Construction Of Electrochemical Immunosensors Based On Bimetallic Nanomaterials And Their Applications In The Detection Of Tumor Markers

Cancer is currently the leading cause of death worldwide,and the number of cancer patients is expected to continue to increase over the next 50 years.Tumor biomarkers are one of the most valuable tools for timely detection of cancer and monitoring the progression of this disease.Protein tumor markers in serum are proteins associated with malignant tumors produced by tumor tissue or host reaction with tumors,which can reflect and evaluate the occurrence and development of tumors.Electrochemical（EC）immunosensors integrate the unique advantages of electrochemical procedures,specific immune recognition reactions,and biosensor devices.It is an ideal immunoassay platform for quantitative detection of tumor markers.It has the advantages of simple method,easy miniaturization,strong selectivity,high sensitivity,wide detection range and low detection limit.Therefore,EC immunosensors have been widely studied in detecting tumor markers.Because of the above content,based on the classic sandwich structure,two EC immunosensors are designed in this paper.Bimetallic nanomaterials with excellent electrochemical performance and simple preparation method were used to amplify the detection signal,so as to achieve more accurate detection and analysis of tumor markers.The main research content of this paper is as follows:（1）Herein,Pt Ru nanoassemblies（NAs）were synthesized via a facile one-step solvothermal approach,with the help of octylphenoxypolye thoxyethanol（NP-40）acted as a growth-directing molecule,and triethylene glycol（TEG）worked as a reductant and solvent.Pt Ru NAs is formed by the accumulation of small particles,and a large number of voids are formed in the assembly process of small particles,which significantly increases the specific surface area of Pt Ru NAs and shows excellent electrocatalytic performance.A simple signal-enhanced EC immunosensor was constructed by combining Pt Ru NAs as an amplifier of the oxidation signal of potassium ferricyanide（K₄[Fe（CN）₆]）with the specific recognition process of antigen-antibody.Verified by a series of experiments,the proposed immunosensor presented a wide linear range(10^-4-70 U m L^-1)and a low detection limit(3.3×10^-5 U m L^-1),accompanied by good reproducibility,selectivity,and stability,which could be applied in human serum samples for the determination of CA199.The results were similar to commercial electrochemical luminescence（ECL）immunoassay.Feasibility of batch fabrication of Pt Ru NAs makes nanomaterial-based EC immunoassay promising for the determination of similar cancer markers in future.（2）A novel ratio EC immunosensor for CEA detection was constructed.It uses chitosan-ferrocenecarboxaldehyde-gold nanospheres（Chi-Fc-Au）and reduced graphene oxide-Pd@Au nanocomposite-thionin（rGO-Pd@Au-Thi）for dual-signal mode output.The immunosensor utilized Chi-Fc-Au as the substrate to anchor the primary antibody（Ab₁）and rGO-Pd@Au-Thi as the secondary antibody（Ab₂）label probe.In the presence of CEA,two electrical signals(I_Fc and I_Thi)from Fc and Thi respectively can be generated.With the increase of CEA concentration,the I_Fc and I_Thi showed opposite changes,so the peak current ratio of I_Thi/I_Fc was positively correlated with CEA concentration.Compared with other immune sensors,especially those in single signal mode,the accuracy of the constructed sensor is significantly improved,with a wider linear range(10^-4-200 ng m L^-1)and a lower detection limit(14.9 fg m L^-1).It can be used for the detection of CEA in human serum samples,and the detection results are comparable to commercial ECL immunoassay results.Given the significantly improved accuracy of the constructed sensor,it is expected to be applied in clinical diagnosis for other protein biomarkers determination.