Research Peptide Biosensor Electrochemical Impedance

Acute myocardial infarction (AMI) is a serious threat to human health and the incidence is rising worldwide. The biomarker troponin I (TnI) is of great use in the early diagnosis of AMI. And thus development of simple, specific and rapid method for the detection of troponin I greatly contributes the early treatment, the study of the disease source, the gene and drugs. A biosensor, which consist of the molecule recognition element(such as enzyme, antibody and single-stranded DNA) and the signal conversion element, is a powerful tool for the modern analysis. It has a lot of advantages, such as good selectivity, high sensitivity, speed of analysis, low cost, simple operation. Among all the traditional molecule recognition element, enzyme and antibodies are relatively expensive and complex to produce, costing a long time to immobilized and preservation, and easy to lose activity. By the way, the requirement of both environment and sample conditions are relatively high.Short linear binding peptides obtained using phage display show great promising in the development of novel biosensor compared to other more complex affinity scaffolds such as antibodies. Small binding peptides can be created synthetically in a reliable and cost-effective manner. Additionally, their lack of three-dimensional structure allows them to function in harsh environments. Peptide as the recognition molecule in the study of biological sensing method has already got extensive attention.The aim of the present thesis is to develop highly sensitivie and selective electrochemical impedance biosensors for the detection of biomarker proteins, In the present work, peptide was taken as the recognition molecule and the biomarker TnI was taken as a model target analyte.This thesis includes two parts, review and research work.For the first part, the review, both the structure and the classification of the biosensor, the peptide and the selecting methods of the peptide as recognition molecule, and the electrochemical impedance spectroscopy were simple introduced. The research progress of peptide-based electrochemical biosensors was reviewed. Finally, the background and content of this research work were presented.The second part includes two research chapters. In the Chapter2, the development of electrochemical impedance biosensor for the detection of TnI was described. The peptide, which has a sequence of CFYSHSFHENWPSK, was used as recognition molecule for specific target TnI in this work. Electrochemical experiments shows that the limit of detection (LOD) of our sensor(LOD=3.4×10-12g/mL, S/N=3) is at least2orders of magnitude lower than those have be reported. Meanwhile do some research to find the most suitable electrochemical impedance spectroscopy analog circuit for the model based on this biosensor. The obtained analog circuit analog error could be controlled below1%. It was found that gold nanopartials as a platform for the immobilization of recognition molecule element peptide can reduce the background EIS signal and enhance the increased EIS response. Thus EIS could been widely used in the detection of TnI since it is regarded as a label-free technique. These results demonstrate that peptides are hopeful probes in biosensor development. The designed electrochemical sensor having the characteristics of a fast response, a short binding time and a highly selectivity. This work demonstrates that EIS technique incorporating peptide as molecular recognition element is promising for development of label-free electrochemical biosensor for the determination of special proteins.Secondly, this work describes a electrochemical impedance biosensor for the detection of troponin I using peptide as the recognition molecule element based on double covalent coupling method. Double covalent coupling method and the regeneration are the innovation of this work. The chosen peptide sequence is CFYSHSFHENWPSK, which is used to establish electrochemical impedance analysis method to detect TnI. Studying the influence of different fixing methods to the various aspects of performance of the sensor. The results show that, selecting the appropriate conditions to could achieve the purpose of TnI quantitative detection. At the same time, this method could increase the detecting sensitivity and the LOD of the TnI7.91×10-12g/mL. The research showed that: the sensor interface based on4-aminobenzenesulfonic acid-modified glassy carbon electrode, could fixed amino polypeptide chain and improved the sensitivity of the electrochemical impedance sensor to the determination of TnI. Meanwhile, the electrochemical impedance technique is an effective method to study the interaction between the peptide and TnI on4-aminobenzenesulfonic acid-modified glassy carbon electrode.