Electrochemical Sensing Analysis Of Small Biomolecules Based On Electroactive Silver And Copper Oxides

Biomolecules are an important part of living organisms and play an important role in health and disease.In normal life forms,biomolecules are involved in helping to react with biological activities,but if there is an abnormality in the living body,the content of these biological molecules will be out of balance.Therefore,it is very meaningful and accurate to analyze and identify biomolecules quickly and accurately,and it is also very challenging.In recent years,with the development of various electrochemical biosensors,a class of biosensors based on electroactive nanomaterials is attracting widespread attention.In this manuscript,we study the electrochemical properties of precious metal silver and semiconductor copper oxide,and use it as a beacon to detect biomolecules.main tasks as follows:1.A novel ingenious and ultrasensitive chiral electrochemical transducer is proposed for the tryptophan?Trp?isomers detection by using electroactive Au@Ag NPs as electrochemical tags.Moreover,the large binding constant of D-Trp on NPs and strong interaction between D-Trp and Cu²⁺cause electroactive Au@Ag NP to assembly on the electrode,generating strong differential pulse voltammetry?DPV?signals from the oxidation of Ag⁰ to Ag⁺.In sharp contrast to D-Trp,L-Trp leads to the assembly of Au@Ag NP oligomers on electrode,resulting in a weak DPV signal.The distinct DPV responses enable the developed electrochemical chiral transducer for the sensitive and accurate quantification of D-/L-Trp.The limit of detection?LOD?is 1.21 pM for D-Trp.This established electrochemical chiral sensor also achieves the specific determination of enantiomeric excess.In comparison to other reported approaches,this proposed electrochemical chiral sensor excels by its sensitivity,simplicity and good availability of electroactive Au@Ag NP assemblies.Target-induced colorimetric assays can be converted into electrochemical assays for the dual signal amplification in the field of ultrasensitive enantioselective chiral discrimination.2.A simple and accurate magnetic electrochemical sensor is developed for the ultrasensitive chiral recognition of D-amino acids?D-AAs?.Fe₃O₄@Au@Ag@Cu_xO NPs are controllable prepared and used as the electrochemical beacons.The controllable integration of plasmonic metal NPs,semiconductors and magnetic NPs enables multilayered Fe₃O₄@Au@Ag@Cu_xO NPs to display a sharp copper stripping peak at-0.16 V,due to the electron transfer from Cu⁺to Cu²⁺.The signal is about 8.9 and 2.4 times higher than that of Fe₃O₄@Cu_xO NPs and Fe₃O₄@Au@Cu_xO NPs,owning to the synergistic electron transfer of Au and Ag double layers.D-AAs can be catalyzed by D-amino acid oxidase?DAAO?to produce H₂O₂.The autocatalytic oxidation reaction of Cu_xO shell with the existence of H₂O₂ induces the decrease of electrochemical signals of Fe₃O₄@Au@Ag@Cu_xO NPs.Fe₃O₄@Au@Ag@Cu_xO NPs served as electrochemical beacons achieve the sensitive and accurate enantioselective recognition of D-alanine?D-Ala?in the range from 100 pM to 10?M.The limit of detection?LOD?is as low as 52 pM.This developed protocol can be extended to the fabrication of a large set of electroactive labels by the introduction of plasmonic metal NPs with high electron transfer efficiency,for the reliable enantioselective recognition with high sensitivity.3.In view of the influence of Cu₉S₈ generated by the redox reaction between Cu₂O and hydrogen sulfide on the electrochemical properties,we designed a sensor using Cu₂O as a stable electrochemical beacon to detect endogenous H₂S.And the introduction of rGO/Fe₃O₄ on the sensor not only improves the electronic conduction rate of the sensing platform but also simplifies the sensor construction process.The changes of elements and morphology before and after the reaction between Cu₂O and H₂S were characterized by XRD,TEM and XPS.Moreover,compared with the existing MB method,the electrochemical bio-platform constructed has a detection limit of 230 pM and a detection range of 500 pM-100?M.4.Based on the results in the previous chapter,it is found that rGO/Fe₃O₄/Cu₂O has stable electrochemical response signals and basic characteristics as reference signals.We synthesized Ag@RF NPs with an organic polymer shell,and Ag nanoparticles were formed through in-situ reduction between the Ag and RF shells in the ammonia and oxygen atmosphere.Finally,Ag@RF-Ag NPs were formed and produce a stable electrochemical response as a detection signal.The PSA aptamer and Ag@RF-Ag NPs are linked by a strong covalent bond between-SH and Ag,and the PSA aptamer and the graphene nanolayer are assembled by?-?stacking.The electrochemical sensor has an anode stripping peak of Cu₂O and Ag,which cannot affect each other in the scanning range.When PSA is added,the aptamer has a better specific binding to the PSA,causing the Ag@RF-Ag NPs to fall off the electrode surface.Therefore,as the detection signal,the oxidation peak current of Ag decreased gradually with the increase of PSA concentration,while as the reference signal,the Cu₂O signal remained unchanged.And the ratio sensor has better stability and accuracy.