Ratiometric electrochemical immunosensor for the detection of CA199 based on the ratios of NiCo@Fc-MWCNTs-LDH and 3D-rGOF@Ag/Au complexes.

Carbohydrate antigen 199 (CA199) is the most sensitive marker reported for pancreatic cancer, and it is a difficult task to develop a highly sensitive assay for CA199. During the experiment, a ratiometric electrochemical immunosensor for quantitative analysis of CA199 was prepared for NiCo@Fc-MWCNTs-LDH as the electrode sensing surface and 3D-rGOF@Ag/Au as the label of Ab2. NiCo@Fc-MWCNTs-LDH not only provide the required signal for the immunosensor, but also have a layered structure to obtain a large specific surface area, which can provide more sites for the placement of biological molecules. rGOF has the advantages of large specific surface area and high porosity, which can adsorb Ag electrochemical probe through redox reaction. The modification of gold nanoparticles can not only enhance the electrical conductivity of nano-composites, but also immobilize more biomolecules to improve the sensitivity of electrochemical sensors. With the beefing up of CA199 concentration, the oxidation peak current of Ag increases and the oxidation peak current of Fc-COOH decreases. The ratio (y = IAg/IFc-COOH) of two different signals was linear with the logarithm of CA199 concentration in a certain value range. Under optimal conditions, the immunosensor showed excellent performance in the concentration range of 0.0001 U/mL to 10 U/mL, and the detection limit was 5.55 × 10-4 U/mL. The strategy could clearly discriminate between matched and mismatched targets, demonstrating high specifificity. This approach further detects CA199 in human plasma to differentiate pancreatic cancer patients from healthy individuals with high accuracy. This method also provided a new idea for the ultrasensitive quantitative detection of other biomarkers.

A Novel Electrochemical Immunosensor Based on COF-LZU1 as Precursor to Form Heteroatom-Doped Carbon Nanosphere for CA19-9 Detection.

Porous carbon sphere materials have a large variety of applications in several fields due to the large surface area, adaptable porosity, and good conductivity they possess. Obtaining a steady carbon sphere using the green synthesis method remains a significant challenge. In this experiment, covalent organic frameworks (COFs) were used as a precursor and Fe3O4NPs were integrated into the precursor in order to synthesize a porous carbon sphere material using the one-step pyrolysis method. COFs have an ordered porous structure, perpetual porosity, large surface area, and low density and display good environmental tolerance. These properties make them an excellent precursor for synthesizing porous carbon sphere, which maintains good morphology at high temperatures, and it is not involved in the removal of dangerous reagent and small size restrictions during the synthesis process. In addition to the formation of a porous carbon sphere, transition metal carbon material that contains N element can be an active catalyst. The composites exhibit better activity when Fe is doped into carbon materials containing N element than that of other doped transition metals including Mn and Co. In this situation, the integration of Fe3O4NPs and N element in the COF precursor exposed the active sites of the composites and the two substances synergistically improved the electrocatalytic properties, and the composites were named Fe3O4@NPCS. The constructed Fe3O4@NPCS/GCE immunosensor was applied as a means of detecting CA19-9 antigen and presented a wide linear range from 0.00001 to 10 U/mL with a low detection limit of 2.429 µU/mL (S/N = 3). In addition, the prepared immunosensor was utilized for detecting CA19-9 antigen in the real human serum, and the recovery rates were in the range from 95.24% to 106.38%. Therefore, a porous carbon sphere prepared by COFs as a precursor can be applied for the detection of CA19-9 antigen in real samples, which could be an excellent strategy for CA19-9 antigen detection and could potentially promote the development of COF materials in various electrochemical fields.

A label-free electrochemical immunosensor for CA125 detection based on CMK-3(Au/Fc@MgAl-LDH)n multilayer nanocomposites modification.

A label-free electrochemical immunosensor was constructed for cancer antigen 125 (CA125) detection based on multiple-enlargement means of layer-by-layer (LBL) assembly of ordered mesoporous carbon (CMK-3), gold nanoparticles (Au NPs) and MgAl layered double hydroxides containing ferrocenecarboxylic acid (Fc@MgAl-LDH). A CMK-3(Au/Fc@MgAl-LDH)n multilaminate nanocomposites was designed using technology of LBL self-assembly among negatively charged Au NPs, positively charged CMK-3 and Fc@MgAl-LDH nanosheets. The CMK-3(Au/Fc@MgAl-LDH)n multilaminate nanocomposites was used as carriers to increase the immobilization of antibody and the number of loading Fc, conductors to strengthen conductivity and enhancers to amplify signal of Fc step-by-step. Besides, this special and excellent way of LBL assembly can immensely amplify the signal of immunosensor and more immobilize the biomolecules, and label-free method is a more simple the measuring way and the procedure. The immunosensor displayed a wider linear range of 0.01 U ml-1-1000 U ml-1 and a lower detection limit of 0.004 U ml-1. Therefore, the sensor can stablely and accurately be applied for CA125 detection in clinical cancer diagnosis.

Electrochemical Detection of Nuciferine in the Lotus Leaf Based on Efficient Catalysis by Zirconium-MOFs.

BACKGROUND: Nuciferine is an amorphine alkaloid in lotus leaf that has anti-inflammatory, lipid-lowering and hypoglycemic effects, so the quantitation of detected nuciferine is important. OBJECTIVE: An electrochemical method was developed for nuciferine detection based on efficient catalysis by Zr-MOFs (Metal-organic frameworks). METHODS: In this work, the ratiometric electrochemical method was developed for nuciferine detection based on efficient catalysis by Zr-MOFs. UiO66 is a Zr-MOFs nanomaterial and can absorb methylene blue (MB) by electrostatic action to form UiO66-MB nanocomposite. The UiO66-MB nanocomposite can be used as an enhancer to catalyze nuciferine decomposition and a carrier to provide a two-dimensional environment for the reaction of nuciferine. Moreover, good catalytic properties of UiO66 were first time used for the detection of nuciferine. RESULTS: This method has a linear detection range from 0.1 to approximately 20 µg/mL, and a low detection limit of 0.03 µg/mL (S/N=3). The recovery was from 98.1 to 102% and the RSD was from 0.45 to 3.65%, indicating that the proposed method can be applied for the analysis of real samples. CONCLUSION: The proposed electrochemical method can be used to detect nuciferine in lotus leaves. HIGHLIGHTS: The ratiometric electrochemical method was used for the detection of nuciferine. The MB can be used as an internal standard for anti-interference. And, UiO66 is used to catalyze the decomposition of nuciferine. Great catalytic properties of UiO66 were first time used for the detection of nuciferine.