A Study Of The Novel Label-free Electrochemical Aptamer Biosensor

Aptamers are a kind of single-stranded DNA or RNA oligonucleotides, which areselected from systematic evolution of ligands by exponential enrichment (SELEX) and canhighly specificly bind with the target molecule. Compared with antibody, aptamers have manyadvantages. In recent years, much attention has been drawn on the biosensor technologybased on the specific binding between protein and aptamers. Among them, the label-freeaptamer biosensor becomes a focus of research for good signal and low cost.In this dissertation, novel label-free electrochemical aptamer biosensors with poly(thionine) and hexacyanoferrate as redox electrochemical probes were fabricated usingthrombin and adenosine as vital models. And, the properties and application of biosensorswere discussed. The details are as following:(1) A label-free aptamer biosensor was fabricated on the surface of glassy carbon electrodewith the electropolymerized poly (thionine) as a redox electrochemical probe and goldnanoparticles as the immobilization matrix for aptamer. Electrochemical impedancespectroscopy was used to monitor the self-assembly process of the aptamer biosensor. Theelectrochemical behavior of the aptamer biosensor was studied by the cyclic voltammetry(CV) and differential pulse voltammetry (DPV). The biosensor shows a good linear range of1.0pg/mL~500ng/mL for thrombin, R=0.998, with a detection limit of0.38pg/mL (S/N=3).And the biosensor shows a good linear range of1.0pg/mL~1.0μg/mL for adenosine,R=0.9986, with a detection limit of3.8pg/mL (S/N=3).(2) label-free aptamer biosensors were fabricated on the surface of glassy carbon electrodewith the electrodeposition of metal hexacyanoferrates as a redox electrochemical probes andgold nanoparticles as the immobilization matrix for aptamers. Electrochemical impedancespectroscopy was used to monitor the self-assembly process of aptamer biosensors.Electrochemical behaviors of aptamer biosensors were studied by CV and DPV. When cobalthexacyanoferrate as the probe, the biosensor shows a good linear range of1.0pg/mL~1.0μg/mL for thrombin, R=0.998, with a detection limit of0.28pg/mL (S/N=3). When nickelhexacyanoferrate as the probe, the biosensor shows a good linear range of1.0pg/mL~1.0μg/mL for thrombin, R=0.998, with a detection limit of0.24pg/mL(S/N=3).(3) In order to enhance the electron-transfer, gold nanoparticles were electrodeposited onthe surface of glassy carbon electrode before nickel hexacyanoferrate electrodeposition. Withgold nanoparticles as the immobilization matrix for the aptamer, the thrombin aptamer wasimmobilized on the electrode surface. And then it was hybridized with the adenosine aptamer.A novel label-free aptamer biosensor for the detection of thrombin and adenosine was fabricated. The electrochemical behavior of the aptamer biosensor was studied by CV andDPV. The biosensor shows a good linear range of1.0fg/mL~1.0μg/mL for thrombin,R=0.996, with a detection limit of0.27fg/mL (S/N=3). And the biosensor shows a goodlinear range of10fg/mL~1.0ng/mL for adenosine, R=0.997, with a detection limit of0.36fg/mL (S/N=3).