Electrochemical immunosensor based on Cu(II)-tetrahydroxy-1,4-benzoquinone amplifier for carcinoembryonic antigen determination.

In order to solve the problems of unstable signal and fast decrease of response signal of traditional electroactive substances, we synthesized a new type of electroactive substances, so that they can cooperatively amplify the response signal of the immune sensor and further improve its sensitivity. The conductive organic ligand tetrahydroxy 1,4-benzoquinone (THQ) and Cu2+ were chelated to form a stable polymeric two-dimensional metal-organic framework material Cu-THQ. Cu-THQ is a new type of electroactive substance. Compared with the traditional electroactive substance, Cu-THQ not only has stronger Redox activity, but also better stability and biocompatibility. We carried out various electrochemical characterizations on Cu-THQ and further proved that the introduction of Cu2+ not only greatly enhanced the stability of THQ electrical signal, but also increased its signal response. The experimental results showed that the prepared immunosensor exhibited good linearity for the detection of carcinoembryonic antigen in the range 1 fg/mL to 40 ng/mL, with detection limits and sensitivity of 0.477 fg/mL and 14.81 µA/(ng/mL)/cm2, respectively.

Fabrication of a novel electrochemical immunosensor for the sensitive detection of carcinoembryonic antigen using a double signal attenuation strategy.

Carcinoembryonic antigen (CEA), an acidic protein, is a characteristic antigen produced by the tumor of various cancers (eg, breast, cervical, rectal, lung, etc.). Therefore, the detection of cancer antigens is very important for the early diagnosis and treatment of cancer. In this study, a novel of "signal off" strategy for electrochemical immunosensor was developed to detect CEA. To this end, Prussian blue nanoparticles (PB NPs), an electroactive substance, were used as the immunological platform. In addition, CuO2@SiO2 nanocomposites, which release Cu2+ and H2O2 under acidic conditions, were synthesized. The generated Cu2+ can replace the high spin iron (FeIII) in PB NPs, which in turn reduces the oxidation peak current of PB NPs. Due to the peroxidase-like nature of PB NPs, they can react with self-generated H2O2 to generate hydroxyl radicals (·OH), which can further convert 4-chloro-1 naphthol (4-CN) into a non-conductive polymer that accumulates on the electrode surface, this leads to a further reduction in the electrical signal of the PB NPs. Moreover, the self-generated Cu2+ and H2O2 can reduce the introduction of exogenous substances and improve the detection accuracy. Square wave voltammetry (SWV) revealed that the electrical signal of PB NPs gradually decreased with increasing CEA concentration. In addition, the electrical signal of PB NPs exhibited a good linearity in the range from 0.01 pg mL-1 to 80 ng mL-1, where in the logarithm of CEA concentration and the detection limit was as low as 0.0032 pg mL-1.

An electrochemical immunosensor for the detection of carcinoembryonic antigen based on Au/g-C3N4 NSs-modified electrode and CuCo/CNC as signal tag.

Carcinoembryonic antigen levels in the human body reflect the conditions associated with a variety of tumors and can be used for the identification, development, monitoring, and prognosis of lung cancer, colorectal cancer, and breast cancer. In this study, an amperometric immunosensor with CuCo/carbon nanocubes (CuCo/CNC) as the signal label is constructed. The bimetal-doped carbon skeleton structure has a high specific surface area and exhibits good electrocatalytic activity. In addition, Au/g-C3N4 nanosheets (Au/g-C3N4 NSs) are used to modify the substrate platform, facilitating the loading of more capture antibodies. The reaction mechanism was explored through electrochemical methods, X-ray powder diffraction, X-ray photoelectron spectroscopy, and other methods. Kinetic studies have shown that CuCo/CNC have good peroxidase-like activity. In addition, the electrocatalytic reduction ability of CuCo/CNC on hydrogen peroxide can be monitored using amperometric i-t curve (- 0.2 V, vs. SCE), and the response current value is positively correlated with the CEA antigen concentration. The prepared electrochemical immunosensor has good selectivity, precision, and stability. The dynamic range of the sensor was 0.0001-80 ng/mL, and the detection limit was 0.031 pg/mL. In addition, the recovery and relative standard deviation in real serum samples were 97.7-103 % and 3.25-4.13 %, respectively. The results show that the sensor has good analytical capabilities and can provide a new method for the clinical monitoring of CEA.

Ti3C2 MXene anchors CuAu-LDH multifunctional two-dimensional nanomaterials for dual-mode detection of CEA in electrochemical immunosensors.

Electrochemical immunoassays are commonly used to detect biomarkers and Ti3C2 MXene anchored CuAu-LDH two-dimensional hydroxide heterojunctions for dual-mode electrochemical immunosensors were fabricated in this work. Layered double hydroxides have a large surface area, high chemical stability, tunable metal composition and interchangeable anions, however, the insulating nature of LDH further limits its catalytic performance. For this reason, Ti3C2 Mxenes were introduced to improve this problem. 2D layers of Ti3C2 Mxenes with large specific surface area and excellent conductivity have been well proven and widely used. And the surface of Ti3C2 Mxenes (due to the presence of abundant surface functional groups), will facilitate the anchoring of metal ions and the nucleation of LDH. In addition, its excellent electrical conductivity will facilitate the electron transfer between Cu2+ and Cu+. The immunosensor not only showed a heavy square wave voltammetry (SWV) signal. It also exhibited high electrocatalytic activity for H2O2 redox reactions and improves the sensitivity of the Ampere Current (i-t) detection. The CEA immunosensor developed in this study showed a wide linear response (0.0001-80 ng/mL) and the lowest detection limits (SWV: 33.6 fg/mL and i-t: 45.4 fg/mL S/N = 3). The results confirmed the excellent analytical capability of the immunosensor.

The electrochemical immunosensor of the "signal on" strategy that activates MMoO4 (M = Co, Ni) peroxidase with Cu2+ to achieve ultrasensitive detection of CEA.

A new type of ultrasensitive electrochemical immunosensor with "signal on" strategy was designed for quantitative detection of CEA. The sensing strategy design is based on the following principles: We use HMSNs-Cu2+@HA as the signal probe, the structure of HA is destroyed under acidic conditions, and the released Cu2+ activates the substrate material MMoO4 (M = Co, Ni) Peroxidase activity initiates the reaction of catalytic H2O2 and realizes the "signal on" condition of electrical signals. This strategy has the following advantages: (1) HA coating of HMSNs-Cu2+ can prevent Cu2+ leakage, has good biocompatibility and can be connected with more antibodies. (2) The prepared sensor has the characteristics of high sensitivity and a low detection limit. When the electrode substrate was CoMoO4, the detection range of the immunosensor was 0.01 pg/mL-40 ng/mL, and the detection limit was 0.0035 pg/mL (S/N = 3). This work innovatively applies the catalytic activity of metal ion-activated nanozymes in the detection of CEA, providing a new perspective for the monitoring and analysis of cancer markers.

Pollution characteristics and ecological risks associated with heavy metals in the Fuyang river system in North China.

The Fuyang River system (FRS) in north China, for a long time, is seriously polluted with organic compounds and heavy metals due to industrialization. However, the information on heavy metal pollution in this area is still limited, and health risks raised by trace elements are neglected up to now. To characterize the heavy metal pollutants and assess their potential ecological risks scientifically in FRS, surface sediments were collected from 66 sampling sites selected according to the hydrological and anthropogenic conditions along the river. A total of twelve metal pollutants (e.g., Cr, As, and Hg) in the sediments were detected among the distributaries. A combining application of geoaccumulation index (Igeo), ratio of secondary phase and primary phase (RSP), and the ecological risk factor (Eri) in this study gave systematic assessment results of single or combined pollution status raised by heavy metals in this area. The results show that Cr, Ni, Cu, As, Cd, Co, and Sn are mainly dispersed in the river reaches of Xingtai City and pose potential health risks in midstream, as per the geoaccumulation index and Pearson's correlation analyses. In particular, Cd accumulates strongly in sediments of Ming River and Aixinzhuang dam from Xingtai City. In upstream and downstream of FRS, the potential ecological risk is low, except in Yongnian County where high ecological risk was caused by Cd and Hg. These findings provide new insights into the pollution characteristics and assessment of the potential ecological risks induced by heavy metals along FRS, which suggest new directions should strategically tend to typical pollutants control by policy formulation and taking effective measures to prevent and manage heavy metal pollution in North China.

Ultrasensitive electrochemical immunosensor based on the signal amplification strategy of the competitive reaction of Zn2+ and ATP ions to construct a "signal on" mode GOx-HRP enzyme cascade reaction.

A GOx/HRP@ZIF-90 nanomaterial is proposed by coating GOx and HRP in ZIF-90 using a bio-simulated mineralization method to improve the tolerance of the enzyme to the external environment. In the detection process, the ZIF-90 is turned on under mild conditions by the competitive reaction of ATP with Zn2+ and imidazole-2-carboxaldehyde (2-ICA), and the electrical signal of the system is amplified by the enzyme cascade reaction of GOx and HRP. Finally, based on the signal amplification strategy of the competitive reaction between Zn2+ and ATP to construct a "signal on" mode, electrochemical immunosensor of GOx-HRP enzyme-linked cascade reaction was prepared. The proposed electrochemical immunosensor shows an excellent analytical performance when detecting CA-125, with good selectivity and stability, with a detection range of 0.1 pg mL-1-40 ng mL-1 and a detection limit of 0.05 pg mL-1. The test has been performed using chronoamperometry under a constant voltage of -0.4 V. The immunosensor also shows an excellent performance when analysing human blood samples. The recovery of the immunosensor is 97.94-101.8%, with a relative standard deviation of 3.7-6.1%. The proposed sensor provides a novel idea for clinical use of GOx and HRP enzymes and a new method for the clinical detection of tumor markers.

Study on the performance of a MOF-808-based photocatalyst prepared by a microwave-assisted method for the degradation of antibiotics.

In this paper, a simple method was used to rapidly prepare MOF-808 with a large specific surface area and high stability. Bi2S3 and MOF-808 were used to design and synthesize high-stability Bi2S3/MOF-808 nanocomposites, which were then used for the photocatalytic degradation of antibiotic tetracyclines. The performance test results showed that the 0.7-808 composite material had good photocatalytic degradation performance for tetracycline under visible-light irradiation, and the degradation rate reached 80.8%, which was 3.21 times and 1.76 times that of MOF-808 and Bi2S3, respectively. This was mainly due to the high photocurrent response and photoluminescence of the Bi2S3/MOF-808 composite material. Therefore, the close contact of n-n Bi2S3/MOF-808 can transfer light-generated electrons and holes to improve the utilization efficiency of photogenerated charges, thereby greatly improving the photocatalytic reaction activity. Particle-capture experiments and ESR confirmed that ˙OH was the main active substance in the photocatalytic degradation.

A sandwich-type electrochemical immunosensor for ultrasensitive detection of multiple tumor markers using an electrical signal difference strategy.

Traditional sandwich-type electrochemical immunosensors can only detect single tumor markers because signal interference occurs when detecting multiple tumor markers. In this work, an electrical signal difference strategy was proposed for the accurate detection of multiple tumor markers. We labeled PdAgCeO2 mesoporous nanospheres with a carcinoembryonic antigen (CEA) secondary antibody and MnO2 nanosheets labeled with an alpha-fetoprotein (AFP) secondary antibody. The two electrical signal tags were mixed and incubated on a prepared immunosensor to catalyze H2O2 and generate an electrical signal I1 (i-t ampere curve). When 2.5 mM ascorbic acid solution (AA) was added to 20 mL of PBS solution at pH = 6.5 for 180 s, an electrical signal I2 was generated. I2 was the current response of the CEA antigen concentration, and the electrical signal difference ΔI = I1-I2 was the current response of the AFP antigen. Thus, the immunosensor accurately detected the AFP and CEA tumor markers. This method was called the electrical signal difference strategy. The proposed single-use immunosensor detected CEA antigens in a range of 0.001 ng/mL-40 ng/mL, and the detection limit was 0.5 pg/mL; the detection range of the AFP antigen was 0.005 ng/mL-100 ng/mL, and the detection limit was 1 pg/mL. Therefore, this study provides new ideas and strategies for accurate clinical detection of multiple tumor markers.

A sandwich-type electrochemical immunosensor for detecting CEA based on CeO2-MoS2 absorbed Pb2.

A sandwich-type immunosensor for detecting the concentration of carcinoembryonic antigen (CEA) was prepared. In this work, gold nanoparticles (Au NPs) were used as platform to attach more primary antibody (Ab1) due to excellent electrical conductivity and good biocompatibility. Molybdenum disulfide-Cerium oxide (CeO2-MoS2) nanohybrid was used as a carrier to absorb lead ions (Pb2+) and the second antibody (Ab2). CeO2-MoS2-Pb2+-Ab2 was used as a nanoprobe to detect CEA antigen. Under optimal conditions, square wave voltammetry (SWV) successfully displayed the electrical signal of Pb2+. The designed electrochemical immunosensor has excellent analytical performance. In addition, the detection range was 0.001-80 ng/mL and the minimum detection limit was 0.3 pg/mL (S/N = 3), which had good selectivity and stability. Finally, the proposed immunosensor successfully detected the concentration of CEA in the serum of the sample, which provided a feasible method for CEA testing.

Sensitive detection of carcinoembryonic antigen (CEA) by a sandwich-type electrochemical immunosensor using MOF-Ce@HA/Ag-HRP-Ab2 as a nanoprobe.

Sandwich-type electrochemical immunosensor was one of the main methods for detecting carcinoembryonic antigen (CEA). In this work, using Ce-MoF as the skeleton precursor, hyaluronic acid (HA) was coated on the surface of Ce-metal organic framework (Ce-MoF), which loaded with silver nanoparticles (Ag NPs) and horseradish peroxidase (HRP) to catalyze H2O2 and double amplified the current signal. Thus, a sensitive sandwich-type electrochemical immunosensor (Ce-MoF@ HA/Ag-HRP) was designed to detect carcinoembryonic antigen (CEA). The designed immunosensor used Au NPs to enhance the ability of attach more the first antibody (Ab1). This was due to Au NPs had good electrical conductivity and biocompatibility to accelerate electron transfer on the surface of the electrode. HA was riched in -COOH, -OH and had excellent biocompatibility, which can carry more Ag NPs to catalyze H2O2. Finally, the prepared sandwich-type electrochemical immunosensor had excellent biocompatibility and great catalytic performance. The immunosensor can be tested within 30 min and the logarithm of the current signal and CEA concentration showed a broad linear response range of 1 pg ml-1-80 ng ml-1, and the detection limit of CEA was 0.2 pg ml-1. More importantly, the proposed immunosensor had good reproducibility, selectivity, stability and without matrix effect. This confirmed that the proposed immunosensor had broad prospects in early clinical trials.

Microwave-assisted preparation of ZnFe2O4-Ag/rGO nanocomposites for amplification signal detection of alpha-fetoprotein.

In this study, a novel signal-amplified immunosensor was designed by using a microwave-assisted self-assembly method to synthesize ZnFe2O4-Ag/rGO nanocomposites. The conductivity of ZnFe2O4-rGO nanocomposites was significantly improved due to the effective inhibition of rGO accumulation by the insertion of ZnFe2O4 and Ag nanoparticles (NPs) into graphene sheets. Excellent sensitivity and reproducibility were achieved through the microwave-assisted preparation of ZnFe2O4-Ag/rGO nanocomposites as a substrate, with the Ag NPs enhancing the signal because of the effective conductive matrix. The layer assembly process of the immunosensor was verified by cyclic voltammetry and electrochemical impedance spectroscopy. Under optimal conditions, the fabricated immunosensor showed good linearity over a wide concentration range from 1 pg mL-1 to 200 ng mL-1 with a low detection limit of 0.98 pg mL-1, and exhibited excellent specificity, good stability, and reproducibility. These qualities can contribute to the successful application of a label-free immunosensor in the detection of AFP in human serum.

Sandwich-type electrochemical immunosensor constructed using three-dimensional lamellar stacked CoS2@C hollow nanotubes prepared by template-free method to detect carcinoembryonic antigen.

Effective treatment of cancer depends on early detection of tumor markers. In this paper, an effective template-free method was used to prepare CoS2@C three-dimensional hollow sheet nanotubes as the matrix of the immunosensor. The unique three-dimensional hybrid hollow tubular nanostructure provides greater contact area and enhanced detection limit. The CoS2@C-NH2-HRP nanomaterial was synthesized as a marker and had a high specific surface area, which can effectively improve the electrocatalytic ability of hydrogen peroxide (H2O2) reduction while increasing the amount of capture-fixed carcinoembryonic antigen antibody (anti-CEA). In addition, the co-bonded horseradish peroxidase (HRP) can further promote the redox of H2O2 and amplify the electrical signal. Carcinoembryonic antigen (CEA) was quantified by immediate current response (i-t), and the prepared immunosensor had good analytical performance under optimized conditions. The current signal and the concentration of CEA were linear in the range of 0.001-80 ng/mL, and the detection limit was 0.33 pg/mL (S/N = 3). The designed immunosensor has good selectivity, repeatability and stability, and the detection of human serum samples shows good performance. Furthermore, electrochemical immunosensor has broad application prospects in the clinical diagnosis of CEA.

Coral-like Co3O4 Decorated N-doped Carbon Particles as active Materials for Oxygen Reduction Reaction and Supercapacitor.

Coral reef has a unique dendritic structure with large specific surface area, rich pore structure, so that it can be attached to a large number of zooxanthellae for gas exchange. Coral reef ecosystems are also known as underwater rainforests. Inspired by this biological structure, we designed and fabricated coral-like Co3O4 decorated N-doped carbon particles (Co3O4/N-CP). The obtained Co3O4/N-CP-900 catalyst shows efficient ORR electrocatalytic performances in an alkaline medium with a positive onset and half-wave potentials of 0.97 and 0.90 V (vs. RHE), as well as a high diffusion-limited current density (5.50 mA cm-2) comparable to that of a Pt/C catalyst (5.15 mA cm-2). It also displays better stability and methanol tolerance than commercial Pt/C. In addition, the Co3O4/N-CP-900 electrode has a high specific capacitance of 316.2 F g-1 in 6 M KOH, as well as good rate capabilities and excellent cycle performance. These results are due to large surface area, narrow pore size distribution, high density electrochemical energy conversion and storage activity centers. This method presented here offers an effective path for the development of high performance multi-functional carbon-based materials for ORR and supercapacitor applications.

Graphene oxide supported rhombic dodecahedral Cu2O nanocrystals for the detection of carcinoembryonic antigen.

In this work, a simple electrochemical immunosensor was developed for the detection of carcinoembryonic antigen (CEA) based on rhombic dodecahedral Cu2O nanocrystals-graphene oxide-gold nanoparticles (rCu2O-GO-AuNPs). GO as the template and surfactant resulting in rCu2O exhibit improved rhombic dodecahedral structure uniformity and excellent electrochemical performance. Moreover, GO was found to be able to effectively improve the long stability of rCu2O on the electrode response. Under optimal conditions, the immunosensor showed a low limit of detection (0.004 ng ml(-1)) and a large linear range (0.01-120 ng ml(-1)). This work presents a potential alternative for the diagnostic applications of GO-supported special morphology materials in biomedicine and biosensors.

Distribution and factors affecting adsorption of sterols in the surface sediments of Bosten Lake and Manas Lake, Xinjiang.

This study investigated the concentrations and distribution of eight sterol compounds in the surface sediments of Bosten Lake and Manas Lake, Xinjiang, China. The ratios of sterols as diagnostic indices were used to identify pollution sources. The sediment of the two lakes was selected as an adsorbent to investigate the adsorption behaviour of sterols. Results showed that the sterols were widely distributed in the sediments of the lakes in the study areas. The total concentrations of the detected sterols in Bosten Lake and in Manas Lake were 1.584-27.897 and 2.048-18.373 µg g(-1)∙dw, respectively. In all of the sampling sites, the amount of faecal sterols was less than that of plant sterols. ß-sitosterol was the dominant plant sterol with a mean concentration of 2.378 ± 2.234 µg g(-1)∙dw; cholesterol was the most abundant faecal sterol with a mean concentration of 1.060 ± 1.402 µg g(-1)∙dw. The pollution level was higher in Bosten Lake than in Manas Lake. Majority of the ratios clearly demonstrated that the contamination by human faecal sources was occurring at stations which are adjacent to residential areas and water inlets. The adsorption behaviour of sterols to sediment suggested that the sterol adsorption coefficients were reduced as temperature increased. As salinity increased, the adsorption quantity also increased. As pH increased, the sediment adsorption of sterol slightly increased because the strong alkaline solution is not conducive to the adsorption of sterols. The ratios between sterols did not change largely with the change in external factors.

A sandwich-type electrochemical immunosensor for carcinoembryonic antigen based on signal amplification strategy of optimized ferrocene functionalized Fe3O4@SiO2 as labels.

A sandwich-type electrochemical immunosensor was developed for sensitive detection of carcinoembryonic antigen (CEA) by using ferroferric oxide@silica-amino groups (Fe3O4@SiO2-NH2) as carriers and gold nanoparticles-graphene oxide (GO-AuNPs) as platform. The Fe3O4@SiO2-NH2 surface was used as linked reagents for co-immobilization of ferrocenecarboxylic acid (Fc-COOH) and secondary anti-CEA (Ab2) to prepare the signal probe, and it also could hasten the decomposition of hydrogen peroxide (H2O2) to amplify signals. Differential pulse voltammetry (DPV) was successfully used to quantify CEA. Under the optimized conditions, the designed immunosensor shows an excellent analytical performance wide dynamic response range of CEA concentration from 0.001 ng mL(-1) to 80 ng mL(-1) with a relatively low detection limit of 0.0002 ng mL(-1) (S/N=3), and high specificity and good reproducibility. The proposed immunosensor was successfully used to determine CEA in spiked human serum samples.

An electrochemical immunosensor for simultaneous point-of-care cancer markers based on the host-guest inclusion of ß-cyclodextrin-graphene oxide.

A novel electrochemical immunosensor was developed for the simultaneous detection of alpha-fetoprotein (AFP) and carcinoembryonic antigen (CEA) using Cu2O-graphene oxide-ß-cyclodextrin (Cu2O-GO-CD) and ß-cyclodextrin-graphene oxide-ferrocenecarboxylic acid (GO-CD-Fc-COOH) as the distinguishable signal probe, and graphene oxide-gold nanoparticles (GO-AuNPs) as the sensor platform. GO-CD displayed excellent solubility in water and rich capture capability to Fc-COOH and the secondary antibody. The proposed immunosensor exhibited an excellent electrochemical performance. The linear ranges were from 0.001 ng mL-1 to 80 ng mL-1 for AFP and CEA with a detection limit of 0.0002 ng mL-1 for AFP and 0.0001 ng mL-1 for CEA. With the merits of acceptable stability, high sensitivity, a wide linear range and a low detection limit, the proposed immunosensor showed great potential for the simultaneous detection of multi-analytes in clinical diagnosis.