The Study Of Biosensor Based On DNAzyme-Aptamer

DNAzyme is a small DNA sequence which can combine with hemin and then catalyze ABTS2- to the ABTS-product by H2O2. DNAzyme always acts as amplifying labels as being a complex of a single-stranded DNA and hemin. Aptamer is a single and short nucleic acid sequence, either DNA or RNA. Based on the characteristic of aptamer and DNAzyme, two kinds of biosensors were designed to rapid detect adenosine triphosphate (ATP) and thrombin, respectivily. This thesis mainly includs following parts:1. The construction of biosensor for ATP detection.A biosensor to rapid and specific detect ATP was constructed based on the change of conformation of ATP and aptamer, and DNAzyme was acted as amplifying label.Two sequences were designed. As a functional chain, the first chain included two parts, the left end was the ATP aptamer and the right end was DNAzyme. As a block chain, the second chain can be hybridized by the first chain partly. After the two chains hybridized completely, the left end of the hybrid chains was opened as soon as ATP was added into the solution. As the same way, the right end was unfolded by the added hemin. So the hybrid chains were separated thoroughly in this way. The complex of DNAzmye and hemin catalyzed ABTS2- to the ABTS- by H2O2, ABTS were deoxidized and then caused chemical luminescence, the change of absorbance value can be observed in 414 nm by UV Spectrophotometer.2. The construction of biosensor for thrombin detection.A biosensor to rapid detect thromin was constructed based on the change of conformation of thrombin and Aptamer, and DNAzyme was acted as amplifying label.Compared with ATP biosensor, the sensor was clearly different in their two chains. The third chain included two parts:thrombin aptamer in left end and the complementary chain of DNAzyme in right end. Correspondingly, the fourth chain included two parts:complementary chain of thrombin aptamer in left end and DNAzyme in right end. After the two chains were hybridized completely, the left end of the hybrid chains was opened as soon as thrombin was added into the solution. At the same way, the right end was unfolded by the hemin. The complex of the DNAzyme and hemin catalyzed ABTS2to the ABTS- by H2O2, and then the change of absorbance value was observed in 414 nm by UV Spectrophotometer.