titanium dioxide (NG/TiO 2) was prepared using a one-pot method, and it was used as an electrode modification material in the construction of immunosensors for the first time. NG/TiO 2 was functionalized with 1-pyrene-butyric acid N-hydroxysuccinimide ester (PSE), and then the DCNP1 antibody could be better immobilized on the surface of the modified indium tin oxide-polyethylene terephthalate (ITO-PET). Then bovine serum albumin (BSA) was used to block non-specific active sites, and the immunosensor (BSA/anti-DCNP1-PSE/NG/TiO 2 /ITO-PET) can be obtained. The fabricated NG/TiO 2 and the construction process of the immunosensor were characterized by scanning electron microscopy, infrared spectroscopy, cyclic voltammetry, and electrochemical impedance methods. Differential pulse voltammetry (DPV) was used to measure different concentrations of DCNP1 after optimizing the ratio of NG and TiO 2 , the modification amount of NG/TiO 2 , the ratio of NG/TiO 2 to PSE, the concentration of anti-DCNP1 and its immobilization time, the concentration of BSA, and the incubation time of DCNP1. The constructed sensor had a wide linear range of 1 ∼ 104 pg mL−1, and a low detection limit of 0.45 pg mL−1 (S/N = 3). It had good reproducibility (RSD = 1.90 %), repeatability (RSD = 2.6 %), and selectivity. After storing it at 4 ℃ for 15 days, its performance decreased to 92.37 %. And it had been successfully used to determine DCNP1 in the brain homogenate of mice with depression induced by chronic unpredictable mild stress (CUMS), providing a possible method for the rapid and accurate determination of DCNP1. [ABSTRACT FROM AUTHOR]

Abstract The porous graphene functionalized black phosphorus composite (PG-BP) was successfully synthesized via strong coherent coupling between porous graphene surface plasmons and anisotropic black phosphorus localized surface plasmons by the method of penetration of infrared ray using infrared drying. And it was used to fabricate a novel high-sensitive electrochemical sensor for determination of bisphenol A (BPA) in daily use and biological samples. The PG-BP had been characterized by infrared spectroscopy, Raman, X-ray photoelectron spectroscopic, scanning electron microscopy and energy dispersive spectrometer, indicating that PG-BP with the large specific surface area and good electrical conductivity was successfully prepared. In addition, electrochemical properties of the modified materials are comparably explored by means of impedance spectroscopy and cyclic voltammograms. Under the optimal conditions, BPA was determined quantitatively using differential pulse voltammetry. The results showed that the BPA detection current has a good linear relationship in the range of 4.3 × 10−8–5.5 × 10−5 mol/L with a detection limit of 7.8 × 10−9 mol/L (S/N = 3). Results from the present work illustrate the prominent performance of PG-BP as a sensing channel for BPA sensor application and the huge potential of PG-BP as an electrode material. Graphical abstract Schematic representation of PG-BP/GCE fabrication and electrochemical detection of BPA. Unlabelled Image Highlights • The PG-BP were successfully prepared based on the strong coupling between porous graphene and black phosphorus. • This is the first research on the electrochemical sensors based on PG -BP composite. • The proposed electrochemical sensor exhibited a broad detection range and low detection limit for BPA. • The electrochemical sensor can be used for the sensitive and efficient analysis of BPA in real samples. [ABSTRACT FROM AUTHOR]

In this study, polyaniline functionalized graphene quantum dots composite with excellent performance was successfully prepared by situ polymerized, and it was applied to fabricate electrochemical sensor for analysis of calycosin in the complex samples of traditional Chinese medicine. The polyaniline functionalized graphene quantum dots composite was characterized by Fourier transform infrared spectroscopy and Raman analysis, to indicate that polyaniline functionalized graphene quantum dots composite was successfully synthesized. The morphology and microstructure of the modified electrodes were characterized by Scanning electron microscope and Transmission electron microscope. According to the results of cyclic voltammetry and electrochemical impedance spectroscope, the glassy carbon electrode modified with polyaniline functionalized graphene quantum dots composite significantly increased the electron transfer rate on the surface of sensor. Under the optimized conditions, the fabricated sensor was used for the analysis of calycosin in Radix Hedysari and Radix Astragali by differential pulse voltammetry, which displayed acceptable reproducibility, long-term stability, good selectivity and sensitivity. The proposed sensor exhibited a wide detection range (1.1 × 10 −5 –3.52 × 10 −4  mol/L) with a detection limit of 9.8 × 10 −6  mol/L (S/N = 3). This study provided a novel and convenient method for rapid evaluation of the quality of Radix Hedysari and Radix Astragali . [ABSTRACT FROM AUTHOR]

Formononetin is an isoflavone compound found in many traditional Chinese medicines that has a wide range of pharmacological activities. It is critical to develop a sensitive, accurate, and rapid determination method for in-depth formononetin research. A molecularly imprinted electrochemical sensor was constructed in this study. After the flexible electrode (ITO-PET) was modified with nitrogen-doped graphene (NG), the molecularly imprinted polymer (MIP) was electropolymerized on the surface using o-phenylenediamine (OPD) as the functional monomer and formononetin as the template. Under optimized experimental conditions, the MIP sensor detected formononetin selectively in 0.1 M phosphate buffer solution (PBS) with the linear range of 3 ~ 120 μM, a detection limit as low as 1.14 μM (S/N = 3), and good anti-interference ability and reproducibility. The analytical performance of the proposed MIP/NG/ITO-PET was evaluated for the detection of formononetin in real samples such as methanol extract of Radix Astragali and mouse plasma with good accuracy and precision. [Display omitted] • A molecularly imprinted electrochemical sensor was established for the selective determination of formononetin for the first time. • The MIP is electropolymerized using OPD as the functional monomer and formononetin as the template. • The constructed MIP/NG/ITO-PET was successfully applied in complex systems such as astragalus extract and mouse plasma. • MIP/NG/ITO-PET has a broad linear range of 3 ~ 120 μM, with a low detection limit of 1.14 μM and good selectivity. [ABSTRACT FROM AUTHOR]

A sensitive electrochemical sensor based on bovine serum albumin (BSA)/poly (diallyldimethylammonium chloride) (PDDA) functionalized graphene nanosheets (PDDA-G) composite film modified glassy carbon electrode (BSA/PDDA-G/GCE) had been developed to investigate the oxidative protein damage and protections of protein from damage by flavonoids. The performance of this sensor was remarkably improved due to excellent electrical conductivity, strong adsorptive ability, and large effective surface area of PDDA-G. The BSA/PDDA-G/GCE displayed the greatest degree of BSA oxidation damage at 40 min incubation time and in the pH 5.0 Fenton reagent system (12.5 mM FeSO 4 , 50 mM H 2 O 2 ). The antioxidant activities of four flavonoids had been compared by fabricated sensor based on the relative peak current ratio of SWV, because flavonoids prevented BSA damage caused by Fenton reagent and affected the BSA signal in a solution containing Co(bpy) 3 3 + . The sensor was characterized by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and scanning electron microscopy (SEM). UV–vis spectrophotometry and FTIR were also used to investigate the generation of hydroxyl radical and BSA damage, respectively. On the basis of results from electrochemical methods, the order of the antioxidant activities of flavonoids is as follows: (+)-catechin > kaempferol > apigenin > naringenin. A novel, direct SWV analytical method for detection of BSA damage and assessment of the antioxidant activities of four flavonoids was developed and this electrochemical method provided a simple, inexpensive and rapid detection of BSA damage and evaluation of the antioxidant activities of samples. [ABSTRACT FROM AUTHOR]