Sensors Based On Functional Nucleic Acid

Functional nucleic acids are a kind of nucleic acid sequences with special functions,which can specifically bind target substances or catalyze reactions. These sequences,because of their characteristics, have been demonstrated enormous potential in biologicalanalysis, food safety testing, environmental analysis, pharmaceutical testing. In this paper,we combined functional nucleic acid recognition and catalytic function, with themodification function and optical properties of nanoparticles, and established differentfunctional nucleic acid sensors systems.The first part of the experiment focus on builing aptamer and nucleic acid biosensorswith DNAzyme catalysis as the signal transduction. The catalysis of DNAzyme depends onthe formation of G–quadruplex. In the experiments, we divided nucleic acid sequencewhich formed the G–quadruplex DNA enzyme into two parts, and hybrid target aptamermodified on the surface of Au NPs then that is fixed on the Au NPs surface. After the targetis added, due to the specific binding between the adenosine and its aptamer as well asbinding between complementary sequence of DNA, the previous hybridization is brokendown, then the two part of DNAzyme has been released from surface of Au NPs, finallyafter adding the cofactor namely hemin, the combination of three lead to formation ofDNAzyme which catalyzed luminol chemiluminescence. As a result, the aptamer sensorsand nucleic acid sensors has been built in this way. Design of segmented DNAzyme caneffectively reduce background noise, importantly, the entire analysis process is carried outin a homogeneous system, that means without separation before testing and sensitivedetection.The second part focuses on detection of certain metal ions utilizing their interactionwith some specific base pairs. Two types of gold nanopartciles with DNA modificationswere assembled together through an extra linking sequence. When Hg2+or Ag+presents, they can interact with thymine and cytosine bases respectively and stabilized T-T and C-Cmismatches in the linking sequence, which further resulted in disassembly of the goldnanopaticles. Due to the effect of local surface plasmon resonance of the gold nanoparticlebefore and after the identification, there was a significant shift of the absorption profilesand related color change showed up, which provided a scheme for visualized detection ofthe ions. Furthermore, quatitative information of the ions could be obtained throughmeasureing of the UV-vis absorption. This provided a facile tool for the analysis of relatedions.