Construction Of Electrochemical Sensors Based On Silver Nanomaterials Etching And Application In Disease Markers

A disease marker is a parameter that objectively evaluates the state of disease development.Detection of disease markers can determine whether the human body is in a normal physiological state.However,disease markers are often mixed with other complex components in the human body at very low concentrations,which makes the detection very difficult.Therefore,the establishment of detection methods with high sensitivity and strong anti-interference ability is of great significance for the diagnosis and treatment of diseases.Electrochemical sensors are a type of device that can convert the detection signal of a target into electrical signal.It is also the most widely used and earliest researched sensor.It has the advantages of high sensitivity,simple and convenient use,and fast response speed.These advantages make it develop rapidly in various fields such as heavy metal ion,pesticide residue and disease markers.So,several electrochemical sensors were prepared based on combining silver nanomaterial etching with signal amplification methods,which were applied to the detection of disease markers.This article mainly includes the following parts:1.A uric acid electrochemical sensor based on signal conversion amplification was constructed,which combined with silver nanoflowers etching and enzyme-catalyzed signal amplification strategies.The silver nanoflowers on the surface of glassy carbon electrodes were deposited by means of electroreduction.And the silver nanoflowers can be etched by hydrogen peroxide produced by the reaction of uric acid and uricase.The detection signal of uric acid was converted into the electrochemical signal of silver nanoflowers on the electrode surface and the detection of uric acid was realized.At the same time,the linear sweep voltammetric peak current value of silver nanoflowers has a good linear relationship with the uric acid concentration in the range of 1.0～100μmol/L.The detection limit of UA is 1.0μmol/L.Moreover,the method has been successfully applied to the detection of uric acid in human serum,which has broad application prospects in the diagnosis of diseases.2.Gold-silver nanoparticles and reduced graphene oxide-modified glassy carbon electrodes（Ag NPs/Au NPs/r GO/GCE）were prepared.A signal conversion amplification strategy was constructed based on this electrode,which was further applied to establish a highly sensitive alkaline phosphatase（ALP）electrochemical biosensor.The substrate L-ascorbic acid-2-phosphate ester（AA-2P）can be catalyzed by ALP to produce L-ascorbic acid（AA）,and AA can reduce iodate ion（IO₃^-）to iodine（I₂）,I₂further reacted with silver nanoparticles on the surface of the working electrode to generate silver iodide（Ag I）.ALP was quantified using the amount of silver remaining on the surface of the working electrode.The detection limit of this method is 0.11 U/L.Based on this,it was further combined with immunomagnetic separation technology to detect carcinoembryonic antigen（CEA）.During the detection of CEA,streptavidin-labeled alkaline phosphatase（SA-ALP）was used as a signal marker,and immunomagnetic beads were used as solid phase carriers.A sandwich structure was formed on the surface of the magnetic beads by antigen-antibody reaction.Finally,CEA can be detected by the conversion between the enzyme-catalyzed signal of ALP of immunomagnetic beads and the electrical signal of silver on the electrode surface.This method combined with immunomagnetic separation technology,has the advantages of high sensitivity（detection limit:0.013ng/m L）,strong anti-interference ability and wide linear range（0.10-10⁵ng/m L）.And it also has broad application prospects in the diagnosis of disease markers.3.A signal-enhanced carcinoembryonic antigen（CEA）electrochemical sensor was constructed based on the combination of dual-enzyme signal conversion strategy,silver nanoparticle etching and dual-function magnetic nanoprobe（bi-MBs）signal amplification.The bi-MBs were prepared by the specific reaction between biotin and avidin to load CEA antibody and catalase（CAT）simultaneously on the surface of avidin modified magnetic beads.During immunoassay,CEA and bi-MBs formed an immune sandwich complex on 96-well plates.CAT on the magnetic beads surface can catalyze the decomposition of H₂O₂in the detection solution,thereby inhibited the etching of silver nanoparticles on the surface of the working electrode by hydroxyl radicals generated from horseradish peroxidase（HRP）catalyzed H₂O₂.Finally,the electrochemical signal of silver on the surface of the working electrode can be used to detect CEA.Enzyme and antibody were simultaneously loaded on magnetic beads to increase the loading of enzyme and antibody,and then the detection signal is amplified.In addition,the hydroxyl radicals generated by H₂O₂can etch the silver nanoparticles on the electrode surface,and CAT can catalyze the decomposition of H₂O₂.Therefore,the dual-enzyme coupling of HRP and CAT can be used to convert the declining signal-based etching reaction into a signal enhancement-based inhibitory etching reaction.And it successfully converts the enzyme-catalyzed signal into the electrochemical signal of silver,which further performing the detection signal amplification.The minimum detection limit of this method is 0.022 ng/m L,which can be used to detect CEA in human serum.