Study Of Biosensor Based On DNA Modified Gold Nanoparticles And Signal Amplification

In recent years, the detection of sequence-specific DNA has been widely used in clinical diagnosis, forensic science, food testing, environmental monitoring and many other fields. Researchers are increasingly interested in its detection methods and precision, since traditional methods are complex with high cost.H. pylori, colonized in the gastric mucosa of stomach illness patients, can cause chronic gastritis, gastric ulcer and even gastric cancer. So it is important to detect it rapidly and accurately for the diagnosis and treatment of stomach illness. With the rapid development of genetic diagnosis and further study of H. pylori genome, the detection of H. pylori is becoming easier, faster, and more accurate. Moreover, non-invasive detection of it has received more and more attention. Here, we design an electrochemical DNA biosensor to detect the specific sequence-UreB of H. pylori, in which APTES self-assembled molecular film and DNA-modified gold nanoparticles were used, and we used metal complexes as chemical indicator, then detect the signal electrochemicallyThe designed sensor use DNA-modified gold nanoparticles twice to double magnify the signals. The rpDNA is complementary to about a half-portion of the target DNA sequence (tDNA). A capture DNA (cpDNA), complementary to the other half of the tDNA, was immobilized on the surface of a glassy carbon electrode by the electrostatic force between the amino of APTES and phosphate groups of the capture DNA In the presence of tDNA, a sandwich structure of (hpDNA/AuNP/rpDNA)/tDNA/(cpDNA/AuNP)was formed on the electrode surface. In the study, electrochemical active Ruthenium complex pentaamin ruthenium (Ⅱ) [3-(2-phenanthren-9-yl-vinyl)-pyridine] (referred to as [Ru(NH3)5L]2+) was synthesized and used as a hybridization indicator of this DNA biosensor. [Ru(NH3)5L]2+can insert into double-stranded DNA,including hybridization sequence between probe DNA and target DNA, and the stem of hairpin DNA. Then we can perform electrochemical detection directly. Using [Ru(NH3)5L]2+can effectively reduce the detection of background current.TEM observation and UV absorption speak show that the synthesized gold nanoparticles are about 13±1 nm in diameter. Using fluorescence modified capture DNA and the AuNPs synthesize AuNPs-cpDNA composites. The result show that about 231 cpDNA was attached on each gold nanoparticle. And about 147 hpDNA and 29 rpDNA were attached on another AuNPs-hpDNA-rpDNA composite. Under optimal conditions, the low detection limit is 6x10-l8M. When the concentration of target DNA is at the range of 10-13 M～1016 M, the peak current (Ip) detected by differential pulse voltammetry (DPV) electrochemistry sensing technique and the logarithm of the concentration of target DNA are linearly correlated. And the regression equation is:Ip (10-7A)=2.16261g (CtDNA/M)+39.5352, with regression coefficient R2= 0.9966In this study,a highly sensitive and specific electrochemical DNA biosensor is developed. Future works would be focuses on optimizing the experiment condition and aim to achieve fast,simple and sensitive detection in live samples.