The Study Of Label-Free Electrochemical Aptasensor

Aptamer is a kind of oligonucleotide sequence which can specifically recognize the target and be screened in vitro. It is a potential replacer of traditional enzyme linked immunosorbent assays to analyze target. As a wide report model molecule, the aptamer of thrombin have many methods to build biosensor. But most of aptsensor are based on the optical, electrochemical label while label-free aptsensor are one of the hotspots in the research. In this thesis, three label-free electrochemical aptsensors were structured. The main works are as follows:1. Thrombin is the study object and we establish a label- free method of double signal detection of thrombin. Based on the different binding force of two indicators to different structure of DNA, we established a method to detect thrombin by the structure change of thrombin aptamer which due to the signal change. The method is simple, efficient, low cost, obvious signal changes. The aptasensor is expected to be used in the detection of thrombin in the actual samples. It also provides a new way to structure other aptasensor by the change of the aptamer.2. Based on the high specific surface area of gold nanoparticles and the conductivity of reduced graphene oxide(RGO), we established a label- free aptasensor which based on the electrochemical property of nile blue and RGO/Au NPs modified electrode. The aptasensor is easy to prepare and high sensitivity. At the same time, We get the conclusion that one-step electrodeposition reduced graphene oxide and gold nanoparticles is better than two-step electrodeposition reduced graphene oxide and gold nanoparticles or drops of coating Au NPs. What’s more, the process of preparing modified electrode is simpler and easy to repeat. Furthermore, we predict that there is a wide application for one-step electrodeposition reduced graphene oxide and gold nanoparticles in biosensor.3. Based on the scanning electrochemical microscopy, we construct a label- free biosensor to detect thrombin. The method could capture the signal change of modified electrode before and after adding thrombin. At the same time, we simply discussed the dynamic process of the biosensor. This method is simple, effective and easy to repeat. While it can provide a method to study biosensor and a new measure to detect biomacromolecule like protein and DNA.