The Designs And Investigations Of Electrochemical Biosensors For The Detection Of XIAP-BIR3and BPA

Electrochemical biosensors, as a type of analytical technique, have been intensively investigated and widely applied in recent years. The basic principle of electrochemical biosensors is transforming the specific recognition of the immobilized probe into a measurable electrochemical signal, without the requirement of professional operators and expensive equipments. Electrochemical biosensors combine the selectivity of biological reactions and the sensitivity of electroanalytical technique, owning the advantages such as quick response, low cost and easy-to-operate. In order to simplify the fabrication and detection procedure of biosensor, this work developed two reagentless and label-free electrochemical biosensors by one single electrochemical polymerization step, for the detection of big biomolecules (protein) and small organic molecules (endocrine disruptor), respectively. The proposed biosensor platform has high selectivity, specificity and sensitivity.This dissertation (1) first introduces the essential principles, including the basic elements in electrochemical biosensors and various detection modes; then the conducting polymers applied in electrochemical biosensors are reviewed. The original electrochemical biosensor platform based on copolymerization of5-hydroxy-l,4-naphthoquinone (juglone) and its derivatives is also proposed.(2) presents a electrochemical biosensor based on a juglone-peptide conjugate (AVPFAQK(JugAcid)G, JP), for the detection of the protein cancer biomarker XIAP-BIR3. The electrosynthesized copolymer film, poly(Jug-co-JP), is quite stable and shows well-defined electrochemical activity in PBS. The attachment of XIAP-BIR3on the polymer/solution interface through specific peptide-protein interactions leads to a large increase in steric hindrance which related to the redox reaction from quinone, therefore a current decrease (signal-off) can be observed, through which XIAP-BIR3can be detected directly. The results show that the current change has a linear relationship with lg([XIAP-BIR3]), with a limit of detection of lnM (13ng mL"1). It’s also found that the XIAP-BIR3attached on poly(Jug-co-JP) can be dissociated by adding free AVPFAQKG peptide, inducing a signal-on response, while the addition of modified and unrelated peptide can’t recover the electrochemical signal. Moreover, non radioactive tests related to peptide sequences design, protecting group selection, organic synthesis conditions and the affinity to target protein were involved in this part, which provide valuable synthesis experiences and data for the radioabeling of peptides in XIAP-BIR3targeting cancer drugs.(3) fabricates a reagentless and label-free electrochemical immunosensor to detect bisphenol A (BPA). The immunosensor based on the electropolymerization of a functional monomer, N-(3-(4-(2-(4-hydroxyphenyl)propan-2-yl)phenoxy)propyl)-3-(5-hydroxy-l,4-dihydro-l,4-dioxonaphthalen-2(3)-yl)propionamide (JugBPA). Square Wave Voltammetry shows that the electrochemical signal of the conducging copolymer film, poly(Jug-co-JugBPA) provides a "signal-off" response upon anti-BPA binding, and a "signal-on" response upon BPA addition in solution. This functional conducting polymer based immunosensor shows good sensitivity (limit of detection of2pg mL-1) and high selectively for BPA detection, consider the negative control experiments carried out by two related compounds (bisphenol A dimethacrylate and dibutyl phthalate). This immunosensor platform would be a great advance for small organic molecule detection in environmental monitoring, food control and other fields.