| With the revolutionary developments of Human Genome Project, we are entering a new era of scientific discovery that holds great promise for understanding the complexities of the life. But genome sequencing is only the first step toward achieving an understanding of gene and the following problems we encounter are to make out expression and functions of the sequence-known gene and how they affect the human life, health and disease. Hence, the research on the interaction of DNA with other molecules is significant without question. On the other hand, DNA probe-based biosensors or biochips play a very important role in genome research field and the various applications, such as molecular diagnostics and environment monitoring. Diverse DNA sensors or chips, which can offer faster, higher-throughout or cheaper gene detection, are needed to meet the growing demands.The immobilization of DNA on surface, especially on conductive surface, is of great interest and important both in studies of DNA sensors or chips and in various other applications. To construct stable DNA sensors or chips, DNA probes must firstly be anchored to a surface to form a DNA recognition layer and subsequently used to detect its complementary sequences.In this work, a new method of DNA immobilization has been developed. Cationic FDD A, which was found to adhere strongly to variety surfaces, was used to facilitate DNA immobilization on the gold surface. It wasconceivable that immobilization of the negatively charged DNA onto ordered 旾V-positively charged PDDA cations adlayer on the gold surface was greatly facilitated by strong electrostatic interactions. Spectra of Diffuse Reflectance FT-IR (DRFT-IR), X-ray Photoelectron (XPS) and Raman spectroscopy confirmed the immobilization of calf thymus(CT) DNA on electrodes modified by PDDA. STM images of the PDDA self-assembled film manifest the structure of two-dimensional close-packed ordered lines array (2~3nm in width) and the subsequently adsorped DNA strands were immobilized along the direction of PDDA "lines array", which were also ordered to some extent, and some hanging and winding segments of DNA strands form the some convexity on STM image.We also introduced Cationic polyelectrlyte梡oly(ethylenimine) (PEI) to form a self-assembly monolayer on gold surface and use it to immobilize DNA onto surface. The measurements of XPS, FT-IR and Raman were used to characterize the immobilization of DNA. The results showed that it's also a proper way to anchor DNA onto surface. STM images showed that the structure of PEI self-assembled monolayer is a flat film with many holes (3~6nm in diameter), somewhat like pinholes on n-alkylthiol self-assembled monolayer.In balancing the performance of two cationic polyelectrolyte self-assembled monolayers(SAMs) and their exercises on immobilization of DNA, PDDA SAMs seemed rather to preponderate on the orientation and electron transfer. Though PEI SAMs proved to be a proper substrate candidate to anchor DNA onto it.Meanwhile, we introduced another new method to construct high-density DNA array using anodic aluminum oxide(AAO) template. XPS,DRFT-IR, Raman and AFM methods were exploited for characterization.PDDA SAMs was employed to investigate the interaction of [Co(phen)3]3"'7" with double-stranded(ds) DNA and single-stranded(ss) DNA. The different mode of interaction of ssDNA and dsDNA with [Co(phen)3]3+/2+ was discussed. The results indicated that PDDA SAMs was a seemly substrate to study the interaction of DNA with other molecules. On the basis of the different electrochemical response resulted from different interaction of [Co(phen)3]3+/2" with dsDNA and ssDNA, the electrochemical labeling of DNA hybridization was proposed, i.e., the hybridization can be detected according to the current change of electroactive label at specific potential, which was likely to be used to fabricate electric read-out DNA sensors or chips. The resultes also showed that combined with [Co(phen)3]3+/2" as electroactive label PDDA SAMs could be used...
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